[Qemu-devel] [PATCH v3 0/8] xen: xen-domid-restrict improvements

[Qemu-devel] [PATCH v3 0/8] xen: xen-domid-restrict improvements

[Ian Jackson]

I have been working on trying to get qemu, when running as a Xen
device model, to _actually_ not have power equivalent to root.

I think I have achieved this, with some limitations (which are
discussed in my series against xen.git.

However, there are changes to qemu needed.  In particular

 * The -xen-domid-restrict option does not work properly right now.
   It only restricts a small subset of the descriptors qemu has open.
   I am introducing a new library call in the Xen libraries for this,
   xentoolcore_restrict_all.

 * We need to call a different function on domain shutdown.

 * The restriction operation needs to be done at a slightly different
   time, necessitating a new hook.

 * Additionally, in the future, we intend to be able to set aside
   a uid range for these qemus to run in, and that involves being
   able to tell qemu to drop privilege by numeric uid and gid.

Thanks to Anthony Perard, Peter Maydell and Ross Lagerwall for
assistance, review and testing.

At least the first patch of this, "xen: link against xentoolcore",
will very likely be necessary, since the corresponding xen.git series
is likely to make Xen 4.10.

Ian.

[PATCH v3 0/8] xen: xen-domid-restrict improvements

[Ian Jackson]

I have been working on trying to get qemu, when running as a Xen
device model, to _actually_ not have power equivalent to root.

I think I have achieved this, with some limitations (which are
discussed in my series against xen.git.

However, there are changes to qemu needed.  In particular

 * The -xen-domid-restrict option does not work properly right now.
   It only restricts a small subset of the descriptors qemu has open.
   I am introducing a new library call in the Xen libraries for this,
   xentoolcore_restrict_all.

 * We need to call a different function on domain shutdown.

 * The restriction operation needs to be done at a slightly different
   time, necessitating a new hook.

 * Additionally, in the future, we intend to be able to set aside
   a uid range for these qemus to run in, and that involves being
   able to tell qemu to drop privilege by numeric uid and gid.

Thanks to Anthony Perard, Peter Maydell and Ross Lagerwall for
assistance, review and testing.

At least the first patch of this, "xen: link against xentoolcore",
will very likely be necessary, since the corresponding xen.git series
is likely to make Xen 4.10.

Ian.

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[Qemu-devel] [PATCH 1/8] xen: link against xentoolcore

[Ian Jackson]

From: Anthony PERARD <anthony.perard@citrix.com>

Xen libraries 4.10 will include a new xentoolcore library, without
which xendevicemodel et al will not work.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 configure | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index fd7e3a5..6f691df 100755
--- a/configure
+++ b/configure
@@ -2072,7 +2072,7 @@ if test "$xen" != "no" ; then
       $($pkg_config --modversion xencontrol | sed 's/\./ /g') )"
     xen=yes
     xen_pc="xencontrol xenstore xenguest xenforeignmemory xengnttab"
-    xen_pc="$xen_pc xenevtchn xendevicemodel"
+    xen_pc="$xen_pc xenevtchn xendevicemodel xentoolcore"
     QEMU_CFLAGS="$QEMU_CFLAGS $($pkg_config --cflags $xen_pc)"
     libs_softmmu="$($pkg_config --libs $xen_pc) $libs_softmmu"
     LDFLAGS="$($pkg_config --libs $xen_pc) $LDFLAGS"
@@ -2104,18 +2104,20 @@ EOF
         cat > $TMPC <<EOF &&
 #undef XC_WANT_COMPAT_MAP_FOREIGN_API
 #include <xenforeignmemory.h>
+#include <xentoolcore.h>
 int main(void) {
   xenforeignmemory_handle *xfmem;
 
   xfmem = xenforeignmemory_open(0, 0);
   xenforeignmemory_map2(xfmem, 0, 0, 0, 0, 0, 0, 0);
+  xentoolcore_restrict_all(0);
 
   return 0;
 }
 EOF
-        compile_prog "" "$xen_libs -lxendevicemodel $xen_stable_libs"
+        compile_prog "" "$xen_libs -lxendevicemodel $xen_stable_libs -lxentoolcore"
       then
-      xen_stable_libs="-lxendevicemodel $xen_stable_libs"
+      xen_stable_libs="-lxendevicemodel $xen_stable_libs -lxentoolcore"
       xen_ctrl_version=41000
       xen=yes
     elif
-- 
2.1.4

[PATCH 1/8] xen: link against xentoolcore

[Ian Jackson]

From: Anthony PERARD <anthony.perard@citrix.com>

Xen libraries 4.10 will include a new xentoolcore library, without
which xendevicemodel et al will not work.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 configure | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index fd7e3a5..6f691df 100755
--- a/configure
+++ b/configure
@@ -2072,7 +2072,7 @@ if test "$xen" != "no" ; then
       $($pkg_config --modversion xencontrol | sed 's/\./ /g') )"
     xen=yes
     xen_pc="xencontrol xenstore xenguest xenforeignmemory xengnttab"
-    xen_pc="$xen_pc xenevtchn xendevicemodel"
+    xen_pc="$xen_pc xenevtchn xendevicemodel xentoolcore"
     QEMU_CFLAGS="$QEMU_CFLAGS $($pkg_config --cflags $xen_pc)"
     libs_softmmu="$($pkg_config --libs $xen_pc) $libs_softmmu"
     LDFLAGS="$($pkg_config --libs $xen_pc) $LDFLAGS"
@@ -2104,18 +2104,20 @@ EOF
         cat > $TMPC <<EOF &&
 #undef XC_WANT_COMPAT_MAP_FOREIGN_API
 #include <xenforeignmemory.h>
+#include <xentoolcore.h>
 int main(void) {
   xenforeignmemory_handle *xfmem;
 
   xfmem = xenforeignmemory_open(0, 0);
   xenforeignmemory_map2(xfmem, 0, 0, 0, 0, 0, 0, 0);
+  xentoolcore_restrict_all(0);
 
   return 0;
 }
 EOF
-        compile_prog "" "$xen_libs -lxendevicemodel $xen_stable_libs"
+        compile_prog "" "$xen_libs -lxendevicemodel $xen_stable_libs -lxentoolcore"
       then
-      xen_stable_libs="-lxendevicemodel $xen_stable_libs"
+      xen_stable_libs="-lxendevicemodel $xen_stable_libs -lxentoolcore"
       xen_ctrl_version=41000
       xen=yes
     elif
-- 
2.1.4


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[Qemu-devel] [PATCH 2/8] xen: restrict: use xentoolcore_restrict_all

[Ian Jackson]

And insist that it works.

Drop individual use of xendevicemodel_restrict and
xenforeignmemory_restrict.  These are not actually effective in this
version of qemu, because qemu has a large number of fds open onto
various Xen control devices.

The restriction arrangements are still not right, because the
restriction needs to be done very late - after qemu has opened all of
its control fds.

xentoolcore_restrict_all and xentoolcore.h are available in Xen 4.10
and later, only.  Provide a compatibility stub.  And drop the
compatibility stubs for the old functions.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Modify the compatibility code, too.
    Bump this patch ahead of "defer call to xen_restrict until running"
    Retain call to xentoolcore_restrict_all

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 include/hw/xen/xen_common.h | 46 +++++++++++----------------------------------
 1 file changed, 11 insertions(+), 35 deletions(-)

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 86c7f26..3f44a63 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -91,6 +91,16 @@ static inline void *xenforeignmemory_map2(xenforeignmemory_handle *h,
     return xenforeignmemory_map(h, dom, prot, pages, arr, err);
 }
 
+static inline int xentoolcore_restrict_all(domid_t domid)
+{
+    errno = ENOTTY;
+    return -1;
+}
+
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 41000 */
+
+#include <xentoolcore.h>
+
 #endif
 
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
@@ -218,20 +228,6 @@ static inline int xendevicemodel_set_mem_type(
     return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
 }
 
-static inline int xendevicemodel_restrict(
-    xendevicemodel_handle *dmod, domid_t domid)
-{
-    errno = ENOTTY;
-    return -1;
-}
-
-static inline int xenforeignmemory_restrict(
-    xenforeignmemory_handle *fmem, domid_t domid)
-{
-    errno = ENOTTY;
-    return -1;
-}
-
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
 
 #undef XC_WANT_COMPAT_DEVICEMODEL_API
@@ -290,28 +286,8 @@ static inline int xen_modified_memory(domid_t domid, uint64_t first_pfn,
 static inline int xen_restrict(domid_t domid)
 {
     int rc;
-
-    /* Attempt to restrict devicemodel operations */
-    rc = xendevicemodel_restrict(xen_dmod, domid);
+    rc = xentoolcore_restrict_all(domid);
     trace_xen_domid_restrict(rc ? errno : 0);
-
-    if (rc < 0) {
-        /*
-         * If errno is ENOTTY then restriction is not implemented so
-         * there's no point in trying to restrict other types of
-         * operation, but it should not be treated as a failure.
-         */
-        if (errno == ENOTTY) {
-            return 0;
-        }
-
-        return rc;
-    }
-
-    /* Restrict foreignmemory operations */
-    rc = xenforeignmemory_restrict(xen_fmem, domid);
-    trace_xen_domid_restrict(rc ? errno : 0);
-
     return rc;
 }
 
-- 
2.1.4

[PATCH 2/8] xen: restrict: use xentoolcore_restrict_all

[Ian Jackson]

And insist that it works.

Drop individual use of xendevicemodel_restrict and
xenforeignmemory_restrict.  These are not actually effective in this
version of qemu, because qemu has a large number of fds open onto
various Xen control devices.

The restriction arrangements are still not right, because the
restriction needs to be done very late - after qemu has opened all of
its control fds.

xentoolcore_restrict_all and xentoolcore.h are available in Xen 4.10
and later, only.  Provide a compatibility stub.  And drop the
compatibility stubs for the old functions.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Modify the compatibility code, too.
    Bump this patch ahead of "defer call to xen_restrict until running"
    Retain call to xentoolcore_restrict_all

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 include/hw/xen/xen_common.h | 46 +++++++++++----------------------------------
 1 file changed, 11 insertions(+), 35 deletions(-)

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 86c7f26..3f44a63 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -91,6 +91,16 @@ static inline void *xenforeignmemory_map2(xenforeignmemory_handle *h,
     return xenforeignmemory_map(h, dom, prot, pages, arr, err);
 }
 
+static inline int xentoolcore_restrict_all(domid_t domid)
+{
+    errno = ENOTTY;
+    return -1;
+}
+
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 41000 */
+
+#include <xentoolcore.h>
+
 #endif
 
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
@@ -218,20 +228,6 @@ static inline int xendevicemodel_set_mem_type(
     return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
 }
 
-static inline int xendevicemodel_restrict(
-    xendevicemodel_handle *dmod, domid_t domid)
-{
-    errno = ENOTTY;
-    return -1;
-}
-
-static inline int xenforeignmemory_restrict(
-    xenforeignmemory_handle *fmem, domid_t domid)
-{
-    errno = ENOTTY;
-    return -1;
-}
-
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
 
 #undef XC_WANT_COMPAT_DEVICEMODEL_API
@@ -290,28 +286,8 @@ static inline int xen_modified_memory(domid_t domid, uint64_t first_pfn,
 static inline int xen_restrict(domid_t domid)
 {
     int rc;
-
-    /* Attempt to restrict devicemodel operations */
-    rc = xendevicemodel_restrict(xen_dmod, domid);
+    rc = xentoolcore_restrict_all(domid);
     trace_xen_domid_restrict(rc ? errno : 0);
-
-    if (rc < 0) {
-        /*
-         * If errno is ENOTTY then restriction is not implemented so
-         * there's no point in trying to restrict other types of
-         * operation, but it should not be treated as a failure.
-         */
-        if (errno == ENOTTY) {
-            return 0;
-        }
-
-        return rc;
-    }
-
-    /* Restrict foreignmemory operations */
-    rc = xenforeignmemory_restrict(xen_fmem, domid);
-    trace_xen_domid_restrict(rc ? errno : 0);
-
     return rc;
 }
 
-- 
2.1.4


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[Qemu-devel] [PATCH 3/8] xen: defer call to xen_restrict until just before os_setup_post

[Ian Jackson]

We need to restrict *all* the control fds that qemu opens.  Looking in
/proc/PID/fd shows there are many; their allocation seems scattered
throughout Xen support code in qemu.

We must postpone the restrict call until roughly the same time as qemu
changes its uid, chroots (if applicable), and so on.

There doesn't seem to be an appropriate hook already.  The RunState
change hook fires at different times depending on exactly what mode
qemu is operating in.

And it appears that no-one but the Xen code wants a hook at this phase
of execution.  So, introduce a bare call to a new function
xen_setup_post, just before os_setup_post.  Also provide the
appropriate stub for when Xen compilation is disabled.

We do the restriction before rather than after os_setup_post, because
xen_restrict may need to open /dev/null, and os_setup_post might have
called chroot.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v3: Do xen_setup_post just before, not just after, os_setup_post,
    to improve interaction with chroot.  Thanks to Ross Lagerwall.
---
 hw/i386/xen/xen-hvm.c   |  8 --------
 hw/xen/xen-common.c     | 13 +++++++++++++
 include/sysemu/sysemu.h |  2 ++
 stubs/xen-hvm.c         |  5 +++++
 vl.c                    |  1 +
 5 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index d9ccd5d..7b60ec6 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1254,14 +1254,6 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
         goto err;
     }
 
-    if (xen_domid_restrict) {
-        rc = xen_restrict(xen_domid);
-        if (rc < 0) {
-            error_report("failed to restrict: error %d", errno);
-            goto err;
-        }
-    }
-
     xen_create_ioreq_server(xen_domid, &state->ioservid);
 
     state->exit.notify = xen_exit_notifier;
diff --git a/hw/xen/xen-common.c b/hw/xen/xen-common.c
index 632a938..4056420 100644
--- a/hw/xen/xen-common.c
+++ b/hw/xen/xen-common.c
@@ -117,6 +117,19 @@ static void xen_change_state_handler(void *opaque, int running,
     }
 }
 
+void xen_setup_post(void)
+{
+    int rc;
+
+    if (xen_domid_restrict) {
+        rc = xen_restrict(xen_domid);
+        if (rc < 0) {
+            perror("xen: failed to restrict");
+            exit(1);
+        }
+    }
+}
+
 static int xen_init(MachineState *ms)
 {
     xen_xc = xc_interface_open(0, 0, 0);
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index b213696..b064a55 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -93,6 +93,8 @@ void qemu_remove_machine_init_done_notifier(Notifier *notify);
 
 void qemu_announce_self(void);
 
+void xen_setup_post(void);
+
 extern int autostart;
 
 typedef enum {
diff --git a/stubs/xen-hvm.c b/stubs/xen-hvm.c
index 3ca6c51..9701feb 100644
--- a/stubs/xen-hvm.c
+++ b/stubs/xen-hvm.c
@@ -13,6 +13,7 @@
 #include "hw/xen/xen.h"
 #include "exec/memory.h"
 #include "qmp-commands.h"
+#include "sysemu/sysemu.h"
 
 int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num)
 {
@@ -61,3 +62,7 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
 void qmp_xen_set_global_dirty_log(bool enable, Error **errp)
 {
 }
+
+void xen_setup_post(void)
+{
+}
diff --git a/vl.c b/vl.c
index fb1f05b..ca06553 100644
--- a/vl.c
+++ b/vl.c
@@ -4792,6 +4792,7 @@ int main(int argc, char **argv, char **envp)
         vm_start();
     }
 
+    xen_setup_post();
     os_setup_post();
 
     main_loop();
-- 
2.1.4

[PATCH 3/8] xen: defer call to xen_restrict until just before os_setup_post

[Ian Jackson]

We need to restrict *all* the control fds that qemu opens.  Looking in
/proc/PID/fd shows there are many; their allocation seems scattered
throughout Xen support code in qemu.

We must postpone the restrict call until roughly the same time as qemu
changes its uid, chroots (if applicable), and so on.

There doesn't seem to be an appropriate hook already.  The RunState
change hook fires at different times depending on exactly what mode
qemu is operating in.

And it appears that no-one but the Xen code wants a hook at this phase
of execution.  So, introduce a bare call to a new function
xen_setup_post, just before os_setup_post.  Also provide the
appropriate stub for when Xen compilation is disabled.

We do the restriction before rather than after os_setup_post, because
xen_restrict may need to open /dev/null, and os_setup_post might have
called chroot.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v3: Do xen_setup_post just before, not just after, os_setup_post,
    to improve interaction with chroot.  Thanks to Ross Lagerwall.
---
 hw/i386/xen/xen-hvm.c   |  8 --------
 hw/xen/xen-common.c     | 13 +++++++++++++
 include/sysemu/sysemu.h |  2 ++
 stubs/xen-hvm.c         |  5 +++++
 vl.c                    |  1 +
 5 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index d9ccd5d..7b60ec6 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1254,14 +1254,6 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
         goto err;
     }
 
-    if (xen_domid_restrict) {
-        rc = xen_restrict(xen_domid);
-        if (rc < 0) {
-            error_report("failed to restrict: error %d", errno);
-            goto err;
-        }
-    }
-
     xen_create_ioreq_server(xen_domid, &state->ioservid);
 
     state->exit.notify = xen_exit_notifier;
diff --git a/hw/xen/xen-common.c b/hw/xen/xen-common.c
index 632a938..4056420 100644
--- a/hw/xen/xen-common.c
+++ b/hw/xen/xen-common.c
@@ -117,6 +117,19 @@ static void xen_change_state_handler(void *opaque, int running,
     }
 }
 
+void xen_setup_post(void)
+{
+    int rc;
+
+    if (xen_domid_restrict) {
+        rc = xen_restrict(xen_domid);
+        if (rc < 0) {
+            perror("xen: failed to restrict");
+            exit(1);
+        }
+    }
+}
+
 static int xen_init(MachineState *ms)
 {
     xen_xc = xc_interface_open(0, 0, 0);
diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
index b213696..b064a55 100644
--- a/include/sysemu/sysemu.h
+++ b/include/sysemu/sysemu.h
@@ -93,6 +93,8 @@ void qemu_remove_machine_init_done_notifier(Notifier *notify);
 
 void qemu_announce_self(void);
 
+void xen_setup_post(void);
+
 extern int autostart;
 
 typedef enum {
diff --git a/stubs/xen-hvm.c b/stubs/xen-hvm.c
index 3ca6c51..9701feb 100644
--- a/stubs/xen-hvm.c
+++ b/stubs/xen-hvm.c
@@ -13,6 +13,7 @@
 #include "hw/xen/xen.h"
 #include "exec/memory.h"
 #include "qmp-commands.h"
+#include "sysemu/sysemu.h"
 
 int xen_pci_slot_get_pirq(PCIDevice *pci_dev, int irq_num)
 {
@@ -61,3 +62,7 @@ void xen_hvm_init(PCMachineState *pcms, MemoryRegion **ram_memory)
 void qmp_xen_set_global_dirty_log(bool enable, Error **errp)
 {
 }
+
+void xen_setup_post(void)
+{
+}
diff --git a/vl.c b/vl.c
index fb1f05b..ca06553 100644
--- a/vl.c
+++ b/vl.c
@@ -4792,6 +4792,7 @@ int main(int argc, char **argv, char **envp)
         vm_start();
     }
 
+    xen_setup_post();
     os_setup_post();
 
     main_loop();
-- 
2.1.4


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[Qemu-devel] [PATCH 4/8] xen: destroy_hvm_domain: Move reason into a variable

[Ian Jackson]

We are going to want to reuse this.

No functional change.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
---
 hw/i386/xen/xen-hvm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index 7b60ec6..83420cd 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1387,12 +1387,13 @@ void destroy_hvm_domain(bool reboot)
     xc_interface *xc_handle;
     int sts;
 
+    unsigned int reason = reboot ? SHUTDOWN_reboot : SHUTDOWN_poweroff;
+
     xc_handle = xc_interface_open(0, 0, 0);
     if (xc_handle == NULL) {
         fprintf(stderr, "Cannot acquire xenctrl handle\n");
     } else {
-        sts = xc_domain_shutdown(xc_handle, xen_domid,
-                                 reboot ? SHUTDOWN_reboot : SHUTDOWN_poweroff);
+        sts = xc_domain_shutdown(xc_handle, xen_domid, reason);
         if (sts != 0) {
             fprintf(stderr, "xc_domain_shutdown failed to issue %s, "
                     "sts %d, %s\n", reboot ? "reboot" : "poweroff",
-- 
2.1.4

[PATCH 4/8] xen: destroy_hvm_domain: Move reason into a variable

[Ian Jackson]

We are going to want to reuse this.

No functional change.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Reviewed-by: Anthony PERARD <anthony.perard@citrix.com>
---
 hw/i386/xen/xen-hvm.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index 7b60ec6..83420cd 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1387,12 +1387,13 @@ void destroy_hvm_domain(bool reboot)
     xc_interface *xc_handle;
     int sts;
 
+    unsigned int reason = reboot ? SHUTDOWN_reboot : SHUTDOWN_poweroff;
+
     xc_handle = xc_interface_open(0, 0, 0);
     if (xc_handle == NULL) {
         fprintf(stderr, "Cannot acquire xenctrl handle\n");
     } else {
-        sts = xc_domain_shutdown(xc_handle, xen_domid,
-                                 reboot ? SHUTDOWN_reboot : SHUTDOWN_poweroff);
+        sts = xc_domain_shutdown(xc_handle, xen_domid, reason);
         if (sts != 0) {
             fprintf(stderr, "xc_domain_shutdown failed to issue %s, "
                     "sts %d, %s\n", reboot ? "reboot" : "poweroff",
-- 
2.1.4


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[Qemu-devel] [PATCH 5/8] xen: move xc_interface compatibility fallback further up the file

[Ian Jackson]

We are going to want to use the dummy xendevicemodel_handle type in
new stub functions in the CONFIG_XEN_CTRL_INTERFACE_VERSION < 41000
section.  So we need to provide that definition, or (as applicable)
include the appropriate header, earlier in the file.

(Ideally the newer compatibility layers would be at the bottom of the
file, so that they can naturally benefit from the compatibility layers
for earlier version.  But that's rather too much for this series.)

No functional change.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: New patch in v2 of the series
---
 include/hw/xen/xen_common.h | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 3f44a63..8efdb8a 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -78,6 +78,17 @@ static inline void *xenforeignmemory_map(xc_interface *h, uint32_t dom,
 
 extern xenforeignmemory_handle *xen_fmem;
 
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
+
+typedef xc_interface xendevicemodel_handle;
+
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
+
+#undef XC_WANT_COMPAT_DEVICEMODEL_API
+#include <xendevicemodel.h>
+
+#endif
+
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 41000
 
 #define XEN_COMPAT_PHYSMAP
@@ -105,8 +116,6 @@ static inline int xentoolcore_restrict_all(domid_t domid)
 
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
 
-typedef xc_interface xendevicemodel_handle;
-
 static inline xendevicemodel_handle *xendevicemodel_open(
     struct xentoollog_logger *logger, unsigned int open_flags)
 {
@@ -228,11 +237,6 @@ static inline int xendevicemodel_set_mem_type(
     return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
 }
 
-#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
-
-#undef XC_WANT_COMPAT_DEVICEMODEL_API
-#include <xendevicemodel.h>
-
 #endif
 
 extern xendevicemodel_handle *xen_dmod;
-- 
2.1.4

[PATCH 5/8] xen: move xc_interface compatibility fallback further up the file

[Ian Jackson]

We are going to want to use the dummy xendevicemodel_handle type in
new stub functions in the CONFIG_XEN_CTRL_INTERFACE_VERSION < 41000
section.  So we need to provide that definition, or (as applicable)
include the appropriate header, earlier in the file.

(Ideally the newer compatibility layers would be at the bottom of the
file, so that they can naturally benefit from the compatibility layers
for earlier version.  But that's rather too much for this series.)

No functional change.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: New patch in v2 of the series
---
 include/hw/xen/xen_common.h | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 3f44a63..8efdb8a 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -78,6 +78,17 @@ static inline void *xenforeignmemory_map(xc_interface *h, uint32_t dom,
 
 extern xenforeignmemory_handle *xen_fmem;
 
+#if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
+
+typedef xc_interface xendevicemodel_handle;
+
+#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
+
+#undef XC_WANT_COMPAT_DEVICEMODEL_API
+#include <xendevicemodel.h>
+
+#endif
+
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 41000
 
 #define XEN_COMPAT_PHYSMAP
@@ -105,8 +116,6 @@ static inline int xentoolcore_restrict_all(domid_t domid)
 
 #if CONFIG_XEN_CTRL_INTERFACE_VERSION < 40900
 
-typedef xc_interface xendevicemodel_handle;
-
 static inline xendevicemodel_handle *xendevicemodel_open(
     struct xentoollog_logger *logger, unsigned int open_flags)
 {
@@ -228,11 +237,6 @@ static inline int xendevicemodel_set_mem_type(
     return xc_hvm_set_mem_type(dmod, domid, mem_type, first_pfn, nr);
 }
 
-#else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 40900 */
-
-#undef XC_WANT_COMPAT_DEVICEMODEL_API
-#include <xendevicemodel.h>
-
 #endif
 
 extern xendevicemodel_handle *xen_dmod;
-- 
2.1.4


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[Qemu-devel] [PATCH 6/8] xen: destroy_hvm_domain: Try xendevicemodel_shutdown

[Ian Jackson]

xc_interface_open etc. is not going to work if we have dropped
privilege, but xendevicemodel_shutdown will if everything is new
enough.

xendevicemodel_shutdown is only availabe in Xen 4.10 and later, so
provide a stub for earlier versions.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Add compatibility stub for Xen < 4.10.
    Fix coding style.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 hw/i386/xen/xen-hvm.c       | 10 ++++++++++
 include/hw/xen/xen_common.h |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index 83420cd..25b8b14 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1386,9 +1386,19 @@ void destroy_hvm_domain(bool reboot)
 {
     xc_interface *xc_handle;
     int sts;
+    int rc;
 
     unsigned int reason = reboot ? SHUTDOWN_reboot : SHUTDOWN_poweroff;
 
+    if (xen_dmod) {
+        rc = xendevicemodel_shutdown(xen_dmod, xen_domid, reason);
+        if (!rc) {
+            return;
+        }
+        perror("xendevicemodel_shutdown failed");
+        /* well, try the old thing then */
+    }
+
     xc_handle = xc_interface_open(0, 0, 0);
     if (xc_handle == NULL) {
         fprintf(stderr, "Cannot acquire xenctrl handle\n");
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 8efdb8a..1d6fb57 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -108,6 +108,13 @@ static inline int xentoolcore_restrict_all(domid_t domid)
     return -1;
 }
 
+static inline int xendevicemodel_shutdown(xendevicemodel_handle *dmod,
+                                          domid_t domid, unsigned int reason)
+{
+    errno = ENOTTY;
+    return -1;
+}
+
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 41000 */
 
 #include <xentoolcore.h>
-- 
2.1.4

[PATCH 6/8] xen: destroy_hvm_domain: Try xendevicemodel_shutdown

[Ian Jackson]

xc_interface_open etc. is not going to work if we have dropped
privilege, but xendevicemodel_shutdown will if everything is new
enough.

xendevicemodel_shutdown is only availabe in Xen 4.10 and later, so
provide a stub for earlier versions.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Add compatibility stub for Xen < 4.10.
    Fix coding style.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 hw/i386/xen/xen-hvm.c       | 10 ++++++++++
 include/hw/xen/xen_common.h |  7 +++++++
 2 files changed, 17 insertions(+)

diff --git a/hw/i386/xen/xen-hvm.c b/hw/i386/xen/xen-hvm.c
index 83420cd..25b8b14 100644
--- a/hw/i386/xen/xen-hvm.c
+++ b/hw/i386/xen/xen-hvm.c
@@ -1386,9 +1386,19 @@ void destroy_hvm_domain(bool reboot)
 {
     xc_interface *xc_handle;
     int sts;
+    int rc;
 
     unsigned int reason = reboot ? SHUTDOWN_reboot : SHUTDOWN_poweroff;
 
+    if (xen_dmod) {
+        rc = xendevicemodel_shutdown(xen_dmod, xen_domid, reason);
+        if (!rc) {
+            return;
+        }
+        perror("xendevicemodel_shutdown failed");
+        /* well, try the old thing then */
+    }
+
     xc_handle = xc_interface_open(0, 0, 0);
     if (xc_handle == NULL) {
         fprintf(stderr, "Cannot acquire xenctrl handle\n");
diff --git a/include/hw/xen/xen_common.h b/include/hw/xen/xen_common.h
index 8efdb8a..1d6fb57 100644
--- a/include/hw/xen/xen_common.h
+++ b/include/hw/xen/xen_common.h
@@ -108,6 +108,13 @@ static inline int xentoolcore_restrict_all(domid_t domid)
     return -1;
 }
 
+static inline int xendevicemodel_shutdown(xendevicemodel_handle *dmod,
+                                          domid_t domid, unsigned int reason)
+{
+    errno = ENOTTY;
+    return -1;
+}
+
 #else /* CONFIG_XEN_CTRL_INTERFACE_VERSION >= 41000 */
 
 #include <xentoolcore.h>
-- 
2.1.4


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[Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

This allows the caller to specify a uid and gid to use, even if there
is no corresponding password entry.  This will be useful in certain
Xen configurations.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v3: Error messages fixed.  Thanks to Peter Maydell and Ross Lagerwall.
v2: Coding style fixes.
---
 os-posix.c      | 49 ++++++++++++++++++++++++++++++++++++++++---------
 qemu-options.hx | 12 ++++++++++++
 2 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/os-posix.c b/os-posix.c
index 92e9d85..6cc5868 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -43,6 +43,8 @@
 #endif
 
 static struct passwd *user_pwd;
+static uid_t user_uid = (uid_t)-1;
+static gid_t user_gid = (gid_t)-1;
 static const char *chroot_dir;
 static int daemonize;
 static int daemon_pipe;
@@ -134,6 +136,9 @@ void os_set_proc_name(const char *s)
  */
 void os_parse_cmd_args(int index, const char *optarg)
 {
+    unsigned long lv;
+    char *ep;
+    int rc;
     switch (index) {
 #ifdef CONFIG_SLIRP
     case QEMU_OPTION_smb:
@@ -150,6 +155,22 @@ void os_parse_cmd_args(int index, const char *optarg)
             exit(1);
         }
         break;
+    case QEMU_OPTION_runasid:
+        errno = 0;
+        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
+        user_uid = lv; /* overflow here is ID in C99 */
+        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
+            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
+            exit(1);
+        }
+        lv = 0;
+        rc = qemu_strtoul(ep + 1, 0, 0, &lv);
+        user_gid = lv; /* overflow here is ID in C99 */
+        if (rc || user_gid != lv || user_gid == (gid_t)-1) {
+            fprintf(stderr, "Could not obtain gid from \"%s\"", optarg);
+            exit(1);
+        }
+        break;
     case QEMU_OPTION_chroot:
         chroot_dir = optarg;
         break;
@@ -166,18 +187,28 @@ void os_parse_cmd_args(int index, const char *optarg)
 
 static void change_process_uid(void)
 {
-    if (user_pwd) {
-        if (setgid(user_pwd->pw_gid) < 0) {
-            fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
+    if (user_pwd || user_uid != (uid_t)-1) {
+        gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
+        uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
+        if (setgid(intended_gid) < 0) {
+            fprintf(stderr, "Failed to setgid(%d)\n", intended_gid);
             exit(1);
         }
-        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
-            fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
-                    user_pwd->pw_name, user_pwd->pw_gid);
-            exit(1);
+        if (user_pwd) {
+            if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
+                fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
+                        user_pwd->pw_name, user_pwd->pw_gid);
+                exit(1);
+            }
+        } else {
+            if (setgroups(1, &user_gid) < 0) {
+                fprintf(stderr, "Failed to setgroups(1, [%d])",
+                        user_gid);
+                exit(1);
+            }
         }
-        if (setuid(user_pwd->pw_uid) < 0) {
-            fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
+        if (setuid(intended_uid) < 0) {
+            fprintf(stderr, "Failed to setuid(%d)\n", intended_uid);
             exit(1);
         }
         if (setuid(0) != -1) {
diff --git a/qemu-options.hx b/qemu-options.hx
index 9f6e2ad..34a5329 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
 to the specified user.
 ETEXI
 
+#ifndef _WIN32
+DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
+    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
+    QEMU_ARCH_ALL)
+#endif
+STEXI
+@item -runasid @var{uid}.@var{gid}
+@findex -runasid
+Immediately before starting guest execution, drop root privileges, switching
+to the specified uid and gid.
+ETEXI
+
 DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
     "-prom-env variable=value\n"
     "                set OpenBIOS nvram variables\n",
-- 
2.1.4

[PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

This allows the caller to specify a uid and gid to use, even if there
is no corresponding password entry.  This will be useful in certain
Xen configurations.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v3: Error messages fixed.  Thanks to Peter Maydell and Ross Lagerwall.
v2: Coding style fixes.
---
 os-posix.c      | 49 ++++++++++++++++++++++++++++++++++++++++---------
 qemu-options.hx | 12 ++++++++++++
 2 files changed, 52 insertions(+), 9 deletions(-)

diff --git a/os-posix.c b/os-posix.c
index 92e9d85..6cc5868 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -43,6 +43,8 @@
 #endif
 
 static struct passwd *user_pwd;
+static uid_t user_uid = (uid_t)-1;
+static gid_t user_gid = (gid_t)-1;
 static const char *chroot_dir;
 static int daemonize;
 static int daemon_pipe;
@@ -134,6 +136,9 @@ void os_set_proc_name(const char *s)
  */
 void os_parse_cmd_args(int index, const char *optarg)
 {
+    unsigned long lv;
+    char *ep;
+    int rc;
     switch (index) {
 #ifdef CONFIG_SLIRP
     case QEMU_OPTION_smb:
@@ -150,6 +155,22 @@ void os_parse_cmd_args(int index, const char *optarg)
             exit(1);
         }
         break;
+    case QEMU_OPTION_runasid:
+        errno = 0;
+        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
+        user_uid = lv; /* overflow here is ID in C99 */
+        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
+            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
+            exit(1);
+        }
+        lv = 0;
+        rc = qemu_strtoul(ep + 1, 0, 0, &lv);
+        user_gid = lv; /* overflow here is ID in C99 */
+        if (rc || user_gid != lv || user_gid == (gid_t)-1) {
+            fprintf(stderr, "Could not obtain gid from \"%s\"", optarg);
+            exit(1);
+        }
+        break;
     case QEMU_OPTION_chroot:
         chroot_dir = optarg;
         break;
@@ -166,18 +187,28 @@ void os_parse_cmd_args(int index, const char *optarg)
 
 static void change_process_uid(void)
 {
-    if (user_pwd) {
-        if (setgid(user_pwd->pw_gid) < 0) {
-            fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
+    if (user_pwd || user_uid != (uid_t)-1) {
+        gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
+        uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
+        if (setgid(intended_gid) < 0) {
+            fprintf(stderr, "Failed to setgid(%d)\n", intended_gid);
             exit(1);
         }
-        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
-            fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
-                    user_pwd->pw_name, user_pwd->pw_gid);
-            exit(1);
+        if (user_pwd) {
+            if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
+                fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
+                        user_pwd->pw_name, user_pwd->pw_gid);
+                exit(1);
+            }
+        } else {
+            if (setgroups(1, &user_gid) < 0) {
+                fprintf(stderr, "Failed to setgroups(1, [%d])",
+                        user_gid);
+                exit(1);
+            }
         }
-        if (setuid(user_pwd->pw_uid) < 0) {
-            fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
+        if (setuid(intended_uid) < 0) {
+            fprintf(stderr, "Failed to setuid(%d)\n", intended_uid);
             exit(1);
         }
         if (setuid(0) != -1) {
diff --git a/qemu-options.hx b/qemu-options.hx
index 9f6e2ad..34a5329 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
 to the specified user.
 ETEXI
 
+#ifndef _WIN32
+DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
+    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
+    QEMU_ARCH_ALL)
+#endif
+STEXI
+@item -runasid @var{uid}.@var{gid}
+@findex -runasid
+Immediately before starting guest execution, drop root privileges, switching
+to the specified uid and gid.
+ETEXI
+
 DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
     "-prom-env variable=value\n"
     "                set OpenBIOS nvram variables\n",
-- 
2.1.4


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[Qemu-devel] [PATCH 8/8] RFC configure: do_compiler: Dump some extra info under bash

[Ian Jackson]

This makes it much easier to find a particular thing in config.log.

The information may be lacking in other shells, resulting in harmless
empty output.  (This is why we don't use the proper ${FUNCNAME[*]}
array syntax - other shells will choke on that.)

The extra output is only printed if configure is run with bash.  The
something), it is necessary to say   bash ./configure  to get the extra
debug info in the log.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 configure | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure b/configure
index 6f691df..21a2b15 100755
--- a/configure
+++ b/configure
@@ -60,6 +60,10 @@ do_compiler() {
     # is compiler binary to execute.
     local compiler="$1"
     shift
+    echo >>config.log "
+funcs: ${FUNCNAME}
+lines: ${BASH_LINENO}
+files: ${BASH_SOURCE}"
     echo $compiler "$@" >> config.log
     $compiler "$@" >> config.log 2>&1 || return $?
     # Test passed. If this is an --enable-werror build, rerun
-- 
2.1.4

[PATCH 8/8] RFC configure: do_compiler: Dump some extra info under bash

[Ian Jackson]

This makes it much easier to find a particular thing in config.log.

The information may be lacking in other shells, resulting in harmless
empty output.  (This is why we don't use the proper ${FUNCNAME[*]}
array syntax - other shells will choke on that.)

The extra output is only printed if configure is run with bash.  The
something), it is necessary to say   bash ./configure  to get the extra
debug info in the log.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 configure | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure b/configure
index 6f691df..21a2b15 100755
--- a/configure
+++ b/configure
@@ -60,6 +60,10 @@ do_compiler() {
     # is compiler binary to execute.
     local compiler="$1"
     shift
+    echo >>config.log "
+funcs: ${FUNCNAME}
+lines: ${BASH_LINENO}
+files: ${BASH_SOURCE}"
     echo $compiler "$@" >> config.log
     $compiler "$@" >> config.log 2>&1 || return $?
     # Test passed. If this is an --enable-werror build, rerun
-- 
2.1.4


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Re: [Qemu-devel] [PATCH v3 0/8] xen: xen-domid-restrict improvements

[no-reply]

Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 1507314444-30835-1-git-send-email-ian.jackson@eu.citrix.com
Subject: [Qemu-devel] [PATCH v3 0/8] xen: xen-domid-restrict improvements

=== TEST SCRIPT BEGIN ===
#!/bin/bash

BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0

git config --local diff.renamelimit 0
git config --local diff.renames True

commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
    echo "Checking PATCH $n/$total: $(git log -n 1 --format=%s $c)..."
    if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
        failed=1
        echo
    fi
    n=$((n+1))
done

exit $failed
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
f117f53b9e RFC configure: do_compiler: Dump some extra info under bash
8c5c05599f os-posix: Provide new -runasid option
0177ba688d xen: destroy_hvm_domain: Try xendevicemodel_shutdown
2db1c89877 xen: move xc_interface compatibility fallback further up the file
da64bd6104 xen: destroy_hvm_domain: Move reason into a variable
78f35acc0a xen: defer call to xen_restrict until just before os_setup_post
33b46e08dd xen: restrict: use xentoolcore_restrict_all
0eeb4323ab xen: link against xentoolcore

=== OUTPUT BEGIN ===
Checking PATCH 1/8: xen: link against xentoolcore...
Checking PATCH 2/8: xen: restrict: use xentoolcore_restrict_all...
Checking PATCH 3/8: xen: defer call to xen_restrict until just before os_setup_post...
Checking PATCH 4/8: xen: destroy_hvm_domain: Move reason into a variable...
Checking PATCH 5/8: xen: move xc_interface compatibility fallback further up the file...
Checking PATCH 6/8: xen: destroy_hvm_domain: Try xendevicemodel_shutdown...
Checking PATCH 7/8: os-posix: Provide new -runasid option...
ERROR: consider using qemu_strtoul in preference to strtoul
#42: FILE: os-posix.c:160:
+        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */

total: 1 errors, 0 warnings, 94 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

Checking PATCH 8/8: RFC configure: do_compiler: Dump some extra info under bash...
=== OUTPUT END ===

Test command exited with code: 1


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Please send your feedback to patchew-devel@freelists.org

Re: [Qemu-devel] [PATCH v3 0/8] xen: xen-domid-restrict improvements

[no-reply]

Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 1507314444-30835-1-git-send-email-ian.jackson@eu.citrix.com
Subject: [Qemu-devel] [PATCH v3 0/8] xen: xen-domid-restrict improvements

=== TEST SCRIPT BEGIN ===
#!/bin/bash

BASE=base
n=1
total=$(git log --oneline $BASE.. | wc -l)
failed=0

git config --local diff.renamelimit 0
git config --local diff.renames True

commits="$(git log --format=%H --reverse $BASE..)"
for c in $commits; do
    echo "Checking PATCH $n/$total: $(git log -n 1 --format=%s $c)..."
    if ! git show $c --format=email | ./scripts/checkpatch.pl --mailback -; then
        failed=1
        echo
    fi
    n=$((n+1))
done

exit $failed
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
Switched to a new branch 'test'
f117f53b9e RFC configure: do_compiler: Dump some extra info under bash
8c5c05599f os-posix: Provide new -runasid option
0177ba688d xen: destroy_hvm_domain: Try xendevicemodel_shutdown
2db1c89877 xen: move xc_interface compatibility fallback further up the file
da64bd6104 xen: destroy_hvm_domain: Move reason into a variable
78f35acc0a xen: defer call to xen_restrict until just before os_setup_post
33b46e08dd xen: restrict: use xentoolcore_restrict_all
0eeb4323ab xen: link against xentoolcore

=== OUTPUT BEGIN ===
Checking PATCH 1/8: xen: link against xentoolcore...
Checking PATCH 2/8: xen: restrict: use xentoolcore_restrict_all...
Checking PATCH 3/8: xen: defer call to xen_restrict until just before os_setup_post...
Checking PATCH 4/8: xen: destroy_hvm_domain: Move reason into a variable...
Checking PATCH 5/8: xen: move xc_interface compatibility fallback further up the file...
Checking PATCH 6/8: xen: destroy_hvm_domain: Try xendevicemodel_shutdown...
Checking PATCH 7/8: os-posix: Provide new -runasid option...
ERROR: consider using qemu_strtoul in preference to strtoul
#42: FILE: os-posix.c:160:
+        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */

total: 1 errors, 0 warnings, 94 lines checked

Your patch has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

Checking PATCH 8/8: RFC configure: do_compiler: Dump some extra info under bash...
=== OUTPUT END ===

Test command exited with code: 1


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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Sorry for the slooooow response.

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> ---
> v3: Error messages fixed.  Thanks to Peter Maydell and Ross Lagerwall.
> v2: Coding style fixes.
> ---
>  os-posix.c      | 49 ++++++++++++++++++++++++++++++++++++++++---------
>  qemu-options.hx | 12 ++++++++++++
>  2 files changed, 52 insertions(+), 9 deletions(-)
>
> diff --git a/os-posix.c b/os-posix.c
> index 92e9d85..6cc5868 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -43,6 +43,8 @@
>  #endif
>  
>  static struct passwd *user_pwd;
> +static uid_t user_uid = (uid_t)-1;
> +static gid_t user_gid = (gid_t)-1;
>  static const char *chroot_dir;
>  static int daemonize;
>  static int daemon_pipe;
> @@ -134,6 +136,9 @@ void os_set_proc_name(const char *s)
>   */
>  void os_parse_cmd_args(int index, const char *optarg)
>  {
> +    unsigned long lv;
> +    char *ep;
> +    int rc;
>      switch (index) {
>  #ifdef CONFIG_SLIRP
>      case QEMU_OPTION_smb:
> @@ -150,6 +155,22 @@ void os_parse_cmd_args(int index, const char *optarg)
>              exit(1);
>          }
>          break;
> +    case QEMU_OPTION_runasid:
> +        errno = 0;
> +        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */

I'm afraid I can't see why qemu_strtoul() wouldn't work here.  Can you
enlighten me?

> +        user_uid = lv; /* overflow here is ID in C99 */

I don't get the comment.  You check for overflow the obvious way below.
Sure you need a comment?

> +        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
> +            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
> +            exit(1);
> +        }
> +        lv = 0;
> +        rc = qemu_strtoul(ep + 1, 0, 0, &lv);
> +        user_gid = lv; /* overflow here is ID in C99 */

Likewise.

> +        if (rc || user_gid != lv || user_gid == (gid_t)-1) {
> +            fprintf(stderr, "Could not obtain gid from \"%s\"", optarg);
> +            exit(1);
> +        }
> +        break;
>      case QEMU_OPTION_chroot:
>          chroot_dir = optarg;
>          break;
> @@ -166,18 +187,28 @@ void os_parse_cmd_args(int index, const char *optarg)
>  
>  static void change_process_uid(void)
>  {
> -    if (user_pwd) {
> -        if (setgid(user_pwd->pw_gid) < 0) {
> -            fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> +    if (user_pwd || user_uid != (uid_t)-1) {
> +        gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
> +        uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
> +        if (setgid(intended_gid) < 0) {
> +            fprintf(stderr, "Failed to setgid(%d)\n", intended_gid);
>              exit(1);
>          }
> -        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> -            fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
> -                    user_pwd->pw_name, user_pwd->pw_gid);
> -            exit(1);
> +        if (user_pwd) {
> +            if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> +                fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
> +                        user_pwd->pw_name, user_pwd->pw_gid);
> +                exit(1);
> +            }
> +        } else {
> +            if (setgroups(1, &user_gid) < 0) {
> +                fprintf(stderr, "Failed to setgroups(1, [%d])",
> +                        user_gid);
> +                exit(1);
> +            }
>          }
> -        if (setuid(user_pwd->pw_uid) < 0) {
> -            fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
> +        if (setuid(intended_uid) < 0) {
> +            fprintf(stderr, "Failed to setuid(%d)\n", intended_uid);
>              exit(1);
>          }
>          if (setuid(0) != -1) {
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9f6e2ad..34a5329 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
>  to the specified user.
>  ETEXI
>  
> +#ifndef _WIN32
> +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
> +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
> +    QEMU_ARCH_ALL)
> +#endif
> +STEXI
> +@item -runasid @var{uid}.@var{gid}

Didn't we agree on using ':' instead of '.' as separator?

Sure we need yet another option?  Why can't we compatibly extend -runas?

If we truly need both, the rationale belongs into the commit message,
and we need to consider how they interact.  I'd recommend left-to-right
semantics, i.e. if you specify both, the last one wins.  Not what your
current code does, if I read it correctly.

> +@findex -runasid
> +Immediately before starting guest execution, drop root privileges, switching
> +to the specified uid and gid.
> +ETEXI
> +
>  DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
>      "-prom-env variable=value\n"
>      "                set OpenBIOS nvram variables\n",

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Sorry for the slooooow response.

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> ---
> v3: Error messages fixed.  Thanks to Peter Maydell and Ross Lagerwall.
> v2: Coding style fixes.
> ---
>  os-posix.c      | 49 ++++++++++++++++++++++++++++++++++++++++---------
>  qemu-options.hx | 12 ++++++++++++
>  2 files changed, 52 insertions(+), 9 deletions(-)
>
> diff --git a/os-posix.c b/os-posix.c
> index 92e9d85..6cc5868 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -43,6 +43,8 @@
>  #endif
>  
>  static struct passwd *user_pwd;
> +static uid_t user_uid = (uid_t)-1;
> +static gid_t user_gid = (gid_t)-1;
>  static const char *chroot_dir;
>  static int daemonize;
>  static int daemon_pipe;
> @@ -134,6 +136,9 @@ void os_set_proc_name(const char *s)
>   */
>  void os_parse_cmd_args(int index, const char *optarg)
>  {
> +    unsigned long lv;
> +    char *ep;
> +    int rc;
>      switch (index) {
>  #ifdef CONFIG_SLIRP
>      case QEMU_OPTION_smb:
> @@ -150,6 +155,22 @@ void os_parse_cmd_args(int index, const char *optarg)
>              exit(1);
>          }
>          break;
> +    case QEMU_OPTION_runasid:
> +        errno = 0;
> +        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */

I'm afraid I can't see why qemu_strtoul() wouldn't work here.  Can you
enlighten me?

> +        user_uid = lv; /* overflow here is ID in C99 */

I don't get the comment.  You check for overflow the obvious way below.
Sure you need a comment?

> +        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
> +            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
> +            exit(1);
> +        }
> +        lv = 0;
> +        rc = qemu_strtoul(ep + 1, 0, 0, &lv);
> +        user_gid = lv; /* overflow here is ID in C99 */

Likewise.

> +        if (rc || user_gid != lv || user_gid == (gid_t)-1) {
> +            fprintf(stderr, "Could not obtain gid from \"%s\"", optarg);
> +            exit(1);
> +        }
> +        break;
>      case QEMU_OPTION_chroot:
>          chroot_dir = optarg;
>          break;
> @@ -166,18 +187,28 @@ void os_parse_cmd_args(int index, const char *optarg)
>  
>  static void change_process_uid(void)
>  {
> -    if (user_pwd) {
> -        if (setgid(user_pwd->pw_gid) < 0) {
> -            fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> +    if (user_pwd || user_uid != (uid_t)-1) {
> +        gid_t intended_gid = user_pwd ? user_pwd->pw_gid : user_gid;
> +        uid_t intended_uid = user_pwd ? user_pwd->pw_uid : user_uid;
> +        if (setgid(intended_gid) < 0) {
> +            fprintf(stderr, "Failed to setgid(%d)\n", intended_gid);
>              exit(1);
>          }
> -        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> -            fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
> -                    user_pwd->pw_name, user_pwd->pw_gid);
> -            exit(1);
> +        if (user_pwd) {
> +            if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> +                fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
> +                        user_pwd->pw_name, user_pwd->pw_gid);
> +                exit(1);
> +            }
> +        } else {
> +            if (setgroups(1, &user_gid) < 0) {
> +                fprintf(stderr, "Failed to setgroups(1, [%d])",
> +                        user_gid);
> +                exit(1);
> +            }
>          }
> -        if (setuid(user_pwd->pw_uid) < 0) {
> -            fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
> +        if (setuid(intended_uid) < 0) {
> +            fprintf(stderr, "Failed to setuid(%d)\n", intended_uid);
>              exit(1);
>          }
>          if (setuid(0) != -1) {
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9f6e2ad..34a5329 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
>  to the specified user.
>  ETEXI
>  
> +#ifndef _WIN32
> +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
> +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
> +    QEMU_ARCH_ALL)
> +#endif
> +STEXI
> +@item -runasid @var{uid}.@var{gid}

Didn't we agree on using ':' instead of '.' as separator?

Sure we need yet another option?  Why can't we compatibly extend -runas?

If we truly need both, the rationale belongs into the commit message,
and we need to consider how they interact.  I'd recommend left-to-right
semantics, i.e. if you specify both, the last one wins.  Not what your
current code does, if I read it correctly.

> +@findex -runasid
> +Immediately before starting guest execution, drop root privileges, switching
> +to the specified uid and gid.
> +ETEXI
> +
>  DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
>      "-prom-env variable=value\n"
>      "                set OpenBIOS nvram variables\n",

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Hi.  Thanks for the (re)-review.

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Ian Jackson <ian.jackson@eu.citrix.com> writes:
> > +    case QEMU_OPTION_runasid:
> > +        errno = 0;
> > +        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
> 
> I'm afraid I can't see why qemu_strtoul() wouldn't work here.  Can you
> enlighten me?

qemu_strtoul fails (returns an error) if the delimiter (that is, the
first character which is not processed as digit by strtoul) is not
'\0'.  Normally this is desirable, because it correctly rejects
strings like "123blather".  But here we are trying to process a string
whose first non-digit is ':', and we will handle the tail part
explicitly.

It would be possible to use strchr and then to write a '\0' over the
':' but I dislike that processing style (and it is forbidden by the
const annotations on os_parse_cmd_args etc.)

> > +        user_uid = lv; /* overflow here is ID in C99 */
> 
> I don't get the comment.  You check for overflow the obvious way below.
> Sure you need a comment?

This relates to overflow in the assignment, only.  lv is an unsigned
long and user_uid is a uid_t (which may be smaller).  Normally, signed
integer overflow is UB, but this is not the case when converting from
another integer type.

There are two possible overflows: 1. a string that strtoul cannot get
to fit in an unsigned long, which produces a nonzero errno; and, 2. a
value which fits in an unsigned long but not a uid_t.  In the latter
case, we convert it _back_ into an unsigned long, as an implicit
conversion in this middle test:

> > +        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {

If that succeeds, we know we can round-trip it so it is valid.  The
remaining check needed is that it doesn't round trip to the sentinel
uid value.

Does that all make sense ?  I'm not sure how much of this to document
in comments.  It's deeply annoying that C is such a puzzle language
here and that therefore such complicated reasoning and
not-immediately-obvious code is needed, to do something so simple.

If you would like me to remove the comment, I can drop it, of course.
I don't really mind.

> > +#ifndef _WIN32
> > +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
> > +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
> > +    QEMU_ARCH_ALL)
> > +#endif
> > +STEXI
> > +@item -runasid @var{uid}.@var{gid}
> 
> Didn't we agree on using ':' instead of '.' as separator?
> 
> Sure we need yet another option?  Why can't we compatibly extend -runas?

For some reason you are looking at an old version of the patch.  That
may be my fault - there were a few mis-posts.  Sorry about that.

The final version does indeed have ':' and does reuse the -runas
option.

> If we truly need both, the rationale belongs into the commit message,
> and we need to consider how they interact.  I'd recommend left-to-right
> semantics, i.e. if you specify both, the last one wins.  Not what your
> current code does, if I read it correctly.

Happily this is now irrelevant.

I will repost this series after I hear from you about strtoul and the
overflow comment.

Regards,
Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Hi.  Thanks for the (re)-review.

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Ian Jackson <ian.jackson@eu.citrix.com> writes:
> > +    case QEMU_OPTION_runasid:
> > +        errno = 0;
> > +        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
> 
> I'm afraid I can't see why qemu_strtoul() wouldn't work here.  Can you
> enlighten me?

qemu_strtoul fails (returns an error) if the delimiter (that is, the
first character which is not processed as digit by strtoul) is not
'\0'.  Normally this is desirable, because it correctly rejects
strings like "123blather".  But here we are trying to process a string
whose first non-digit is ':', and we will handle the tail part
explicitly.

It would be possible to use strchr and then to write a '\0' over the
':' but I dislike that processing style (and it is forbidden by the
const annotations on os_parse_cmd_args etc.)

> > +        user_uid = lv; /* overflow here is ID in C99 */
> 
> I don't get the comment.  You check for overflow the obvious way below.
> Sure you need a comment?

This relates to overflow in the assignment, only.  lv is an unsigned
long and user_uid is a uid_t (which may be smaller).  Normally, signed
integer overflow is UB, but this is not the case when converting from
another integer type.

There are two possible overflows: 1. a string that strtoul cannot get
to fit in an unsigned long, which produces a nonzero errno; and, 2. a
value which fits in an unsigned long but not a uid_t.  In the latter
case, we convert it _back_ into an unsigned long, as an implicit
conversion in this middle test:

> > +        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {

If that succeeds, we know we can round-trip it so it is valid.  The
remaining check needed is that it doesn't round trip to the sentinel
uid value.

Does that all make sense ?  I'm not sure how much of this to document
in comments.  It's deeply annoying that C is such a puzzle language
here and that therefore such complicated reasoning and
not-immediately-obvious code is needed, to do something so simple.

If you would like me to remove the comment, I can drop it, of course.
I don't really mind.

> > +#ifndef _WIN32
> > +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
> > +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
> > +    QEMU_ARCH_ALL)
> > +#endif
> > +STEXI
> > +@item -runasid @var{uid}.@var{gid}
> 
> Didn't we agree on using ':' instead of '.' as separator?
> 
> Sure we need yet another option?  Why can't we compatibly extend -runas?

For some reason you are looking at an old version of the patch.  That
may be my fault - there were a few mis-posts.  Sorry about that.

The final version does indeed have ':' and does reuse the -runas
option.

> If we truly need both, the rationale belongs into the commit message,
> and we need to consider how they interact.  I'd recommend left-to-right
> semantics, i.e. if you specify both, the last one wins.  Not what your
> current code does, if I read it correctly.

Happily this is now irrelevant.

I will repost this series after I hear from you about strtoul and the
overflow comment.

Regards,
Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> Hi.  Thanks for the (re)-review.
>
> Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
>> Ian Jackson <ian.jackson@eu.citrix.com> writes:
>> > +    case QEMU_OPTION_runasid:
>> > +        errno = 0;
>> > +        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
>> 
>> I'm afraid I can't see why qemu_strtoul() wouldn't work here.  Can you
>> enlighten me?
>
> qemu_strtoul fails (returns an error) if the delimiter (that is, the
> first character which is not processed as digit by strtoul) is not
> '\0'.

It does that *only* when its @endptr argument is null.  Since you pass
&ep, it should work fine here.

>        Normally this is desirable, because it correctly rejects
> strings like "123blather".  But here we are trying to process a string
> whose first non-digit is ':', and we will handle the tail part
> explicitly.
>
> It would be possible to use strchr and then to write a '\0' over the
> ':' but I dislike that processing style (and it is forbidden by the
> const annotations on os_parse_cmd_args etc.)

I'd dislike that, too.

>> > +        user_uid = lv; /* overflow here is ID in C99 */
>> 
>> I don't get the comment.  You check for overflow the obvious way below.
>> Sure you need a comment?
>
> This relates to overflow in the assignment, only.  lv is an unsigned
> long and user_uid is a uid_t (which may be smaller).  Normally, signed
> integer overflow is UB, but this is not the case when converting from
> another integer type.
>
> There are two possible overflows: 1. a string that strtoul cannot get
> to fit in an unsigned long, which produces a nonzero errno; and, 2. a
> value which fits in an unsigned long but not a uid_t.  In the latter
> case, we convert it _back_ into an unsigned long, as an implicit
> conversion in this middle test:
>
>> > +        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
>
> If that succeeds, we know we can round-trip it so it is valid.  The
> remaining check needed is that it doesn't round trip to the sentinel
> uid value.
>
> Does that all make sense ?

Your code makes sense to me.  It's just the comment that confuses me.
Does ID mean "implementation-defined behavior"?  That would be wrong:

       6.3.1.3  Signed and unsigned integers

       [#1] When a value with integer type is converted to  another
       integer   type  other  than  _Bool,  if  the  value  can  be
       represented by the new type, it is unchanged.

       [#2] Otherwise, if the new type is unsigned,  the  value  is
       converted  by repeatedly adding or subtracting one more than
       the maximum value that can be represented in  the  new  type
       until the value is in the range of the new type.

>                             I'm not sure how much of this to document
> in comments.  It's deeply annoying that C is such a puzzle language
> here and that therefore such complicated reasoning and
> not-immediately-obvious code is needed, to do something so simple.
>
> If you would like me to remove the comment, I can drop it, of course.
> I don't really mind.

I'd drop it.

You might find this variation of your code slightly more obvious, or
slightly less:

        if (errno || *ep != '.' || (uid_t)lv != lv || user_uid == (uid_t)-1) {
            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
            exit(1);
        }
        user_uid = lv;

Your choice.

One more thing: please report errors with error_report().  Here:

            error_report("Could not obtain uid");

No need to quote optarg back at the user, because error_report() already
does.

>> > +#ifndef _WIN32
>> > +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
>> > +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
>> > +    QEMU_ARCH_ALL)
>> > +#endif
>> > +STEXI
>> > +@item -runasid @var{uid}.@var{gid}
>> 
>> Didn't we agree on using ':' instead of '.' as separator?
>> 
>> Sure we need yet another option?  Why can't we compatibly extend -runas?
>
> For some reason you are looking at an old version of the patch.  That
> may be my fault - there were a few mis-posts.  Sorry about that.

It could be just as well my fault: my inbox spun out of control before
KVM Forum.

> The final version does indeed have ':' and does reuse the -runas
> option.
>
>> If we truly need both, the rationale belongs into the commit message,
>> and we need to consider how they interact.  I'd recommend left-to-right
>> semantics, i.e. if you specify both, the last one wins.  Not what your
>> current code does, if I read it correctly.
>
> Happily this is now irrelevant.
>
> I will repost this series after I hear from you about strtoul and the
> overflow comment.

Thanks!

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> Hi.  Thanks for the (re)-review.
>
> Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
>> Ian Jackson <ian.jackson@eu.citrix.com> writes:
>> > +    case QEMU_OPTION_runasid:
>> > +        errno = 0;
>> > +        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
>> 
>> I'm afraid I can't see why qemu_strtoul() wouldn't work here.  Can you
>> enlighten me?
>
> qemu_strtoul fails (returns an error) if the delimiter (that is, the
> first character which is not processed as digit by strtoul) is not
> '\0'.

It does that *only* when its @endptr argument is null.  Since you pass
&ep, it should work fine here.

>        Normally this is desirable, because it correctly rejects
> strings like "123blather".  But here we are trying to process a string
> whose first non-digit is ':', and we will handle the tail part
> explicitly.
>
> It would be possible to use strchr and then to write a '\0' over the
> ':' but I dislike that processing style (and it is forbidden by the
> const annotations on os_parse_cmd_args etc.)

I'd dislike that, too.

>> > +        user_uid = lv; /* overflow here is ID in C99 */
>> 
>> I don't get the comment.  You check for overflow the obvious way below.
>> Sure you need a comment?
>
> This relates to overflow in the assignment, only.  lv is an unsigned
> long and user_uid is a uid_t (which may be smaller).  Normally, signed
> integer overflow is UB, but this is not the case when converting from
> another integer type.
>
> There are two possible overflows: 1. a string that strtoul cannot get
> to fit in an unsigned long, which produces a nonzero errno; and, 2. a
> value which fits in an unsigned long but not a uid_t.  In the latter
> case, we convert it _back_ into an unsigned long, as an implicit
> conversion in this middle test:
>
>> > +        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
>
> If that succeeds, we know we can round-trip it so it is valid.  The
> remaining check needed is that it doesn't round trip to the sentinel
> uid value.
>
> Does that all make sense ?

Your code makes sense to me.  It's just the comment that confuses me.
Does ID mean "implementation-defined behavior"?  That would be wrong:

       6.3.1.3  Signed and unsigned integers

       [#1] When a value with integer type is converted to  another
       integer   type  other  than  _Bool,  if  the  value  can  be
       represented by the new type, it is unchanged.

       [#2] Otherwise, if the new type is unsigned,  the  value  is
       converted  by repeatedly adding or subtracting one more than
       the maximum value that can be represented in  the  new  type
       until the value is in the range of the new type.

>                             I'm not sure how much of this to document
> in comments.  It's deeply annoying that C is such a puzzle language
> here and that therefore such complicated reasoning and
> not-immediately-obvious code is needed, to do something so simple.
>
> If you would like me to remove the comment, I can drop it, of course.
> I don't really mind.

I'd drop it.

You might find this variation of your code slightly more obvious, or
slightly less:

        if (errno || *ep != '.' || (uid_t)lv != lv || user_uid == (uid_t)-1) {
            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
            exit(1);
        }
        user_uid = lv;

Your choice.

One more thing: please report errors with error_report().  Here:

            error_report("Could not obtain uid");

No need to quote optarg back at the user, because error_report() already
does.

>> > +#ifndef _WIN32
>> > +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
>> > +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
>> > +    QEMU_ARCH_ALL)
>> > +#endif
>> > +STEXI
>> > +@item -runasid @var{uid}.@var{gid}
>> 
>> Didn't we agree on using ':' instead of '.' as separator?
>> 
>> Sure we need yet another option?  Why can't we compatibly extend -runas?
>
> For some reason you are looking at an old version of the patch.  That
> may be my fault - there were a few mis-posts.  Sorry about that.

It could be just as well my fault: my inbox spun out of control before
KVM Forum.

> The final version does indeed have ':' and does reuse the -runas
> option.
>
>> If we truly need both, the rationale belongs into the commit message,
>> and we need to consider how they interact.  I'd recommend left-to-right
>> semantics, i.e. if you specify both, the last one wins.  Not what your
>> current code does, if I read it correctly.
>
> Happily this is now irrelevant.
>
> I will repost this series after I hear from you about strtoul and the
> overflow comment.

Thanks!

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Ian Jackson <ian.jackson@eu.citrix.com> writes:
> > qemu_strtoul fails (returns an error) if the delimiter (that is, the
> > first character which is not processed as digit by strtoul) is not
> > '\0'.
> 
> It does that *only* when its @endptr argument is null.  Since you pass
> &ep, it should work fine here.

I have just read it again and you are right.  Sorry.  I will fix this
then.

> > Does that all make sense ?
> 
> Your code makes sense to me.  It's just the comment that confuses me.
> Does ID mean "implementation-defined behavior"?  That would be wrong:

Yes, that's what I meant by ID.

>        6.3.1.3  Signed and unsigned integers
> 
>        [#1] When a value with integer type is converted to  another
>        integer   type  other  than  _Bool,  if  the  value  can  be
>        represented by the new type, it is unchanged.
> 
>        [#2] Otherwise, if the new type is unsigned,  the  value  is
>        converted  by repeatedly adding or subtracting one more than
>        the maximum value that can be represented in  the  new  type
>        until the value is in the range of the new type.

That applies if the new type (uid_t, here) is unsigned.  But I think
uid_t's signedness is not specified, so it might be signed.  (SuS
says, in the section on types.h, only

  Additionally:
     * nlink_t, uid_t, gid_t, and id_t shall be integer types.

C99 6.3.1.3 continues:

         Otherwise, the new type is signed and the value cannot be
         represented in it; either the result is
         implementation-defined or an implementation-defined signal is
         raised.

So the type of uid_t is ID too.

> One more thing: please report errors with error_report().  Here:

>             error_report("Could not obtain uid");
> 
> No need to quote optarg back at the user, because error_report() already
> does.

Ah, I will do that.  Thanks.

Regards,
Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Ian Jackson <ian.jackson@eu.citrix.com> writes:
> > qemu_strtoul fails (returns an error) if the delimiter (that is, the
> > first character which is not processed as digit by strtoul) is not
> > '\0'.
> 
> It does that *only* when its @endptr argument is null.  Since you pass
> &ep, it should work fine here.

I have just read it again and you are right.  Sorry.  I will fix this
then.

> > Does that all make sense ?
> 
> Your code makes sense to me.  It's just the comment that confuses me.
> Does ID mean "implementation-defined behavior"?  That would be wrong:

Yes, that's what I meant by ID.

>        6.3.1.3  Signed and unsigned integers
> 
>        [#1] When a value with integer type is converted to  another
>        integer   type  other  than  _Bool,  if  the  value  can  be
>        represented by the new type, it is unchanged.
> 
>        [#2] Otherwise, if the new type is unsigned,  the  value  is
>        converted  by repeatedly adding or subtracting one more than
>        the maximum value that can be represented in  the  new  type
>        until the value is in the range of the new type.

That applies if the new type (uid_t, here) is unsigned.  But I think
uid_t's signedness is not specified, so it might be signed.  (SuS
says, in the section on types.h, only

  Additionally:
     * nlink_t, uid_t, gid_t, and id_t shall be integer types.

C99 6.3.1.3 continues:

         Otherwise, the new type is signed and the value cannot be
         represented in it; either the result is
         implementation-defined or an implementation-defined signal is
         raised.

So the type of uid_t is ID too.

> One more thing: please report errors with error_report().  Here:

>             error_report("Could not obtain uid");
> 
> No need to quote optarg back at the user, because error_report() already
> does.

Ah, I will do that.  Thanks.

Regards,
Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Actually, a numeric UID without group name or ID could be made to work
> just fine as long as it maps to a user name.  The use case may not be
> worth the bother, though.

In libxl's use case, it wouldn't map to a name.

> Using '.' to separate user and group is suboptimal, because POSIX
> portable user and group names may contain it:
...
> Coreutils uses ':'.  Let's follow its lead.

I'm happy to change it to use `:'.

Can you confirm that this command line interface is then OK ?
We would like to stablise the corresponding code in libxl...

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Actually, a numeric UID without group name or ID could be made to work
> just fine as long as it maps to a user name.  The use case may not be
> worth the bother, though.

In libxl's use case, it wouldn't map to a name.

> Using '.' to separate user and group is suboptimal, because POSIX
> portable user and group names may contain it:
...
> Coreutils uses ':'.  Let's follow its lead.

I'm happy to change it to use `:'.

Can you confirm that this command line interface is then OK ?
We would like to stablise the corresponding code in libxl...

Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Actually, a numeric UID without group name or ID could be made to work
> just fine as long as it maps to a user name.  The use case may not be
> worth the bother, though.

In libxl's use case, it wouldn't map to a name.

> Using '.' to separate user and group is suboptimal, because POSIX
> portable user and group names may contain it:
...
> Coreutils uses ':'.  Let's follow its lead.

I'm happy to change it to use `:'.

Can you confirm that this command line interface is then OK ?
We would like to stablise the corresponding code in libxl...

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
>> The last thing the QEMU command line needs is more exotic options.  Are
>> you sure we need a new one here?  Can we make existing -runas serve?
>> Precedence: Coreutils[*].  Pseudo-code:
>> 
>>     if argument is a decimal number starting with '+':
>>         user ID
>>     else if argument is a valid user name:
>>         user name
>>     else if argument is a valid user ID:
>>         user ID
>>     else:
>>         error
>
> I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
> sense to try to -runas <uid> because: you wouldn't have a username
> to pass to initgroups: not calling initgroups would be a bear trap;
> and otherwise we wouldn't know what gid to use.

Actually, a numeric UID without group name or ID could be made to work
just fine as long as it maps to a user name.  The use case may not be
worth the bother, though.

Using '.' to separate user and group is suboptimal, because POSIX
portable user and group names may contain it:

    3.426 User Name

    A string that is used to identify a user; see also User Database.
    To be portable across systems conforming to IEEE Std 1003.1-2001,
    the value is composed of characters from the portable filename
    character set.  The hyphen should not be used as the first character
    of a portable user name.

and

    3.276 Portable Filename Character Set

    The set of characters from which portable filenames are constructed.

        A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
        a b c d e f g h i j k l m n o p q r s t u v w x y z
        0 1 2 3 4 5 6 7 8 9 . _ -

http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap03.html

Coreutils uses ':'.  Let's follow its lead.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
>> The last thing the QEMU command line needs is more exotic options.  Are
>> you sure we need a new one here?  Can we make existing -runas serve?
>> Precedence: Coreutils[*].  Pseudo-code:
>> 
>>     if argument is a decimal number starting with '+':
>>         user ID
>>     else if argument is a valid user name:
>>         user name
>>     else if argument is a valid user ID:
>>         user ID
>>     else:
>>         error
>
> I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
> sense to try to -runas <uid> because: you wouldn't have a username
> to pass to initgroups: not calling initgroups would be a bear trap;
> and otherwise we wouldn't know what gid to use.

Actually, a numeric UID without group name or ID could be made to work
just fine as long as it maps to a user name.  The use case may not be
worth the bother, though.

Using '.' to separate user and group is suboptimal, because POSIX
portable user and group names may contain it:

    3.426 User Name

    A string that is used to identify a user; see also User Database.
    To be portable across systems conforming to IEEE Std 1003.1-2001,
    the value is composed of characters from the portable filename
    character set.  The hyphen should not be used as the first character
    of a portable user name.

and

    3.276 Portable Filename Character Set

    The set of characters from which portable filenames are constructed.

        A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
        a b c d e f g h i j k l m n o p q r s t u v w x y z
        0 1 2 3 4 5 6 7 8 9 . _ -

http://pubs.opengroup.org/onlinepubs/000095399/basedefs/xbd_chap03.html

Coreutils uses ':'.  Let's follow its lead.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

(resending, more competently this time)

Daniel P. Berrange writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Just use  getpwuid() to get the "struct passwd *", then change_process_uid()
> doesn't need any changes at all AFAICT.

See my comments in the commit message.  There may be multiple passwd
entries referring to a particular uid.  I think in this area it would
be better to expect the caller to be explicit, rather than taking
getpwuid's notion of the first one.

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Daniel P. Berrange writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Just use  getpwuid() to get the "struct passwd *", then change_process_uid()
> doesn't need any changes at all AFAICT.

See my comments in the commit message.  There may be multiple passwd
entries referring to a particular uid.  I think in this area it would
be better to expect the caller to be explicit, rather than taking
getpwuid's notion of the first one.

Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Daniel P. Berrange writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> Just use  getpwuid() to get the "struct passwd *", then change_process_uid()
> doesn't need any changes at all AFAICT.

See my comments in the commit message.  There may be multiple passwd
entries referring to a particular uid.  I think in this area it would
be better to expect the caller to be explicit, rather than taking
getpwuid's notion of the first one.

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Daniel P. Berrange]

On Mon, Oct 09, 2017 at 04:05:10PM +0100, Ian Jackson wrote:
> Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> > The last thing the QEMU command line needs is more exotic options.  Are
> > you sure we need a new one here?  Can we make existing -runas serve?
> > Precedence: Coreutils[*].  Pseudo-code:
> > 
> >     if argument is a decimal number starting with '+':
> >         user ID
> >     else if argument is a valid user name:
> >         user name
> >     else if argument is a valid user ID:
> >         user ID
> >     else:
> >         error
> 
> I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
> sense to try to -runas <uid> because: you wouldn't have a username
> to pass to initgroups: not calling initgroups would be a bear trap;
> and otherwise we wouldn't know what gid to use.

Just use  getpwuid() to get the "struct passwd *", then change_process_uid()
doesn't need any changes at all AFAICT.


Regards,
Daniel
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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Daniel P. Berrange]

On Mon, Oct 09, 2017 at 04:05:10PM +0100, Ian Jackson wrote:
> Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> > The last thing the QEMU command line needs is more exotic options.  Are
> > you sure we need a new one here?  Can we make existing -runas serve?
> > Precedence: Coreutils[*].  Pseudo-code:
> > 
> >     if argument is a decimal number starting with '+':
> >         user ID
> >     else if argument is a valid user name:
> >         user name
> >     else if argument is a valid user ID:
> >         user ID
> >     else:
> >         error
> 
> I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
> sense to try to -runas <uid> because: you wouldn't have a username
> to pass to initgroups: not calling initgroups would be a bear trap;
> and otherwise we wouldn't know what gid to use.

Just use  getpwuid() to get the "struct passwd *", then change_process_uid()
doesn't need any changes at all AFAICT.


Regards,
Daniel
-- 
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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

(resending to right address for xen-devel)

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> The last thing the QEMU command line needs is more exotic options.  Are
> you sure we need a new one here?  Can we make existing -runas serve?
> Precedence: Coreutils[*].  Pseudo-code:
> 
>     if argument is a decimal number starting with '+':
>         user ID
>     else if argument is a valid user name:
>         user name
>     else if argument is a valid user ID:
>         user ID
>     else:
>         error

I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
sense to try to -runas <uid> because: you wouldn't have a username
to pass to initgroups: not calling initgroups would be a bear trap;
and otherwise we wouldn't know what gid to use.

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> The last thing the QEMU command line needs is more exotic options.  Are
> you sure we need a new one here?  Can we make existing -runas serve?
> Precedence: Coreutils[*].  Pseudo-code:
> 
>     if argument is a decimal number starting with '+':
>         user ID
>     else if argument is a valid user name:
>         user name
>     else if argument is a valid user ID:
>         user ID
>     else:
>         error

I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
sense to try to -runas <uid> because: you wouldn't have a username
to pass to initgroups: not calling initgroups would be a bear trap;
and otherwise we wouldn't know what gid to use.

Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Markus Armbruster writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> The last thing the QEMU command line needs is more exotic options.  Are
> you sure we need a new one here?  Can we make existing -runas serve?
> Precedence: Coreutils[*].  Pseudo-code:
> 
>     if argument is a decimal number starting with '+':
>         user ID
>     else if argument is a valid user name:
>         user name
>     else if argument is a valid user ID:
>         user ID
>     else:
>         error

I can do this.  So -runas <uid>.<gid> then.  I don't think it makes
sense to try to -runas <uid> because: you wouldn't have a username
to pass to initgroups: not calling initgroups would be a bear trap;
and otherwise we wouldn't know what gid to use.

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
[...]
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9f6e2ad..34a5329 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
>  to the specified user.
>  ETEXI
>  
> +#ifndef _WIN32
> +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
> +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
> +    QEMU_ARCH_ALL)
> +#endif
> +STEXI
> +@item -runasid @var{uid}.@var{gid}
> +@findex -runasid
> +Immediately before starting guest execution, drop root privileges, switching
> +to the specified uid and gid.
> +ETEXI
> +
>  DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
>      "-prom-env variable=value\n"
>      "                set OpenBIOS nvram variables\n",

The last thing the QEMU command line needs is more exotic options.  Are
you sure we need a new one here?  Can we make existing -runas serve?
Precedence: Coreutils[*].  Pseudo-code:

    if argument is a decimal number starting with '+':
        user ID
    else if argument is a valid user name:
        user name
    else if argument is a valid user ID:
        user ID
    else:
        error

[*] https://www.gnu.org/software/coreutils/manual/html_node/Disambiguating-names-and-IDs.html

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Markus Armbruster]

Ian Jackson <ian.jackson@eu.citrix.com> writes:

> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
[...]
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 9f6e2ad..34a5329 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
>  to the specified user.
>  ETEXI
>  
> +#ifndef _WIN32
> +DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
> +    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
> +    QEMU_ARCH_ALL)
> +#endif
> +STEXI
> +@item -runasid @var{uid}.@var{gid}
> +@findex -runasid
> +Immediately before starting guest execution, drop root privileges, switching
> +to the specified uid and gid.
> +ETEXI
> +
>  DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
>      "-prom-env variable=value\n"
>      "                set OpenBIOS nvram variables\n",

The last thing the QEMU command line needs is more exotic options.  Are
you sure we need a new one here?  Can we make existing -runas serve?
Precedence: Coreutils[*].  Pseudo-code:

    if argument is a decimal number starting with '+':
        user ID
    else if argument is a valid user name:
        user name
    else if argument is a valid user ID:
        user ID
    else:
        error

[*] https://www.gnu.org/software/coreutils/manual/html_node/Disambiguating-names-and-IDs.html

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

(resending to fix xen-devel CC)

Peter Maydell writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> On 4 October 2017 at 17:18, Ian Jackson <ian.jackson@eu.citrix.com> wrote:
> >  static void change_process_uid(void)
> >  {
> > -    if (user_pwd) {
> > -        if (setgid(user_pwd->pw_gid) < 0) {
> > +    if (user_pwd || user_uid != (uid_t)-1) {
> > +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
> >              fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> 
> If you're changing the gid we pass to setgid() I think you should
> also change the value we tell the user we tried to use in the
> error message, or it could be rather confusing.

Thanks for the review.  Sorry about the mess here.  I have fixed all
these problems.

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Ross Lagerwall writes ("Re: [PATCH 7/8] os-posix: Provide new -runasid option"):
> On 10/04/2017 05:18 PM, Ian Jackson wrote:
> > -        if (setuid(user_pwd->pw_uid) < 0) {
> > +        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
> >               fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
> >               exit(1);
> >           }
> 
> This last one should be user_uid, not user_gid.

Thanks, fixed.

Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Peter Maydell writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> On 4 October 2017 at 17:18, Ian Jackson <ian.jackson@eu.citrix.com> wrote:
> >  static void change_process_uid(void)
> >  {
> > -    if (user_pwd) {
> > -        if (setgid(user_pwd->pw_gid) < 0) {
> > +    if (user_pwd || user_uid != (uid_t)-1) {
> > +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
> >              fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> 
> If you're changing the gid we pass to setgid() I think you should
> also change the value we tell the user we tried to use in the
> error message, or it could be rather confusing.

Thanks for the review.  Sorry about the mess here.  I have fixed all
these problems.

Ian.

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

Peter Maydell writes ("Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option"):
> On 4 October 2017 at 17:18, Ian Jackson <ian.jackson@eu.citrix.com> wrote:
> >  static void change_process_uid(void)
> >  {
> > -    if (user_pwd) {
> > -        if (setgid(user_pwd->pw_gid) < 0) {
> > +    if (user_pwd || user_uid != (uid_t)-1) {
> > +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
> >              fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
> 
> If you're changing the gid we pass to setgid() I think you should
> also change the value we tell the user we tried to use in the
> error message, or it could be rather confusing.

Thanks for the review.  Sorry about the mess here.  I have fixed all
these problems.

Ian.

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Peter Maydell]

On 4 October 2017 at 17:18, Ian Jackson <ian.jackson@eu.citrix.com> wrote:
> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> ---


> @@ -166,17 +187,19 @@ void os_parse_cmd_args(int index, const char *optarg)
>
>  static void change_process_uid(void)
>  {
> -    if (user_pwd) {
> -        if (setgid(user_pwd->pw_gid) < 0) {
> +    if (user_pwd || user_uid != (uid_t)-1) {
> +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
>              fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);

If you're changing the gid we pass to setgid() I think you should
also change the value we tell the user we tried to use in the
error message, or it could be rather confusing.

>              exit(1);
>          }
> -        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> +        if ((user_pwd
> +             ? initgroups(user_pwd->pw_name, user_pwd->pw_gid)
> +             : setgroups(1, &user_gid)) < 0) {
>              fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
>                      user_pwd->pw_name, user_pwd->pw_gid);

...and here we might claim we failed initgroups() when we actually
failed setgroups().

>              exit(1);
>          }
> -        if (setuid(user_pwd->pw_uid) < 0) {
> +        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
>              fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);

This error message should be updated too.

thanks
-- PMM

Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Peter Maydell]

On 4 October 2017 at 17:18, Ian Jackson <ian.jackson@eu.citrix.com> wrote:
> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
>
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
> ---


> @@ -166,17 +187,19 @@ void os_parse_cmd_args(int index, const char *optarg)
>
>  static void change_process_uid(void)
>  {
> -    if (user_pwd) {
> -        if (setgid(user_pwd->pw_gid) < 0) {
> +    if (user_pwd || user_uid != (uid_t)-1) {
> +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
>              fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);

If you're changing the gid we pass to setgid() I think you should
also change the value we tell the user we tried to use in the
error message, or it could be rather confusing.

>              exit(1);
>          }
> -        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> +        if ((user_pwd
> +             ? initgroups(user_pwd->pw_name, user_pwd->pw_gid)
> +             : setgroups(1, &user_gid)) < 0) {
>              fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
>                      user_pwd->pw_name, user_pwd->pw_gid);

...and here we might claim we failed initgroups() when we actually
failed setgroups().

>              exit(1);
>          }
> -        if (setuid(user_pwd->pw_uid) < 0) {
> +        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
>              fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);

This error message should be updated too.

thanks
-- PMM

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Re: [Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ross Lagerwall]

On 10/04/2017 05:18 PM, Ian Jackson wrote:
> This allows the caller to specify a uid and gid to use, even if there
> is no corresponding password entry.  This will be useful in certain
> Xen configurations.
> 
> Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
snip
> @@ -166,17 +187,19 @@ void os_parse_cmd_args(int index, const char *optarg)
>   
>   static void change_process_uid(void)
>   {
> -    if (user_pwd) {
> -        if (setgid(user_pwd->pw_gid) < 0) {
> +    if (user_pwd || user_uid != (uid_t)-1) {
> +        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
>               fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
>               exit(1);
>           }
> -        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
> +        if ((user_pwd
> +             ? initgroups(user_pwd->pw_name, user_pwd->pw_gid)
> +             : setgroups(1, &user_gid)) < 0) {
>               fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
>                       user_pwd->pw_name, user_pwd->pw_gid);
>               exit(1);
>           }
> -        if (setuid(user_pwd->pw_uid) < 0) {
> +        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
>               fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
>               exit(1);
>           }

This last one should be user_uid, not user_gid.

-- 
Ross Lagerwall

[Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

This allows the caller to specify a uid and gid to use, even if there
is no corresponding password entry.  This will be useful in certain
Xen configurations.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Coding style fixes.
---
 os-posix.c      | 31 +++++++++++++++++++++++++++----
 qemu-options.hx | 12 ++++++++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/os-posix.c b/os-posix.c
index 92e9d85..d63680b 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -43,6 +43,8 @@
 #endif
 
 static struct passwd *user_pwd;
+static uid_t user_uid = (uid_t)-1;
+static gid_t user_gid = (gid_t)-1;
 static const char *chroot_dir;
 static int daemonize;
 static int daemon_pipe;
@@ -134,6 +136,9 @@ void os_set_proc_name(const char *s)
  */
 void os_parse_cmd_args(int index, const char *optarg)
 {
+    unsigned long lv;
+    char *ep;
+    int rc;
     switch (index) {
 #ifdef CONFIG_SLIRP
     case QEMU_OPTION_smb:
@@ -150,6 +155,22 @@ void os_parse_cmd_args(int index, const char *optarg)
             exit(1);
         }
         break;
+    case QEMU_OPTION_runasid:
+        errno = 0;
+        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
+        user_uid = lv; /* overflow here is ID in C99 */
+        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
+            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
+            exit(1);
+        }
+        lv = 0;
+        rc = qemu_strtoul(ep + 1, 0, 0, &lv);
+        user_gid = lv; /* overflow here is ID in C99 */
+        if (rc || user_gid != lv || user_gid == (gid_t)-1) {
+            fprintf(stderr, "Could not obtain gid from \"%s\"", optarg);
+            exit(1);
+        }
+        break;
     case QEMU_OPTION_chroot:
         chroot_dir = optarg;
         break;
@@ -166,17 +187,19 @@ void os_parse_cmd_args(int index, const char *optarg)
 
 static void change_process_uid(void)
 {
-    if (user_pwd) {
-        if (setgid(user_pwd->pw_gid) < 0) {
+    if (user_pwd || user_uid != (uid_t)-1) {
+        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
             exit(1);
         }
-        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
+        if ((user_pwd
+             ? initgroups(user_pwd->pw_name, user_pwd->pw_gid)
+             : setgroups(1, &user_gid)) < 0) {
             fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
                     user_pwd->pw_name, user_pwd->pw_gid);
             exit(1);
         }
-        if (setuid(user_pwd->pw_uid) < 0) {
+        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
             exit(1);
         }
diff --git a/qemu-options.hx b/qemu-options.hx
index 9f6e2ad..34a5329 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
 to the specified user.
 ETEXI
 
+#ifndef _WIN32
+DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
+    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
+    QEMU_ARCH_ALL)
+#endif
+STEXI
+@item -runasid @var{uid}.@var{gid}
+@findex -runasid
+Immediately before starting guest execution, drop root privileges, switching
+to the specified uid and gid.
+ETEXI
+
 DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
     "-prom-env variable=value\n"
     "                set OpenBIOS nvram variables\n",
-- 
2.1.4

[Qemu-devel] [PATCH 7/8] os-posix: Provide new -runasid option

[Ian Jackson]

This allows the caller to specify a uid and gid to use, even if there
is no corresponding password entry.  This will be useful in certain
Xen configurations.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: Coding style fixes.
---
 os-posix.c      | 31 +++++++++++++++++++++++++++----
 qemu-options.hx | 12 ++++++++++++
 2 files changed, 39 insertions(+), 4 deletions(-)

diff --git a/os-posix.c b/os-posix.c
index 92e9d85..d63680b 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -43,6 +43,8 @@
 #endif
 
 static struct passwd *user_pwd;
+static uid_t user_uid = (uid_t)-1;
+static gid_t user_gid = (gid_t)-1;
 static const char *chroot_dir;
 static int daemonize;
 static int daemon_pipe;
@@ -134,6 +136,9 @@ void os_set_proc_name(const char *s)
  */
 void os_parse_cmd_args(int index, const char *optarg)
 {
+    unsigned long lv;
+    char *ep;
+    int rc;
     switch (index) {
 #ifdef CONFIG_SLIRP
     case QEMU_OPTION_smb:
@@ -150,6 +155,22 @@ void os_parse_cmd_args(int index, const char *optarg)
             exit(1);
         }
         break;
+    case QEMU_OPTION_runasid:
+        errno = 0;
+        lv = strtoul(optarg, &ep, 0); /* can't qemu_strtoul, want *ep=='.' */
+        user_uid = lv; /* overflow here is ID in C99 */
+        if (errno || *ep != '.' || user_uid != lv || user_uid == (uid_t)-1) {
+            fprintf(stderr, "Could not obtain uid from \"%s\"", optarg);
+            exit(1);
+        }
+        lv = 0;
+        rc = qemu_strtoul(ep + 1, 0, 0, &lv);
+        user_gid = lv; /* overflow here is ID in C99 */
+        if (rc || user_gid != lv || user_gid == (gid_t)-1) {
+            fprintf(stderr, "Could not obtain gid from \"%s\"", optarg);
+            exit(1);
+        }
+        break;
     case QEMU_OPTION_chroot:
         chroot_dir = optarg;
         break;
@@ -166,17 +187,19 @@ void os_parse_cmd_args(int index, const char *optarg)
 
 static void change_process_uid(void)
 {
-    if (user_pwd) {
-        if (setgid(user_pwd->pw_gid) < 0) {
+    if (user_pwd || user_uid != (uid_t)-1) {
+        if (setgid(user_pwd ? user_pwd->pw_gid : user_gid) < 0) {
             fprintf(stderr, "Failed to setgid(%d)\n", user_pwd->pw_gid);
             exit(1);
         }
-        if (initgroups(user_pwd->pw_name, user_pwd->pw_gid) < 0) {
+        if ((user_pwd
+             ? initgroups(user_pwd->pw_name, user_pwd->pw_gid)
+             : setgroups(1, &user_gid)) < 0) {
             fprintf(stderr, "Failed to initgroups(\"%s\", %d)\n",
                     user_pwd->pw_name, user_pwd->pw_gid);
             exit(1);
         }
-        if (setuid(user_pwd->pw_uid) < 0) {
+        if (setuid(user_pwd ? user_pwd->pw_uid : user_gid) < 0) {
             fprintf(stderr, "Failed to setuid(%d)\n", user_pwd->pw_uid);
             exit(1);
         }
diff --git a/qemu-options.hx b/qemu-options.hx
index 9f6e2ad..34a5329 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -3968,6 +3968,18 @@ Immediately before starting guest execution, drop root privileges, switching
 to the specified user.
 ETEXI
 
+#ifndef _WIN32
+DEF("runasid", HAS_ARG, QEMU_OPTION_runasid, \
+    "-runasid uid.gid     change to numeric uid and gid just before starting the VM\n",
+    QEMU_ARCH_ALL)
+#endif
+STEXI
+@item -runasid @var{uid}.@var{gid}
+@findex -runasid
+Immediately before starting guest execution, drop root privileges, switching
+to the specified uid and gid.
+ETEXI
+
 DEF("prom-env", HAS_ARG, QEMU_OPTION_prom_env,
     "-prom-env variable=value\n"
     "                set OpenBIOS nvram variables\n",
-- 
2.1.4