* [RFC 0/5] Clean up error handling in libvhost-user memory mapping
@ 2021-12-15 22:29 Raphael Norwitz
2021-12-15 22:29 ` [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation Raphael Norwitz
` (5 more replies)
0 siblings, 6 replies; 14+ messages in thread
From: Raphael Norwitz @ 2021-12-15 22:29 UTC (permalink / raw)
To: stefanha, marcandre.lureau, mst, david
Cc: raphael.s.norwitz, qemu-devel, Raphael Norwitz
Hey Stefan, Marc-Andre, MST, David -
As promised here is a series cleaning up error handling in the
libvhost-user memory mapping path. Most of these cleanups are
straightforward and have been discussed on the mailing list in threads
[1] and [2]. Hopefully there is nothing super controversial in the first
4 patches.
I am concerned about is patch 5 “libvhost-user: handle removal of
identical regions”. From my reading of Stefan's comments in [1], the
proposal seemed to be to remove any duplicate regions. I’d prefer to
prevent duplicate regions from being added in the first place. Thoughts?
[1] https://lore.kernel.org/qemu-devel/20211018143319.GA11006@raphael-debian-dev/
[2] https://lore.kernel.org/qemu-devel/9391f500-70be-26cf-bcfc-591d3ee84d4e@redhat.com/
Sorry for the delay,
Raphael
David Hildenbrand (1):
libvhost-user: Simplify VHOST_USER_REM_MEM_REG
Raphael Norwitz (4):
libvhost-user: Add vu_rem_mem_reg input validation
libvhost-user: Add vu_add_mem_reg input validation
libvhost-user: prevent over-running max RAM slots
libvhost-user: handle removal of identical regions
subprojects/libvhost-user/libvhost-user.c | 52 +++++++++++++++--------
1 file changed, 34 insertions(+), 18 deletions(-)
--
2.20.1
^ permalink raw reply [flat|nested] 14+ messages in thread
* [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
@ 2021-12-15 22:29 ` Raphael Norwitz
2022-01-05 11:00 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 2/5] libvhost-user: Add vu_add_mem_reg " Raphael Norwitz
` (4 subsequent siblings)
5 siblings, 1 reply; 14+ messages in thread
From: Raphael Norwitz @ 2021-12-15 22:29 UTC (permalink / raw)
To: stefanha, marcandre.lureau, mst, david
Cc: raphael.s.norwitz, qemu-devel, Raphael Norwitz
Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
subprojects/libvhost-user/libvhost-user.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 787f4d2d4f..573212a83b 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -801,6 +801,12 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
VuDevRegion shadow_regions[VHOST_USER_MAX_RAM_SLOTS] = {};
VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
+ if (vmsg->fd_num != 1 ||
+ vmsg->size != sizeof(vmsg->payload.memreg)) {
+ vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
+ return true;
+ }
+
DPRINT("Removing region:\n");
DPRINT(" guest_phys_addr: 0x%016"PRIx64"\n",
msg_region->guest_phys_addr);
--
2.20.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [RFC 2/5] libvhost-user: Add vu_add_mem_reg input validation
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
2021-12-15 22:29 ` [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation Raphael Norwitz
@ 2021-12-15 22:29 ` Raphael Norwitz
2022-01-05 11:02 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 3/5] libvhost-user: Simplify VHOST_USER_REM_MEM_REG Raphael Norwitz
` (3 subsequent siblings)
5 siblings, 1 reply; 14+ messages in thread
From: Raphael Norwitz @ 2021-12-15 22:29 UTC (permalink / raw)
To: stefanha, marcandre.lureau, mst, david
Cc: raphael.s.norwitz, qemu-devel, Raphael Norwitz
Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
subprojects/libvhost-user/libvhost-user.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 573212a83b..80ef335254 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -690,6 +690,12 @@ vu_add_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
VuDevRegion *dev_region = &dev->regions[dev->nregions];
void *mmap_addr;
+ if (vmsg->fd_num != 1 ||
+ vmsg->size != sizeof(vmsg->payload.memreg)) {
+ vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
+ return true;
+ }
+
/*
* If we are in postcopy mode and we receive a u64 payload with a 0 value
* we know all the postcopy client bases have been received, and we
--
2.20.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [RFC 3/5] libvhost-user: Simplify VHOST_USER_REM_MEM_REG
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
2021-12-15 22:29 ` [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation Raphael Norwitz
2021-12-15 22:29 ` [RFC 2/5] libvhost-user: Add vu_add_mem_reg " Raphael Norwitz
@ 2021-12-15 22:29 ` Raphael Norwitz
2022-01-05 11:04 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 4/5] libvhost-user: prevent over-running max RAM slots Raphael Norwitz
` (2 subsequent siblings)
5 siblings, 1 reply; 14+ messages in thread
From: Raphael Norwitz @ 2021-12-15 22:29 UTC (permalink / raw)
To: stefanha, marcandre.lureau, mst, david
Cc: raphael.s.norwitz, qemu-devel, Raphael Norwitz
From: David Hildenbrand <david@redhat.com>
Let's avoid having to manually copy all elements. Copy only the ones
necessary to close the hole and perform the operation in-place without
a second array.
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
subprojects/libvhost-user/libvhost-user.c | 30 +++++++++++------------
1 file changed, 14 insertions(+), 16 deletions(-)
diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 80ef335254..714cc7e08b 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -802,10 +802,8 @@ static inline bool reg_equal(VuDevRegion *vudev_reg,
static bool
vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
- int i, j;
- bool found = false;
- VuDevRegion shadow_regions[VHOST_USER_MAX_RAM_SLOTS] = {};
VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
+ int i;
if (vmsg->fd_num != 1 ||
vmsg->size != sizeof(vmsg->payload.memreg)) {
@@ -823,28 +821,28 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
DPRINT(" mmap_offset 0x%016"PRIx64"\n",
msg_region->mmap_offset);
- for (i = 0, j = 0; i < dev->nregions; i++) {
- if (!reg_equal(&dev->regions[i], msg_region)) {
- shadow_regions[j].gpa = dev->regions[i].gpa;
- shadow_regions[j].size = dev->regions[i].size;
- shadow_regions[j].qva = dev->regions[i].qva;
- shadow_regions[j].mmap_addr = dev->regions[i].mmap_addr;
- shadow_regions[j].mmap_offset = dev->regions[i].mmap_offset;
- j++;
- } else {
- found = true;
+ for (i = 0; i < dev->nregions; i++) {
+ if (reg_equal(&dev->regions[i], msg_region)) {
VuDevRegion *r = &dev->regions[i];
void *m = (void *) (uintptr_t) r->mmap_addr;
if (m) {
munmap(m, r->size + r->mmap_offset);
}
+
+ break;
}
}
- if (found) {
- memcpy(dev->regions, shadow_regions,
- sizeof(VuDevRegion) * VHOST_USER_MAX_RAM_SLOTS);
+ if (i < dev->nregions) {
+ /*
+ * Shift all affected entries by 1 to close the hole at index i and
+ * zero out the last entry.
+ */
+ memmove(dev->regions + i, dev->regions + i + 1,
+ sizeof(VuDevRegion) * (dev->nregions - i - 1));
+ memset(dev->regions + dev->nregions - 1, 0,
+ sizeof(VuDevRegion));
DPRINT("Successfully removed a region\n");
dev->nregions--;
vmsg_set_reply_u64(vmsg, 0);
--
2.20.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [RFC 4/5] libvhost-user: prevent over-running max RAM slots
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
` (2 preceding siblings ...)
2021-12-15 22:29 ` [RFC 3/5] libvhost-user: Simplify VHOST_USER_REM_MEM_REG Raphael Norwitz
@ 2021-12-15 22:29 ` Raphael Norwitz
2022-01-05 11:06 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 5/5] libvhost-user: handle removal of identical regions Raphael Norwitz
2022-01-04 15:46 ` [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
5 siblings, 1 reply; 14+ messages in thread
From: Raphael Norwitz @ 2021-12-15 22:29 UTC (permalink / raw)
To: stefanha, marcandre.lureau, mst, david
Cc: raphael.s.norwitz, qemu-devel, Raphael Norwitz
When VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS support was added to
libvhost-user, no guardrails were added to protect against QEMU
attempting to hot-add too many RAM slots to a VM with a libvhost-user
based backed attached.
This change adds the missing error handling by introducing a check on
the number of RAM slots the device has available before proceeding to
process the VHOST_USER_ADD_MEM_REG message.
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
subprojects/libvhost-user/libvhost-user.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 714cc7e08b..74a9980194 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -690,6 +690,11 @@ vu_add_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
VuDevRegion *dev_region = &dev->regions[dev->nregions];
void *mmap_addr;
+ if (dev->nregions == VHOST_USER_MAX_RAM_SLOTS) {
+ vu_panic(dev, "No free ram slots available");
+ return true;
+ }
+
if (vmsg->fd_num != 1 ||
vmsg->size != sizeof(vmsg->payload.memreg)) {
vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
--
2.20.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [RFC 5/5] libvhost-user: handle removal of identical regions
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
` (3 preceding siblings ...)
2021-12-15 22:29 ` [RFC 4/5] libvhost-user: prevent over-running max RAM slots Raphael Norwitz
@ 2021-12-15 22:29 ` Raphael Norwitz
2022-01-05 11:18 ` Stefan Hajnoczi
2022-01-04 15:46 ` [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
5 siblings, 1 reply; 14+ messages in thread
From: Raphael Norwitz @ 2021-12-15 22:29 UTC (permalink / raw)
To: stefanha, marcandre.lureau, mst, david
Cc: raphael.s.norwitz, qemu-devel, Raphael Norwitz
Today if QEMU (or any other VMM) has sent multiple copies of the same
region to a libvhost-user based backend and then attempts to remove the
region, only one instance of the region will be removed, leaving stale
copies of the region in dev->regions[].
This change resolves this by having vu_rem_mem_reg() iterate through all
regions in dev->regions[] and delete all matching regions.
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
---
subprojects/libvhost-user/libvhost-user.c | 27 ++++++++++++-----------
1 file changed, 14 insertions(+), 13 deletions(-)
diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 74a9980194..2f465a4f0e 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -809,6 +809,7 @@ static bool
vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
int i;
+ bool found = false;
if (vmsg->fd_num != 1 ||
vmsg->size != sizeof(vmsg->payload.memreg)) {
@@ -831,25 +832,25 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
VuDevRegion *r = &dev->regions[i];
void *m = (void *) (uintptr_t) r->mmap_addr;
- if (m) {
+ if (m && !found) {
munmap(m, r->size + r->mmap_offset);
}
- break;
+ /*
+ * Shift all affected entries by 1 to close the hole at index i and
+ * zero out the last entry.
+ */
+ memmove(dev->regions + i, dev->regions + i + 1,
+ sizeof(VuDevRegion) * (dev->nregions - i - 1));
+ memset(dev->regions + dev->nregions - 1, 0, sizeof(VuDevRegion));
+ DPRINT("Successfully removed a region\n");
+ dev->nregions--;
+
+ found = true;
}
}
- if (i < dev->nregions) {
- /*
- * Shift all affected entries by 1 to close the hole at index i and
- * zero out the last entry.
- */
- memmove(dev->regions + i, dev->regions + i + 1,
- sizeof(VuDevRegion) * (dev->nregions - i - 1));
- memset(dev->regions + dev->nregions - 1, 0,
- sizeof(VuDevRegion));
- DPRINT("Successfully removed a region\n");
- dev->nregions--;
+ if (found) {
vmsg_set_reply_u64(vmsg, 0);
} else {
vu_panic(dev, "Specified region not found\n");
--
2.20.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [RFC 0/5] Clean up error handling in libvhost-user memory mapping
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
` (4 preceding siblings ...)
2021-12-15 22:29 ` [RFC 5/5] libvhost-user: handle removal of identical regions Raphael Norwitz
@ 2022-01-04 15:46 ` Raphael Norwitz
5 siblings, 0 replies; 14+ messages in thread
From: Raphael Norwitz @ 2022-01-04 15:46 UTC (permalink / raw)
To: mst; +Cc: raphael.s.norwitz, david, mst, qemu-devel, stefanha, marcandre.lureau
Ping
On Wed, Dec 15, 2021 at 10:29:46PM +0000, Raphael Norwitz wrote:
> Hey Stefan, Marc-Andre, MST, David -
>
> As promised here is a series cleaning up error handling in the
> libvhost-user memory mapping path. Most of these cleanups are
> straightforward and have been discussed on the mailing list in threads
> [1] and [2]. Hopefully there is nothing super controversial in the first
> 4 patches.
>
> I am concerned about patch 5 “libvhost-user: handle removal of
> identical regions”. From my reading of Stefan's comments in [1], the
> proposal seemed to be to remove any duplicate regions. I’d prefer to
> prevent duplicate regions from being added in the first place. Thoughts?
>
> [1] https://lore.kernel.org/qemu-devel/20211018143319.GA11006@raphael-debian-dev/
> [2] https://lore.kernel.org/qemu-devel/9391f500-70be-26cf-bcfc-591d3ee84d4e@redhat.com/
>
> Sorry for the delay,
> Raphael
>
> David Hildenbrand (1):
> libvhost-user: Simplify VHOST_USER_REM_MEM_REG
>
> Raphael Norwitz (4):
> libvhost-user: Add vu_rem_mem_reg input validation
> libvhost-user: Add vu_add_mem_reg input validation
> libvhost-user: prevent over-running max RAM slots
> libvhost-user: handle removal of identical regions
>
> subprojects/libvhost-user/libvhost-user.c | 52 +++++++++++++++--------
> 1 file changed, 34 insertions(+), 18 deletions(-)
>
> --
> 2.20.1
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation
2021-12-15 22:29 ` [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation Raphael Norwitz
@ 2022-01-05 11:00 ` Stefan Hajnoczi
2022-01-06 5:13 ` Raphael Norwitz
0 siblings, 1 reply; 14+ messages in thread
From: Stefan Hajnoczi @ 2022-01-05 11:00 UTC (permalink / raw)
To: Raphael Norwitz
Cc: marcandre.lureau, david, qemu-devel, raphael.s.norwitz, mst
[-- Attachment #1: Type: text/plain, Size: 1338 bytes --]
On Wed, Dec 15, 2021 at 10:29:48PM +0000, Raphael Norwitz wrote:
> Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
> ---
> subprojects/libvhost-user/libvhost-user.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index 787f4d2d4f..573212a83b 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -801,6 +801,12 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> VuDevRegion shadow_regions[VHOST_USER_MAX_RAM_SLOTS] = {};
> VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
>
> + if (vmsg->fd_num != 1 ||
> + vmsg->size != sizeof(vmsg->payload.memreg)) {
> + vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
> + return true;
Most vu_panic() callers return false to indicate that a reply does not
need to be sent. When the return value is true vu_dispatch() sends a
response, which we don't want.
Note that vu_dispatch() returns true (success) when the message handler
function returns false. The success/failure behavior should probably be
separated from the reply_requested behavior :(.
Anyway, returning false is probably appropriate here.
Stefan
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^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 2/5] libvhost-user: Add vu_add_mem_reg input validation
2021-12-15 22:29 ` [RFC 2/5] libvhost-user: Add vu_add_mem_reg " Raphael Norwitz
@ 2022-01-05 11:02 ` Stefan Hajnoczi
0 siblings, 0 replies; 14+ messages in thread
From: Stefan Hajnoczi @ 2022-01-05 11:02 UTC (permalink / raw)
To: Raphael Norwitz
Cc: marcandre.lureau, david, qemu-devel, raphael.s.norwitz, mst
[-- Attachment #1: Type: text/plain, Size: 901 bytes --]
On Wed, Dec 15, 2021 at 10:29:51PM +0000, Raphael Norwitz wrote:
> Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
> ---
> subprojects/libvhost-user/libvhost-user.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index 573212a83b..80ef335254 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -690,6 +690,12 @@ vu_add_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> VuDevRegion *dev_region = &dev->regions[dev->nregions];
> void *mmap_addr;
>
> + if (vmsg->fd_num != 1 ||
> + vmsg->size != sizeof(vmsg->payload.memreg)) {
> + vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
> + return true;
return false - we don't want a reply to be sent.
Stefan
[-- Attachment #2: signature.asc --]
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^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 3/5] libvhost-user: Simplify VHOST_USER_REM_MEM_REG
2021-12-15 22:29 ` [RFC 3/5] libvhost-user: Simplify VHOST_USER_REM_MEM_REG Raphael Norwitz
@ 2022-01-05 11:04 ` Stefan Hajnoczi
0 siblings, 0 replies; 14+ messages in thread
From: Stefan Hajnoczi @ 2022-01-05 11:04 UTC (permalink / raw)
To: Raphael Norwitz
Cc: marcandre.lureau, david, qemu-devel, raphael.s.norwitz, mst
[-- Attachment #1: Type: text/plain, Size: 594 bytes --]
On Wed, Dec 15, 2021 at 10:29:52PM +0000, Raphael Norwitz wrote:
> From: David Hildenbrand <david@redhat.com>
>
> Let's avoid having to manually copy all elements. Copy only the ones
> necessary to close the hole and perform the operation in-place without
> a second array.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
> ---
> subprojects/libvhost-user/libvhost-user.c | 30 +++++++++++------------
> 1 file changed, 14 insertions(+), 16 deletions(-)
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 488 bytes --]
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 4/5] libvhost-user: prevent over-running max RAM slots
2021-12-15 22:29 ` [RFC 4/5] libvhost-user: prevent over-running max RAM slots Raphael Norwitz
@ 2022-01-05 11:06 ` Stefan Hajnoczi
0 siblings, 0 replies; 14+ messages in thread
From: Stefan Hajnoczi @ 2022-01-05 11:06 UTC (permalink / raw)
To: Raphael Norwitz
Cc: marcandre.lureau, david, qemu-devel, raphael.s.norwitz, mst
[-- Attachment #1: Type: text/plain, Size: 1302 bytes --]
On Wed, Dec 15, 2021 at 10:29:54PM +0000, Raphael Norwitz wrote:
> When VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS support was added to
> libvhost-user, no guardrails were added to protect against QEMU
> attempting to hot-add too many RAM slots to a VM with a libvhost-user
> based backed attached.
>
> This change adds the missing error handling by introducing a check on
> the number of RAM slots the device has available before proceeding to
> process the VHOST_USER_ADD_MEM_REG message.
>
> Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
> Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
> ---
> subprojects/libvhost-user/libvhost-user.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index 714cc7e08b..74a9980194 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -690,6 +690,11 @@ vu_add_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> VuDevRegion *dev_region = &dev->regions[dev->nregions];
> void *mmap_addr;
>
> + if (dev->nregions == VHOST_USER_MAX_RAM_SLOTS) {
> + vu_panic(dev, "No free ram slots available");
> + return true;
return false
Stefan
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^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 5/5] libvhost-user: handle removal of identical regions
2021-12-15 22:29 ` [RFC 5/5] libvhost-user: handle removal of identical regions Raphael Norwitz
@ 2022-01-05 11:18 ` Stefan Hajnoczi
2022-01-06 5:36 ` Raphael Norwitz
0 siblings, 1 reply; 14+ messages in thread
From: Stefan Hajnoczi @ 2022-01-05 11:18 UTC (permalink / raw)
To: Raphael Norwitz
Cc: marcandre.lureau, david, qemu-devel, raphael.s.norwitz, mst
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On Wed, Dec 15, 2021 at 10:29:55PM +0000, Raphael Norwitz wrote:
> diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> index 74a9980194..2f465a4f0e 100644
> --- a/subprojects/libvhost-user/libvhost-user.c
> +++ b/subprojects/libvhost-user/libvhost-user.c
> @@ -809,6 +809,7 @@ static bool
> vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
> int i;
> + bool found = false;
>
> if (vmsg->fd_num != 1 ||
> vmsg->size != sizeof(vmsg->payload.memreg)) {
> @@ -831,25 +832,25 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> VuDevRegion *r = &dev->regions[i];
> void *m = (void *) (uintptr_t) r->mmap_addr;
>
> - if (m) {
> + if (m && !found) {
> munmap(m, r->size + r->mmap_offset);
> }
Why is only the first region unmapped? My interpretation of
vu_add_mem_reg() is that it mmaps duplicate regions to unique mmap_addr
addresses, so we need to munmap each of them.
>
> - break;
> + /*
> + * Shift all affected entries by 1 to close the hole at index i and
> + * zero out the last entry.
> + */
> + memmove(dev->regions + i, dev->regions + i + 1,
> + sizeof(VuDevRegion) * (dev->nregions - i - 1));
> + memset(dev->regions + dev->nregions - 1, 0, sizeof(VuDevRegion));
> + DPRINT("Successfully removed a region\n");
> + dev->nregions--;
> +
> + found = true;
> }
i-- is missing. dev->regions[] has been shortened so we need to check
the same element again.
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^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation
2022-01-05 11:00 ` Stefan Hajnoczi
@ 2022-01-06 5:13 ` Raphael Norwitz
0 siblings, 0 replies; 14+ messages in thread
From: Raphael Norwitz @ 2022-01-06 5:13 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: raphael.s.norwitz, mst, david, qemu-devel, Raphael Norwitz,
marcandre.lureau
On Wed, Jan 05, 2022 at 11:00:35AM +0000, Stefan Hajnoczi wrote:
> On Wed, Dec 15, 2021 at 10:29:48PM +0000, Raphael Norwitz wrote:
> > Signed-off-by: Raphael Norwitz <raphael.norwitz@nutanix.com>
> > ---
> > subprojects/libvhost-user/libvhost-user.c | 6 ++++++
> > 1 file changed, 6 insertions(+)
> >
> > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> > index 787f4d2d4f..573212a83b 100644
> > --- a/subprojects/libvhost-user/libvhost-user.c
> > +++ b/subprojects/libvhost-user/libvhost-user.c
> > @@ -801,6 +801,12 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> > VuDevRegion shadow_regions[VHOST_USER_MAX_RAM_SLOTS] = {};
> > VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
> >
> > + if (vmsg->fd_num != 1 ||
> > + vmsg->size != sizeof(vmsg->payload.memreg)) {
> > + vu_panic(dev, "VHOST_USER_REM_MEM_REG received multiple regions");
> > + return true;
>
> Most vu_panic() callers return false to indicate that a reply does not
> need to be sent. When the return value is true vu_dispatch() sends a
> response, which we don't want.
>
> Note that vu_dispatch() returns true (success) when the message handler
> function returns false. The success/failure behavior should probably be
> separated from the reply_requested behavior :(.
>
> Anyway, returning false is probably appropriate here.
>
Ack - I'll fix it in all the patches.
> Stefan
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [RFC 5/5] libvhost-user: handle removal of identical regions
2022-01-05 11:18 ` Stefan Hajnoczi
@ 2022-01-06 5:36 ` Raphael Norwitz
0 siblings, 0 replies; 14+ messages in thread
From: Raphael Norwitz @ 2022-01-06 5:36 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: raphael.s.norwitz, mst, david, qemu-devel, Raphael Norwitz,
marcandre.lureau
On Wed, Jan 05, 2022 at 11:18:52AM +0000, Stefan Hajnoczi wrote:
> On Wed, Dec 15, 2021 at 10:29:55PM +0000, Raphael Norwitz wrote:
> > diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
> > index 74a9980194..2f465a4f0e 100644
> > --- a/subprojects/libvhost-user/libvhost-user.c
> > +++ b/subprojects/libvhost-user/libvhost-user.c
> > @@ -809,6 +809,7 @@ static bool
> > vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> > VhostUserMemoryRegion m = vmsg->payload.memreg.region, *msg_region = &m;
> > int i;
> > + bool found = false;
> >
> > if (vmsg->fd_num != 1 ||
> > vmsg->size != sizeof(vmsg->payload.memreg)) {
> > @@ -831,25 +832,25 @@ vu_rem_mem_reg(VuDev *dev, VhostUserMsg *vmsg) {
> > VuDevRegion *r = &dev->regions[i];
> > void *m = (void *) (uintptr_t) r->mmap_addr;
> >
> > - if (m) {
> > + if (m && !found) {
> > munmap(m, r->size + r->mmap_offset);
> > }
>
> Why is only the first region unmapped? My interpretation of
> vu_add_mem_reg() is that it mmaps duplicate regions to unique mmap_addr
> addresses, so we need to munmap each of them.
I agree - I will remove the found check here.
>
> >
> > - break;
> > + /*
> > + * Shift all affected entries by 1 to close the hole at index i and
> > + * zero out the last entry.
> > + */
> > + memmove(dev->regions + i, dev->regions + i + 1,
> > + sizeof(VuDevRegion) * (dev->nregions - i - 1));
> > + memset(dev->regions + dev->nregions - 1, 0, sizeof(VuDevRegion));
> > + DPRINT("Successfully removed a region\n");
> > + dev->nregions--;
> > +
> > + found = true;
> > }
>
> i-- is missing. dev->regions[] has been shortened so we need to check
> the same element again.
Ack
^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2022-01-06 5:39 UTC | newest]
Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-12-15 22:29 [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
2021-12-15 22:29 ` [RFC 1/5] libvhost-user: Add vu_rem_mem_reg input validation Raphael Norwitz
2022-01-05 11:00 ` Stefan Hajnoczi
2022-01-06 5:13 ` Raphael Norwitz
2021-12-15 22:29 ` [RFC 2/5] libvhost-user: Add vu_add_mem_reg " Raphael Norwitz
2022-01-05 11:02 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 3/5] libvhost-user: Simplify VHOST_USER_REM_MEM_REG Raphael Norwitz
2022-01-05 11:04 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 4/5] libvhost-user: prevent over-running max RAM slots Raphael Norwitz
2022-01-05 11:06 ` Stefan Hajnoczi
2021-12-15 22:29 ` [RFC 5/5] libvhost-user: handle removal of identical regions Raphael Norwitz
2022-01-05 11:18 ` Stefan Hajnoczi
2022-01-06 5:36 ` Raphael Norwitz
2022-01-04 15:46 ` [RFC 0/5] Clean up error handling in libvhost-user memory mapping Raphael Norwitz
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