[PATCH 0/4] strict user copy checks on x86_64

[PATCH 0/4] strict user copy checks on x86_64

[Stephen Boyd]

Andrew,

I'm sending this to you because these weren't picked up
last round and the final patch is cross architecture.

Backstory
---------
It turns out that strict user copy checks (also known as
CONFIG_DEBUG_STRICT_USER_COPY_CHECKS) isn't actually implemented
on x86_64 and thus we aren't catching potential security holes
at compile time.

This series adds support for strict user copy checks on x86_64
and silences all the benign warnings in the x86_64 allyesconfig for
linux-next 20110531.

The final patch consolidates the config option as its duplicated
across mutliple arches.

Stephen Boyd (4):
  lpfc: Silence DEBUG_STRICT_USER_COPY_CHECKS=y warning
  kprobes: Silence DEBUG_STRICT_USER_COPY_CHECKS=y warning
  x86: Implement strict user copy checks for x86_64
  Consolidate CONFIG_DEBUG_STRICT_USER_COPY_CHECKS

 arch/parisc/Kconfig               |    1 +
 arch/parisc/Kconfig.debug         |   14 --------------
 arch/s390/Kconfig                 |    1 +
 arch/s390/Kconfig.debug           |   14 --------------
 arch/s390/lib/Makefile            |    1 -
 arch/s390/lib/usercopy.c          |    8 --------
 arch/sparc/lib/Makefile           |    1 -
 arch/sparc/lib/usercopy.c         |    8 --------
 arch/tile/Kconfig                 |    8 +-------
 arch/tile/include/asm/uaccess.h   |    7 ++++++-
 arch/tile/lib/uaccess.c           |    8 --------
 arch/x86/Kconfig                  |    1 +
 arch/x86/Kconfig.debug            |   14 --------------
 arch/x86/include/asm/uaccess_64.h |   12 +++++++++---
 arch/x86/lib/usercopy_32.c        |    6 ------
 drivers/scsi/lpfc/lpfc_debugfs.c  |    3 ++-
 kernel/kprobes.c                  |    2 +-
 lib/Kconfig.debug                 |   18 ++++++++++++++++++
 lib/Makefile                      |    1 +
 lib/usercopy.c                    |    8 ++++++++
 20 files changed, 49 insertions(+), 87 deletions(-)
 delete mode 100644 arch/s390/lib/usercopy.c
 delete mode 100644 arch/sparc/lib/usercopy.c
 create mode 100644 lib/usercopy.c

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

[PATCH 1/4] [SCSI] lpfc: Silence DEBUG_STRICT_USER_COPY_CHECKS=y warning

[Stephen Boyd]

Enabling DEBUG_STRICT_USER_COPY_CHECKS causes the following
warning:

In file included from arch/x86/include/asm/uaccess.h:573,
                 from include/linux/uaccess.h:5,
                 from include/linux/highmem.h:7,
                 from include/linux/pagemap.h:10,
                 from include/linux/blkdev.h:12,
                 from drivers/scsi/lpfc/lpfc_debugfs.c:21:
In function 'copy_from_user':
arch/x86/include/asm/uaccess_64.h:65:
warning: call to 'copy_from_user_overflow' declared with
attribute warning: copy_from_user() buffer size is not provably
correct

presumably due to buf_size being signed causing GCC to fail to
see that buf_size can't become negative.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: James Smart <james.smart@emulex.com>
---
 drivers/scsi/lpfc/lpfc_debugfs.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/scsi/lpfc/lpfc_debugfs.c b/drivers/scsi/lpfc/lpfc_debugfs.c
index ffe82d1..30b25c5 100644
--- a/drivers/scsi/lpfc/lpfc_debugfs.c
+++ b/drivers/scsi/lpfc/lpfc_debugfs.c
@@ -1147,7 +1147,8 @@ static int lpfc_idiag_cmd_get(const char __user *buf, size_t nbytes,
 {
 	char mybuf[64];
 	char *pbuf, *step_str;
-	int bsize, i;
+	int i;
+	size_t bsize;
 
 	/* Protect copy from user */
 	if (!access_ok(VERIFY_READ, buf, nbytes))
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

[PATCH 2/4] kprobes: Silence DEBUG_STRICT_USER_COPY_CHECKS=y warning

[Stephen Boyd]

Enabling DEBUG_STRICT_USER_COPY_CHECKS causes the following
warning:

In file included from arch/x86/include/asm/uaccess.h:573,
                 from kernel/kprobes.c:55:
In function 'copy_from_user',
    inlined from 'write_enabled_file_bool' at
    kernel/kprobes.c:2191:
arch/x86/include/asm/uaccess_64.h:65:
warning: call to 'copy_from_user_overflow' declared with
attribute warning: copy_from_user() buffer size is not provably
correct

presumably due to buf_size being signed causing GCC to fail to
see that buf_size can't become negative.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
 kernel/kprobes.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 7798181..1938187 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2185,7 +2185,7 @@ static ssize_t write_enabled_file_bool(struct file *file,
 	       const char __user *user_buf, size_t count, loff_t *ppos)
 {
 	char buf[32];
-	int buf_size;
+	size_t buf_size;
 
 	buf_size = min(count, (sizeof(buf)-1));
 	if (copy_from_user(buf, user_buf, buf_size))
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

[PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Stephen Boyd]

Strict user copy checks are only really supported on x86_32 even
though the config option is selectable on x86_64. Add the
necessary support to the 64 bit code to trigger copy_from_user()
warnings at compile time.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
---
 arch/x86/include/asm/uaccess_64.h |   12 +++++++++---
 arch/x86/lib/usercopy_64.c        |    6 ++++++
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/uaccess_64.h b/arch/x86/include/asm/uaccess_64.h
index 1c66d30..6ca53e5 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -43,6 +43,14 @@ _copy_from_user(void *to, const void __user *from, unsigned len);
 __must_check unsigned long
 copy_in_user(void __user *to, const void __user *from, unsigned len);
 
+extern void copy_from_user_overflow(void)
+#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
+	__compiletime_error("copy_from_user() buffer size is not provably correct")
+#else
+	__compiletime_warning("copy_from_user() buffer size is not provably correct")
+#endif
+;
+
 static inline unsigned long __must_check copy_from_user(void *to,
 					  const void __user *from,
 					  unsigned long n)
@@ -52,10 +60,8 @@ static inline unsigned long __must_check copy_from_user(void *to,
 	might_fault();
 	if (likely(sz == -1 || sz >= n))
 		n = _copy_from_user(to, from, n);
-#ifdef CONFIG_DEBUG_VM
 	else
-		WARN(1, "Buffer overflow detected!\n");
-#endif
+		copy_from_user_overflow();
 	return n;
 }
 
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index b7c2849..d7a5d9a 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -181,3 +181,9 @@ copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
 			break;
 	return len;
 }
+
+void copy_from_user_overflow(void)
+{
+	WARN(1, "Buffer overflow detected!\n");
+}
+EXPORT_SYMBOL(copy_from_user_overflow);
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

[PATCH 4/4] Consolidate CONFIG_DEBUG_STRICT_USER_COPY_CHECKS

[Stephen Boyd]

The help text for this config is duplicated across the x86,
parisc, and s390 Kconfig.debug files. Arnd Bergman noted that the
help text was slightly misleading and should be fixed to state
that enabling this option isn't a problem when using pre 4.4 gcc.

To simplify the rewording, consolidate the text into
lib/Kconfig.debug and modify it there to be more explicit about
when you should say N to this config.

Also, make the text a bit more generic by stating that this
option enables compile time checks so we can cover architectures
which emit warnings vs. ones which emit errors. The details of
how an architecture decided to implement the checks isn't as
important as the concept of compile time checking of
copy_from_user() calls.

While we're doing this, remove all the copy_from_user_overflow()
code that's duplicated many times and place it into lib/ so that
any architecture supporting this option can get the function for
free.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: linux-parisc@vger.kernel.org
Cc: linux-s390@vger.kernel.org
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
---
 arch/parisc/Kconfig             |    1 +
 arch/parisc/Kconfig.debug       |   14 --------------
 arch/s390/Kconfig               |    1 +
 arch/s390/Kconfig.debug         |   14 --------------
 arch/s390/lib/Makefile          |    1 -
 arch/s390/lib/usercopy.c        |    8 --------
 arch/sparc/lib/Makefile         |    1 -
 arch/sparc/lib/usercopy.c       |    8 --------
 arch/tile/Kconfig               |    8 +-------
 arch/tile/include/asm/uaccess.h |    7 ++++++-
 arch/tile/lib/uaccess.c         |    8 --------
 arch/x86/Kconfig                |    1 +
 arch/x86/Kconfig.debug          |   14 --------------
 arch/x86/lib/usercopy_32.c      |    6 ------
 arch/x86/lib/usercopy_64.c      |    6 ------
 lib/Kconfig.debug               |   18 ++++++++++++++++++
 lib/Makefile                    |    1 +
 lib/usercopy.c                  |    8 ++++++++
 18 files changed, 37 insertions(+), 88 deletions(-)
 delete mode 100644 arch/s390/lib/usercopy.c
 delete mode 100644 arch/sparc/lib/usercopy.c
 create mode 100644 lib/usercopy.c

diff --git a/arch/parisc/Kconfig b/arch/parisc/Kconfig
index 65adc86..3385982 100644
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -15,6 +15,7 @@ config PARISC
 	select HAVE_GENERIC_HARDIRQS
 	select GENERIC_IRQ_PROBE
 	select IRQ_PER_CPU
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 
 	help
 	  The PA-RISC microprocessor is designed by Hewlett-Packard and used
diff --git a/arch/parisc/Kconfig.debug b/arch/parisc/Kconfig.debug
index 7305ac8..bc989e5 100644
--- a/arch/parisc/Kconfig.debug
+++ b/arch/parisc/Kconfig.debug
@@ -12,18 +12,4 @@ config DEBUG_RODATA
          portion of the kernel code won't be covered by a TLB anymore.
          If in doubt, say "N".
 
-config DEBUG_STRICT_USER_COPY_CHECKS
-	bool "Strict copy size checks"
-	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
-	---help---
-	  Enabling this option turns a certain set of sanity checks for user
-	  copy operations into compile time failures.
-
-	  The copy_from_user() etc checks are there to help test if there
-	  are sufficient security checks on the length argument of
-	  the copy operation, by having gcc prove that the argument is
-	  within bounds.
-
-	  If unsure, or if you run an older (pre 4.4) gcc, say N.
-
 endmenu
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 9fab2aa..9726a23 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -117,6 +117,7 @@ config S390
 	select ARCH_INLINE_WRITE_UNLOCK_BH
 	select ARCH_INLINE_WRITE_UNLOCK_IRQ
 	select ARCH_INLINE_WRITE_UNLOCK_IRQRESTORE
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 
 config SCHED_OMIT_FRAME_POINTER
 	def_bool y
diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug
index d76cef3..aa1796c 100644
--- a/arch/s390/Kconfig.debug
+++ b/arch/s390/Kconfig.debug
@@ -17,20 +17,6 @@ config STRICT_DEVMEM
 
 	  If you are unsure, say Y.
 
-config DEBUG_STRICT_USER_COPY_CHECKS
-	def_bool n
-	prompt "Strict user copy size checks"
-	---help---
-	  Enabling this option turns a certain set of sanity checks for user
-	  copy operations into compile time warnings.
-
-	  The copy_from_user() etc checks are there to help test if there
-	  are sufficient security checks on the length argument of
-	  the copy operation, by having gcc prove that the argument is
-	  within bounds.
-
-	  If unsure, or if you run an older (pre 4.4) gcc, say N.
-
 config DEBUG_SET_MODULE_RONX
 	def_bool y
 	depends on MODULES
diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile
index 761ab8b..97975ec 100644
--- a/arch/s390/lib/Makefile
+++ b/arch/s390/lib/Makefile
@@ -3,7 +3,6 @@
 #
 
 lib-y += delay.o string.o uaccess_std.o uaccess_pt.o
-obj-y += usercopy.o
 obj-$(CONFIG_32BIT) += div64.o qrnnd.o ucmpdi2.o
 lib-$(CONFIG_64BIT) += uaccess_mvcos.o
 lib-$(CONFIG_SMP) += spinlock.o
diff --git a/arch/s390/lib/usercopy.c b/arch/s390/lib/usercopy.c
deleted file mode 100644
index 14b363f..0000000
--- a/arch/s390/lib/usercopy.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <linux/module.h>
-#include <linux/bug.h>
-
-void copy_from_user_overflow(void)
-{
-	WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);
diff --git a/arch/sparc/lib/Makefile b/arch/sparc/lib/Makefile
index 7f01b8fc..7747e40 100644
--- a/arch/sparc/lib/Makefile
+++ b/arch/sparc/lib/Makefile
@@ -43,4 +43,3 @@ obj-y                 += iomap.o
 obj-$(CONFIG_SPARC32) += atomic32.o
 obj-y                 += ksyms.o
 obj-$(CONFIG_SPARC64) += PeeCeeI.o
-obj-y                 += usercopy.o
diff --git a/arch/sparc/lib/usercopy.c b/arch/sparc/lib/usercopy.c
deleted file mode 100644
index 14b363f..0000000
--- a/arch/sparc/lib/usercopy.c
+++ /dev/null
@@ -1,8 +0,0 @@
-#include <linux/module.h>
-#include <linux/bug.h>
-
-void copy_from_user_overflow(void)
-{
-	WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);
diff --git a/arch/tile/Kconfig b/arch/tile/Kconfig
index 0249b8b..801fba1 100644
--- a/arch/tile/Kconfig
+++ b/arch/tile/Kconfig
@@ -12,6 +12,7 @@ config TILE
 	select GENERIC_PENDING_IRQ if SMP
 	select GENERIC_IRQ_SHOW
 	select SYS_HYPERVISOR
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 
 # FIXME: investigate whether we need/want these options.
 #	select HAVE_IOREMAP_PROT
@@ -96,13 +97,6 @@ config STRICT_DEVMEM
 config SMP
 	def_bool y
 
-# Allow checking for compile-time determined overflow errors in
-# copy_from_user().  There are still unprovable places in the
-# generic code as of 2.6.34, so this option is not really compatible
-# with -Werror, which is more useful in general.
-config DEBUG_COPY_FROM_USER
-	def_bool n
-
 config HVC_TILE
 	select HVC_DRIVER
 	def_bool y
diff --git a/arch/tile/include/asm/uaccess.h b/arch/tile/include/asm/uaccess.h
index ef34d2c..9a540be 100644
--- a/arch/tile/include/asm/uaccess.h
+++ b/arch/tile/include/asm/uaccess.h
@@ -353,7 +353,12 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
 	return n;
 }
 
-#ifdef CONFIG_DEBUG_COPY_FROM_USER
+#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS
+/*
+ * There are still unprovable places in the generic code as of 2.6.34, so this
+ * option is not really compatible with -Werror, which is more useful in
+ * general.
+ */
 extern void copy_from_user_overflow(void)
 	__compiletime_warning("copy_from_user() size is not provably correct");
 
diff --git a/arch/tile/lib/uaccess.c b/arch/tile/lib/uaccess.c
index f8d398c..030abe3 100644
--- a/arch/tile/lib/uaccess.c
+++ b/arch/tile/lib/uaccess.c
@@ -22,11 +22,3 @@ int __range_ok(unsigned long addr, unsigned long size)
 		 is_arch_mappable_range(addr, size));
 }
 EXPORT_SYMBOL(__range_ok);
-
-#ifdef CONFIG_DEBUG_COPY_FROM_USER
-void copy_from_user_overflow(void)
-{
-       WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);
-#endif
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index da34972..7714ff6 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -70,6 +70,7 @@ config X86
 	select IRQ_FORCED_THREADING
 	select USE_GENERIC_SMP_HELPERS if SMP
 	select HAVE_BPF_JIT if (X86_64 && NET)
+	select ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
 
 config INSTRUCTION_DECODER
 	def_bool (KPROBES || PERF_EVENTS)
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index c0f8a5c..2b00959 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -270,18 +270,4 @@ config OPTIMIZE_INLINING
 
 	  If unsure, say N.
 
-config DEBUG_STRICT_USER_COPY_CHECKS
-	bool "Strict copy size checks"
-	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
-	---help---
-	  Enabling this option turns a certain set of sanity checks for user
-	  copy operations into compile time failures.
-
-	  The copy_from_user() etc checks are there to help test if there
-	  are sufficient security checks on the length argument of
-	  the copy operation, by having gcc prove that the argument is
-	  within bounds.
-
-	  If unsure, or if you run an older (pre 4.4) gcc, say N.
-
 endmenu
diff --git a/arch/x86/lib/usercopy_32.c b/arch/x86/lib/usercopy_32.c
index e218d5d..8498684 100644
--- a/arch/x86/lib/usercopy_32.c
+++ b/arch/x86/lib/usercopy_32.c
@@ -883,9 +883,3 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
 	return n;
 }
 EXPORT_SYMBOL(_copy_from_user);
-
-void copy_from_user_overflow(void)
-{
-	WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);
diff --git a/arch/x86/lib/usercopy_64.c b/arch/x86/lib/usercopy_64.c
index d7a5d9a..b7c2849 100644
--- a/arch/x86/lib/usercopy_64.c
+++ b/arch/x86/lib/usercopy_64.c
@@ -181,9 +181,3 @@ copy_user_handle_tail(char *to, char *from, unsigned len, unsigned zerorest)
 			break;
 	return len;
 }
-
-void copy_from_user_overflow(void)
-{
-	WARN(1, "Buffer overflow detected!\n");
-}
-EXPORT_SYMBOL(copy_from_user_overflow);
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 28afa4c..3298385 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1106,6 +1106,24 @@ config SYSCTL_SYSCALL_CHECK
 	  to properly maintain and use. This enables checks that help
 	  you to keep things correct.
 
+config ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
+	bool
+
+config DEBUG_STRICT_USER_COPY_CHECKS
+	bool "Strict user copy size checks"
+	depends on ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS
+	depends on DEBUG_KERNEL && !TRACE_BRANCH_PROFILING
+	help
+	  Enabling this option turns a certain set of sanity checks for user
+	  copy operations into compile time failures.
+
+	  The copy_from_user() etc checks are there to help test if there
+	  are sufficient security checks on the length argument of
+	  the copy operation, by having gcc prove that the argument is
+	  within bounds.
+
+	  If unsure, say N.
+
 source mm/Kconfig.debug
 source kernel/trace/Kconfig
 
diff --git a/lib/Makefile b/lib/Makefile
index 6b597fd..8195c5e 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -14,6 +14,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 proportions.o prio_heap.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o find_next_bit.o
 
+lib-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
 
diff --git a/lib/usercopy.c b/lib/usercopy.c
new file mode 100644
index 0000000..14b363f
--- /dev/null
+++ b/lib/usercopy.c
@@ -0,0 +1,8 @@
+#include <linux/module.h>
+#include <linux/bug.h>
+
+void copy_from_user_overflow(void)
+{
+	WARN(1, "Buffer overflow detected!\n");
+}
+EXPORT_SYMBOL(copy_from_user_overflow);
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

Re: [PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Andrew Morton]

On Tue, 31 May 2011 11:14:32 -0700
Stephen Boyd <sboyd@codeaurora.org> wrote:

> Strict user copy checks are only really supported on x86_32 even
> though the config option is selectable on x86_64. Add the
> necessary support to the 64 bit code to trigger copy_from_user()
> warnings at compile time.

So I'm getting 20-30 warnings from an x86_64 allmodconfig build.

I don't think we want a million other people to have to put up with
those warnings too.  Can you please take a look at fixing these up?

Re: [PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Stephen Boyd]

On 06/30/2011 12:19 PM, Andrew Morton wrote:
> On Tue, 31 May 2011 11:14:32 -0700
> Stephen Boyd <sboyd@codeaurora.org> wrote:
>
>> Strict user copy checks are only really supported on x86_32 even
>> though the config option is selectable on x86_64. Add the
>> necessary support to the 64 bit code to trigger copy_from_user()
>> warnings at compile time.
>
> So I'm getting 20-30 warnings from an x86_64 allmodconfig build.
>
> I don't think we want a million other people to have to put up with
> those warnings too.  Can you please take a look at fixing these up?
>

Care to share the warnings? I'll run a build again and fix any new
warnings I find.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

Re: [PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Andrew Morton]

On Thu, 30 Jun 2011 12:23:56 -0700
Stephen Boyd <sboyd@codeaurora.org> wrote:

> On 06/30/2011 12:19 PM, Andrew Morton wrote:
> > On Tue, 31 May 2011 11:14:32 -0700
> > Stephen Boyd <sboyd@codeaurora.org> wrote:
> >
> >> Strict user copy checks are only really supported on x86_32 even
> >> though the config option is selectable on x86_64. Add the
> >> necessary support to the 64 bit code to trigger copy_from_user()
> >> warnings at compile time.
> >
> > So I'm getting 20-30 warnings from an x86_64 allmodconfig build.
> >
> > I don't think we want a million other people to have to put up with
> > those warnings too.  Can you please take a look at fixing these up?
> >
> 
> Care to share the warnings? I'll run a build again and fix any new
> warnings I find.


init/calibrate.c: In function 'calibrate_delay':
init/calibrate.c:251: warning: 'lpj' may be used uninitialized in this function
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from include/linux/uaccess.h:5,
                 from include/linux/highmem.h:7,
                 from include/linux/pagemap.h:10,
                 from include/linux/mempolicy.h:70,
                 from mm/mempolicy.c:68:
In function 'copy_from_user',
    inlined from 'compat_sys_get_mempolicy' at mm/mempolicy.c:1415:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
crypto/anubis.c: In function 'anubis_crypt':
crypto/anubis.c:581: warning: 'inter' is used uninitialized in this function
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from include/drm/drmP.h:65,
                 from drivers/gpu/drm/radeon/radeon_state.c:30:
In function 'copy_from_user',
    inlined from 'radeon_cp_clear' at drivers/gpu/drm/radeon/radeon_state.c:2171:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In file included from drivers/message/i2o/config-osm.c:39:
drivers/message/i2o/i2o_config.c: In function 'i2o_cfg_passthru':
drivers/message/i2o/i2o_config.c:881: warning: cast to pointer from integer of different size
drivers/message/i2o/i2o_config.c:936: warning: cast to pointer from integer of different size
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from drivers/message/i2o/config-osm.c:22:
In function 'copy_from_user',
    inlined from 'i2o_cfg_passthru32' at drivers/message/i2o/i2o_config.c:684:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'i2o_cfg_passthru' at drivers/message/i2o/i2o_config.c:919:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from /usr/src/devel/arch/x86/include/asm/sections.h:5,
                 from /usr/src/devel/arch/x86/include/asm/hw_irq.h:26,
                 from include/linux/irq.h:351,
                 from /usr/src/devel/arch/x86/include/asm/hardirq.h:5,
                 from include/linux/hardirq.h:7,
                 from include/linux/interrupt.h:12,
                 from net/core/pktgen.c:135:
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:877:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1145:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1252:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1274:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1298:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1321:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1344:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1365:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1386:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1407:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1429:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1446:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_thread_write' at net/core/pktgen.c:1769:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_thread_write' at net/core/pktgen.c:1800:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from include/net/checksum.h:25,
                 from include/linux/skbuff.h:28,
                 from include/linux/icmpv6.h:82,
                 from net/compat.c:19:
In function 'copy_from_user',
    inlined from 'compat_sys_socketcall' at net/compat.c:792:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
drivers/net/pcmcia/nmclan_cs.c: In function 'nmclan_config':
drivers/net/pcmcia/nmclan_cs.c:628: warning: 'pcmcia_request_exclusive_irq' is deprecated (declared at include/pcmcia/ds.h:201)
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from include/linux/poll.h:14,
                 from drivers/scsi/sg.c:44:
In function 'copy_from_user',
    inlined from 'sg_proc_write_dressz' at drivers/scsi/sg.c:2399:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'sg_proc_write_adio' at drivers/scsi/sg.c:2376:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
                 from include/linux/poll.h:14,
                 from drivers/net/tun.c:49:
In function 'copy_from_user',
    inlined from '__tun_chr_ioctl' at drivers/net/tun.c:1246:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct

Re: [PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Stephen Boyd]

On 6/30/2011 12:36 PM, Andrew Morton wrote:
> On Thu, 30 Jun 2011 12:23:56 -0700
> Stephen Boyd <sboyd@codeaurora.org> wrote:
>
>> Care to share the warnings? I'll run a build again and fix any new
>> warnings I find.

I only get one warning

In file included from /local/mnt2/workspace2/android/kernel/arch/x86/include/asm/uaccess.h:572,  
                 from /local/mnt2/workspace2/android/kernel/include/linux/uaccess.h:5,
                 from /local/mnt2/workspace2/android/kernel/drivers/staging/speakup/devsynth.c:4:
In function 'copy_from_user',
    inlined from 'speakup_file_write' at /local/mnt2/workspace2/android/kernel/drivers/staging/speakup/devsynth.c:28:
/local/mnt2/workspace2/android/kernel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct


But that's probably due to my compiler's age more than anything else
(and it seems you fixed it last Friday).

I did notice that I need to do an obj-y instead of a lib-y in the
Makefile. Can you please squash this into the patch titled
"consolidate-config_debug_strict_user_copy_checks.patch"?

----8<----->8------

diff --git a/lib/Makefile b/lib/Makefile
index 785f9b0..9ca779a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -14,7 +14,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
         proportions.o prio_heap.o ratelimit.o show_mem.o \
         is_single_threaded.o plist.o decompress.o find_next_bit.o
 
-lib-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
+obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
 


> In file included from /usr/src/devel/arch/x86/include/asm/uaccess.h:572,
>                  from include/linux/uaccess.h:5,
>                  from include/linux/highmem.h:7,
>                  from include/linux/pagemap.h:10,
>                  from include/linux/mempolicy.h:70,
>                  from mm/mempolicy.c:68:
>
[snip]
> In function 'copy_from_user',
>     inlined from '__tun_chr_ioctl' at drivers/net/tun.c:1246:
> /usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
>

Does this help at all?

-----8<------->8-------

diff --git a/drivers/gpu/drm/radeon/radeon_state.c b/drivers/gpu/drm/radeon/radeon_state.c
index 92e7ea7..5c8f53c 100644
--- a/drivers/gpu/drm/radeon/radeon_state.c
+++ b/drivers/gpu/drm/radeon/radeon_state.c
@@ -2169,7 +2169,7 @@ static int radeon_cp_clear(struct drm_device *dev, void *data, struct drm_file *
 		sarea_priv->nbox = RADEON_NR_SAREA_CLIPRECTS;
 
 	if (DRM_COPY_FROM_USER(&depth_boxes, clear->depth_boxes,
-			       sarea_priv->nbox * sizeof(depth_boxes[0])))
+			       (size_t)sarea_priv->nbox * sizeof(depth_boxes[0])))
 		return -EFAULT;
 
 	radeon_cp_dispatch_clear(dev, file_priv->master, clear, depth_boxes);
diff --git a/drivers/message/i2o/i2o_config.c b/drivers/message/i2o/i2o_config.c
index 098de2b..4dcdc3d 100644
--- a/drivers/message/i2o/i2o_config.c
+++ b/drivers/message/i2o/i2o_config.c
@@ -680,6 +680,10 @@ static int i2o_cfg_passthru32(struct file *file, unsigned cmnd,
 		}
 		size = size >> 16;
 		size *= 4;
+		if (size > sizeof(rmsg)) {
+			rcode = -EINVAL;
+			goto sg_list_cleanup;
+		}
 		/* Copy in the user's I2O command */
 		if (copy_from_user(rmsg, user_msg, size)) {
 			rcode = -EFAULT;
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 909ed9e..ce76d0c 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -2367,16 +2367,15 @@ static ssize_t
 sg_proc_write_adio(struct file *filp, const char __user *buffer,
 		   size_t count, loff_t *off)
 {
-	int num;
-	char buff[11];
+	int err;
+	unsigned long num;
 
 	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
 		return -EACCES;
-	num = (count < 10) ? count : 10;
-	if (copy_from_user(buff, buffer, num))
-		return -EFAULT;
-	buff[num] = '\0';
-	sg_allow_dio = simple_strtoul(buff, NULL, 10) ? 1 : 0;
+	err = kstrtoul_from_user(buffer, count, 0, &num);
+	if (err)
+		return err;
+	sg_allow_dio = num ? 1 : 0;
 	return count;
 }
 
@@ -2389,17 +2388,15 @@ static ssize_t
 sg_proc_write_dressz(struct file *filp, const char __user *buffer,
 		     size_t count, loff_t *off)
 {
-	int num;
+	int err;
 	unsigned long k = ULONG_MAX;
-	char buff[11];
 
 	if (!capable(CAP_SYS_ADMIN) || !capable(CAP_SYS_RAWIO))
 		return -EACCES;
-	num = (count < 10) ? count : 10;
-	if (copy_from_user(buff, buffer, num))
-		return -EFAULT;
-	buff[num] = '\0';
-	k = simple_strtoul(buff, NULL, 10);
+
+	err = kstrtoul_from_user(buffer, count, 0, &k);
+	if (err)
+		return err;
 	if (k <= 1048576) {	/* limit "big buff" to 1 MB */
 		sg_big_buff = k;
 		return count;
diff --git a/lib/Makefile b/lib/Makefile
index 785f9b0..9ca779a 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -14,7 +14,7 @@ lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 proportions.o prio_heap.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o find_next_bit.o
 
-lib-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
+obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o
 lib-$(CONFIG_MMU) += ioremap.o
 lib-$(CONFIG_SMP) += cpumask.o
 
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index e7fb9d2..e9d4987 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -1405,8 +1405,14 @@ asmlinkage long compat_sys_get_mempolicy(int __user *policy,
 	nr_bits = min_t(unsigned long, maxnode-1, MAX_NUMNODES);
 	alloc_size = ALIGN(nr_bits, BITS_PER_LONG) / 8;
 
-	if (nmask)
+	if (alloc_size > sizeof(bm))
+		return -EINVAL;
+
+	if (nmask) {
 		nm = compat_alloc_user_space(alloc_size);
+		if (!nm)
+			return -ENOMEM;
+	}
 
 	err = sys_get_mempolicy(policy, nm, nr_bits+1, addr, flags);
 
diff --git a/net/compat.c b/net/compat.c
index c578d93..b769233 100644
--- a/net/compat.c
+++ b/net/compat.c
@@ -789,6 +789,8 @@ asmlinkage long compat_sys_socketcall(int call, u32 __user *args)
 
 	if (call < SYS_SOCKET || call > SYS_SENDMMSG)
 		return -EINVAL;
+	if (nas[call] > sizeof(a))
+		return -EINVAL;
 	if (copy_from_user(a, args, nas[call]))
 		return -EFAULT;
 	a0 = a[0];
diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index f76079c..2f4ea06 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c
@@ -1382,6 +1382,8 @@ static ssize_t pktgen_if_write(struct file *file,
 		len = strn_len(&user_buffer[i], sizeof(pkt_dev->src_min) - 1);
 		if (len < 0)
 			return len;
+		if (len > sizeof(buf))
+			return -EINVAL;
 
 		if (copy_from_user(buf, &user_buffer[i], len))
 			return -EFAULT;



-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

Re: [PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Andrew Morton]

On Tue, 31 May 2011 11:14:32 -0700
Stephen Boyd <sboyd@codeaurora.org> wrote:

> Strict user copy checks are only really supported on x86_32 even
> though the config option is selectable on x86_64. Add the
> necessary support to the 64 bit code to trigger copy_from_user()
> warnings at compile time.

I'm still reluctant to go and throw a pile of warnings into many
people's faces without having made an attempt to fix them.


We get a screen full of these:

    inlined from 'pktgen_if_write' at net/core/pktgen.c:877:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
    inlined from 'pktgen_if_write' at net/core/pktgen.c:1145:
/usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
In function 'copy_from_user',
...

and I don't immediately see a way of suppressing them without adding
additional code.

Ideas?

Re: [PATCH 3/4] x86: Implement strict user copy checks for x86_64

[Stephen Boyd]

On 07/07/2011 02:54 PM, Andrew Morton wrote:
> On Tue, 31 May 2011 11:14:32 -0700
> Stephen Boyd <sboyd@codeaurora.org> wrote:
>
>> Strict user copy checks are only really supported on x86_32 even
>> though the config option is selectable on x86_64. Add the
>> necessary support to the 64 bit code to trigger copy_from_user()
>> warnings at compile time.
>
> I'm still reluctant to go and throw a pile of warnings into many
> people's faces without having made an attempt to fix them.
>
>

I agree.

> We get a screen full of these:
>
>     inlined from 'pktgen_if_write' at net/core/pktgen.c:877:
> /usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
> In function 'copy_from_user',
>     inlined from 'pktgen_if_write' at net/core/pktgen.c:1145:
> /usr/src/devel/arch/x86/include/asm/uaccess_64.h:64: warning: call to 'copy_from_user_overflow' declared with attribute warning: copy_from_user() buffer size is not provably correct
> In function 'copy_from_user',
> ...
>
> and I don't immediately see a way of suppressing them without adding
> additional code.
>
> Ideas?

I think your compiler is newer than mine. I tried the 4.6.0 compilers
from kernel.org and only got the mempolicy warning. Ugh. When I sent the
series I was using a 4.4.1 gcc.

What happens if you inline strn_len()? I believe gcc can't prove to
itself that the function returns an int that is always less than the
size of f (or buf). This in turn requires it to generate the code for a
buffer overflow possibility (even though we can tell its never possible).

That's the thing with these strict user copy checks. First off we're
relying on aggressive dead code optimization. Second, the compiler can
easily get confused about constraints when function calls aren't
inlined. I'm tempted to say we should rewrite it from

                char f[32];
                memset(f, 0, 32);
                len = strn_len(&user_buffer[i], sizeof(f) - 1);
                if (len < 0)   
                        return len;

                if (copy_from_user(f, &user_buffer[i], len))


to

                int len = strn_len(&user_buffer[i], 31);
                char f[len + 1];
                memset(f, 0, sizeof(f));
                if (len < 0)   
                        return len;

                if (copy_from_user(f, &user_buffer[i], len))


so that gcc can easily see that f is always 1 more than len. But I can't
convince myself that is better (and it's actually broken with regards to
negative return values but you get the idea).

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.