* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
[not found] <20250516202417.31b13d13@canb.auug.org.au>
@ 2025-05-17 2:54 ` Randy Dunlap
2025-05-19 15:29 ` Mickaël Salaün
0 siblings, 1 reply; 12+ messages in thread
From: Randy Dunlap @ 2025-05-17 2:54 UTC (permalink / raw)
To: Stephen Rothwell, Linux Next Mailing List
Cc: Linux Kernel Mailing List, Mickaël Salaün,
linux-security-module, Kees Cook
[-- Attachment #1: Type: text/plain, Size: 1023 bytes --]
On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> Hi all,
>
> Changes since 20250515:
>
on i386:
In file included from ../arch/x86/include/asm/string.h:3,
from ../include/linux/string.h:65,
from ../include/linux/bitmap.h:13,
from ../include/linux/cpumask.h:12,
from ../include/linux/smp.h:13,
from ../include/linux/lockdep.h:14,
from ../security/landlock/ruleset.c:16:
../security/landlock/ruleset.c: In function 'create_rule':
../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
| ^~~~~~~~~~~~~~~~~~~~~~~~~
../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
137 | memcpy(new_rule->layers, layers,
| ^~~~~~
Full randconfig file is attached.
--
~Randy
[-- Attachment #2: config-r9208.gz --]
[-- Type: application/gzip, Size: 28788 bytes --]
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-17 2:54 ` linux-next: Tree for May 16 (security/landlock/ruleset.c) Randy Dunlap
@ 2025-05-19 15:29 ` Mickaël Salaün
2025-05-19 18:19 ` Kees Cook
0 siblings, 1 reply; 12+ messages in thread
From: Mickaël Salaün @ 2025-05-19 15:29 UTC (permalink / raw)
To: Randy Dunlap
Cc: Stephen Rothwell, Linux Next Mailing List,
Linux Kernel Mailing List, linux-security-module, Kees Cook,
Günther Noack
On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
>
>
> On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> > Hi all,
> >
> > Changes since 20250515:
Thanks for the report.
It is the same warning as reported here:
https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
I don't know what the actual issue is though.
>
> on i386:
>
> In file included from ../arch/x86/include/asm/string.h:3,
> from ../include/linux/string.h:65,
> from ../include/linux/bitmap.h:13,
> from ../include/linux/cpumask.h:12,
> from ../include/linux/smp.h:13,
> from ../include/linux/lockdep.h:14,
> from ../security/landlock/ruleset.c:16:
> ../security/landlock/ruleset.c: In function 'create_rule':
> ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~
> ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> 137 | memcpy(new_rule->layers, layers,
> | ^~~~~~
>
>
> Full randconfig file is attached.
>
> --
> ~Randy
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 15:29 ` Mickaël Salaün
@ 2025-05-19 18:19 ` Kees Cook
2025-05-19 18:41 ` Mickaël Salaün
0 siblings, 1 reply; 12+ messages in thread
From: Kees Cook @ 2025-05-19 18:19 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Randy Dunlap, Steven Rostedt, Stephen Rothwell,
Linux Next Mailing List, Linux Kernel Mailing List,
linux-security-module, Günther Noack
On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote:
> On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
> >
> >
> > On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> > > Hi all,
> > >
> > > Changes since 20250515:
>
> Thanks for the report.
>
> It is the same warning as reported here:
> https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
>
> I don't know what the actual issue is though.
>
> >
> > on i386:
> >
> > In file included from ../arch/x86/include/asm/string.h:3,
> > from ../include/linux/string.h:65,
> > from ../include/linux/bitmap.h:13,
> > from ../include/linux/cpumask.h:12,
> > from ../include/linux/smp.h:13,
> > from ../include/linux/lockdep.h:14,
> > from ../security/landlock/ruleset.c:16:
> > ../security/landlock/ruleset.c: In function 'create_rule':
> > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > 137 | memcpy(new_rule->layers, layers,
> > | ^~~~~~
> >
> >
> > Full randconfig file is attached.
The trigger appears to be CONFIG_PROFILE_ALL_BRANCHES, and GCC getting
tricked into thinking check_mul_overflow() returns true:
In file included from ../arch/x86/include/asm/string.h:3,
from ../include/linux/string.h:65,
from ../include/linux/bitmap.h:13,
from ../include/linux/cpumask.h:12,
from ../include/linux/smp.h:13,
from ../include/linux/lockdep.h:14,
from ../security/landlock/ruleset.c:16:
../security/landlock/ruleset.c: In function 'create_rule':
../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 0 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
| ^~~~~~~~~~~~~~~~~~~~~~~~~
../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
137 | memcpy(new_rule->layers, layers,
| ^~~~~~
'create_rule': event 1
../include/linux/compiler.h:69:46:
68 | (cond) ? \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
69 | (__if_trace.miss_hit[1]++,1) : \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
| |
| (1) when the condition is evaluated to true
70 | (__if_trace.miss_hit[0]++,0); \
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../include/linux/compiler.h:57:69: note: in expansion of macro '__trace_if_value'
57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
| ^~~~~~~~~~~~~~~~
../include/linux/compiler.h:55:28: note: in expansion of macro '__trace_if_var'
55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
| ^~~~~~~~~~~~~~
../include/linux/overflow.h:270:9: note: in expansion of macro 'if'
270 | if (check_mul_overflow(factor1, factor2, &bytes))
| ^~
'create_rule': event 2
../arch/x86/include/asm/string_32.h:150:25:
150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
| ^~~~~~~~~~~~~~~~~~~~~~~~~
| |
| (2) out of array bounds here
../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
137 | memcpy(new_rule->layers, layers,
| ^~~~~~
make[1]: Leaving directory '/srv/code/gcc-bug'
I'll take a look at ways to make either the overflow macros or memcpy
robust against this kind of weirdness...
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 18:19 ` Kees Cook
@ 2025-05-19 18:41 ` Mickaël Salaün
2025-05-19 19:15 ` Kees Cook
0 siblings, 1 reply; 12+ messages in thread
From: Mickaël Salaün @ 2025-05-19 18:41 UTC (permalink / raw)
To: Kees Cook
Cc: Randy Dunlap, Steven Rostedt, Stephen Rothwell,
Linux Next Mailing List, Linux Kernel Mailing List,
linux-security-module, Günther Noack
On Mon, May 19, 2025 at 11:19:53AM -0700, Kees Cook wrote:
> On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote:
> > On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
> > >
> > >
> > > On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> > > > Hi all,
> > > >
> > > > Changes since 20250515:
> >
> > Thanks for the report.
> >
> > It is the same warning as reported here:
> > https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> >
> > I don't know what the actual issue is though.
> >
> > >
> > > on i386:
> > >
> > > In file included from ../arch/x86/include/asm/string.h:3,
> > > from ../include/linux/string.h:65,
> > > from ../include/linux/bitmap.h:13,
> > > from ../include/linux/cpumask.h:12,
> > > from ../include/linux/smp.h:13,
> > > from ../include/linux/lockdep.h:14,
> > > from ../security/landlock/ruleset.c:16:
> > > ../security/landlock/ruleset.c: In function 'create_rule':
> > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > 137 | memcpy(new_rule->layers, layers,
> > > | ^~~~~~
> > >
> > >
> > > Full randconfig file is attached.
>
> The trigger appears to be CONFIG_PROFILE_ALL_BRANCHES, and GCC getting
> tricked into thinking check_mul_overflow() returns true:
>
> In file included from ../arch/x86/include/asm/string.h:3,
> from ../include/linux/string.h:65,
> from ../include/linux/bitmap.h:13,
> from ../include/linux/cpumask.h:12,
> from ../include/linux/smp.h:13,
> from ../include/linux/lockdep.h:14,
> from ../security/landlock/ruleset.c:16:
> ../security/landlock/ruleset.c: In function 'create_rule':
> ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 0 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~
> ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> 137 | memcpy(new_rule->layers, layers,
> | ^~~~~~
> 'create_rule': event 1
> ../include/linux/compiler.h:69:46:
> 68 | (cond) ? \
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 69 | (__if_trace.miss_hit[1]++,1) : \
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
> | |
> | (1) when the condition is evaluated to true
> 70 | (__if_trace.miss_hit[0]++,0); \
> | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> ../include/linux/compiler.h:57:69: note: in expansion of macro '__trace_if_value'
> 57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
> | ^~~~~~~~~~~~~~~~
> ../include/linux/compiler.h:55:28: note: in expansion of macro '__trace_if_var'
> 55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
> | ^~~~~~~~~~~~~~
> ../include/linux/overflow.h:270:9: note: in expansion of macro 'if'
> 270 | if (check_mul_overflow(factor1, factor2, &bytes))
> | ^~
> 'create_rule': event 2
> ../arch/x86/include/asm/string_32.h:150:25:
> 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~
> | |
> | (2) out of array bounds here
> ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> 137 | memcpy(new_rule->layers, layers,
> | ^~~~~~
> make[1]: Leaving directory '/srv/code/gcc-bug'
That's interesting...
>
>
> I'll take a look at ways to make either the overflow macros or memcpy
> robust against this kind of weirdness...
Thanks!
>
> --
> Kees Cook
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 18:41 ` Mickaël Salaün
@ 2025-05-19 19:15 ` Kees Cook
2025-05-19 20:26 ` Randy Dunlap
` (2 more replies)
0 siblings, 3 replies; 12+ messages in thread
From: Kees Cook @ 2025-05-19 19:15 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Randy Dunlap, Steven Rostedt, Stephen Rothwell,
Linux Next Mailing List, Linux Kernel Mailing List,
linux-security-module, Günther Noack
On Mon, May 19, 2025 at 08:41:17PM +0200, Mickaël Salaün wrote:
> On Mon, May 19, 2025 at 11:19:53AM -0700, Kees Cook wrote:
> > On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote:
> > > On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
> > > >
> > > >
> > > > On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> > > > > Hi all,
> > > > >
> > > > > Changes since 20250515:
> > >
> > > Thanks for the report.
> > >
> > > It is the same warning as reported here:
> > > https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> > >
> > > I don't know what the actual issue is though.
> > >
> > > >
> > > > on i386:
> > > >
> > > > In file included from ../arch/x86/include/asm/string.h:3,
> > > > from ../include/linux/string.h:65,
> > > > from ../include/linux/bitmap.h:13,
> > > > from ../include/linux/cpumask.h:12,
> > > > from ../include/linux/smp.h:13,
> > > > from ../include/linux/lockdep.h:14,
> > > > from ../security/landlock/ruleset.c:16:
> > > > ../security/landlock/ruleset.c: In function 'create_rule':
> > > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > > 137 | memcpy(new_rule->layers, layers,
> > > > | ^~~~~~
> > > >
> > > >
> > > > Full randconfig file is attached.
> >
> > The trigger appears to be CONFIG_PROFILE_ALL_BRANCHES, and GCC getting
> > tricked into thinking check_mul_overflow() returns true:
> >
> > In file included from ../arch/x86/include/asm/string.h:3,
> > from ../include/linux/string.h:65,
> > from ../include/linux/bitmap.h:13,
> > from ../include/linux/cpumask.h:12,
> > from ../include/linux/smp.h:13,
> > from ../include/linux/lockdep.h:14,
> > from ../security/landlock/ruleset.c:16:
> > ../security/landlock/ruleset.c: In function 'create_rule':
> > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 0 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > 137 | memcpy(new_rule->layers, layers,
> > | ^~~~~~
> > 'create_rule': event 1
> > ../include/linux/compiler.h:69:46:
> > 68 | (cond) ? \
> > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > 69 | (__if_trace.miss_hit[1]++,1) : \
> > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
> > | |
> > | (1) when the condition is evaluated to true
> > 70 | (__if_trace.miss_hit[0]++,0); \
> > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ../include/linux/compiler.h:57:69: note: in expansion of macro '__trace_if_value'
> > 57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
> > | ^~~~~~~~~~~~~~~~
> > ../include/linux/compiler.h:55:28: note: in expansion of macro '__trace_if_var'
> > 55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
> > | ^~~~~~~~~~~~~~
> > ../include/linux/overflow.h:270:9: note: in expansion of macro 'if'
> > 270 | if (check_mul_overflow(factor1, factor2, &bytes))
> > | ^~
> > 'create_rule': event 2
> > ../arch/x86/include/asm/string_32.h:150:25:
> > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > | |
> > | (2) out of array bounds here
> > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > 137 | memcpy(new_rule->layers, layers,
> > | ^~~~~~
> > make[1]: Leaving directory '/srv/code/gcc-bug'
>
> That's interesting...
>
> >
> >
> > I'll take a look at ways to make either the overflow macros or memcpy
> > robust against this kind of weirdness...
>
> Thanks!
I'm doing some build testing, but the below patch makes GCC happy.
Alternatively we could make CONFIG_PROFILE_ALL_BRANCHES=y depend on
CONFIG_FORTIFY_SOURCE=y ...
From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
From: Kees Cook <kees@kernel.org>
Date: Mon, 19 May 2025 11:52:06 -0700
Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Instead of defining memcpy() in terms of __builtin_memcpy() deep
in arch/x86/include/asm/string_32.h, notice that it is needed up in
the general string.h, as done with other common C String APIs. This
allows us to add basic sanity checking for pathological "size"
arguments to memcpy(). Besides the run-time checking benefit, this
avoids GCC trying to be very smart about value range tracking[1] when
CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
Link: https://lore.kernel.org/all/202505191117.C094A90F88@keescook/ [1]
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Closes: https://lore.kernel.org/all/e3754f69-1dea-4542-8de0-a567a14fb95b@infradead.org/
Signed-off-by: Kees Cook <kees@kernel.org>
---
Cc: "Mickaël Salaün" <mic@digikod.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: <x86@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Uros Bizjak <ubizjak@gmail.com>
Cc: <linux-hardening@vger.kernel.org>
---
arch/x86/include/asm/string_32.h | 6 ------
include/linux/string.h | 13 +++++++++++++
2 files changed, 13 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
index e9cce169bb4c..74397c95fa37 100644
--- a/arch/x86/include/asm/string_32.h
+++ b/arch/x86/include/asm/string_32.h
@@ -145,12 +145,6 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
#define __HAVE_ARCH_MEMCPY
extern void *memcpy(void *, const void *, size_t);
-#ifndef CONFIG_FORTIFY_SOURCE
-
-#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
-
-#endif /* !CONFIG_FORTIFY_SOURCE */
-
#define __HAVE_ARCH_MEMMOVE
void *memmove(void *dest, const void *src, size_t n);
diff --git a/include/linux/string.h b/include/linux/string.h
index 01621ad0f598..ffcee31a14f9 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -3,6 +3,7 @@
#define _LINUX_STRING_H_
#include <linux/args.h>
+#include <linux/bug.h>
#include <linux/array_size.h>
#include <linux/cleanup.h> /* for DEFINE_FREE() */
#include <linux/compiler.h> /* for inline */
@@ -390,7 +391,19 @@ static inline const char *kbasename(const char *path)
#if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
#include <linux/fortify-string.h>
+#else
+/* Basic sanity checking even without FORTIFY_SOURCE */
+# ifndef __HAVE_ARCH_MEMCPY
+# define memcpy(t, f, n) \
+ do { \
+ typeof(n) __n = (n); \
+ /* Skip impossible sizes. */ \
+ if (!WARN_ON(__n < 0 || __n == SIZE_MAX)) \
+ __builtin_memcpy(t, f, __n); \
+ } while (0)
+# endif
#endif
+
#ifndef unsafe_memcpy
#define unsafe_memcpy(dst, src, bytes, justification) \
memcpy(dst, src, bytes)
--
2.34.1
--
Kees Cook
^ permalink raw reply related [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 19:15 ` Kees Cook
@ 2025-05-19 20:26 ` Randy Dunlap
2025-05-20 16:44 ` Kees Cook
2025-05-20 14:01 ` Andy Shevchenko
2025-05-20 14:45 ` Mickaël Salaün
2 siblings, 1 reply; 12+ messages in thread
From: Randy Dunlap @ 2025-05-19 20:26 UTC (permalink / raw)
To: Kees Cook, Mickaël Salaün
Cc: Steven Rostedt, Stephen Rothwell, Linux Next Mailing List,
Linux Kernel Mailing List, linux-security-module,
Günther Noack
> From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
> From: Kees Cook <kees@kernel.org>
> Date: Mon, 19 May 2025 11:52:06 -0700
> Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Instead of defining memcpy() in terms of __builtin_memcpy() deep
> in arch/x86/include/asm/string_32.h, notice that it is needed up in
> the general string.h, as done with other common C String APIs. This
> allows us to add basic sanity checking for pathological "size"
> arguments to memcpy(). Besides the run-time checking benefit, this
> avoids GCC trying to be very smart about value range tracking[1] when
> CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
>
> Link: https://lore.kernel.org/all/202505191117.C094A90F88@keescook/ [1]
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Closes: https://lore.kernel.org/all/e3754f69-1dea-4542-8de0-a567a14fb95b@infradead.org/
> Signed-off-by: Kees Cook <kees@kernel.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Thanks.
> ---
> Cc: "Mickaël Salaün" <mic@digikod.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: <x86@kernel.org>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: Uros Bizjak <ubizjak@gmail.com>
> Cc: <linux-hardening@vger.kernel.org>
> ---
> arch/x86/include/asm/string_32.h | 6 ------
> include/linux/string.h | 13 +++++++++++++
> 2 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
> index e9cce169bb4c..74397c95fa37 100644
> --- a/arch/x86/include/asm/string_32.h
> +++ b/arch/x86/include/asm/string_32.h
> @@ -145,12 +145,6 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
> #define __HAVE_ARCH_MEMCPY
> extern void *memcpy(void *, const void *, size_t);
>
> -#ifndef CONFIG_FORTIFY_SOURCE
> -
> -#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> -
> -#endif /* !CONFIG_FORTIFY_SOURCE */
> -
> #define __HAVE_ARCH_MEMMOVE
> void *memmove(void *dest, const void *src, size_t n);
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 01621ad0f598..ffcee31a14f9 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -3,6 +3,7 @@
> #define _LINUX_STRING_H_
>
> #include <linux/args.h>
> +#include <linux/bug.h>
> #include <linux/array_size.h>
> #include <linux/cleanup.h> /* for DEFINE_FREE() */
> #include <linux/compiler.h> /* for inline */
> @@ -390,7 +391,19 @@ static inline const char *kbasename(const char *path)
>
> #if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
> #include <linux/fortify-string.h>
> +#else
> +/* Basic sanity checking even without FORTIFY_SOURCE */
> +# ifndef __HAVE_ARCH_MEMCPY
> +# define memcpy(t, f, n) \
> + do { \
> + typeof(n) __n = (n); \
> + /* Skip impossible sizes. */ \
> + if (!WARN_ON(__n < 0 || __n == SIZE_MAX)) \
> + __builtin_memcpy(t, f, __n); \
> + } while (0)
> +# endif
> #endif
> +
> #ifndef unsafe_memcpy
> #define unsafe_memcpy(dst, src, bytes, justification) \
> memcpy(dst, src, bytes)
--
~Randy
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 19:15 ` Kees Cook
2025-05-19 20:26 ` Randy Dunlap
@ 2025-05-20 14:01 ` Andy Shevchenko
2025-05-20 16:47 ` Kees Cook
2025-05-20 14:45 ` Mickaël Salaün
2 siblings, 1 reply; 12+ messages in thread
From: Andy Shevchenko @ 2025-05-20 14:01 UTC (permalink / raw)
To: Kees Cook
Cc: Mickaël Salaün, Randy Dunlap, Steven Rostedt,
Stephen Rothwell, Linux Next Mailing List,
Linux Kernel Mailing List, linux-security-module,
Günther Noack
On Mon, May 19, 2025 at 12:15:30PM -0700, Kees Cook wrote:
> On Mon, May 19, 2025 at 08:41:17PM +0200, Mickaël Salaün wrote:
...
> >From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
> From: Kees Cook <kees@kernel.org>
> Date: Mon, 19 May 2025 11:52:06 -0700
> Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Instead of defining memcpy() in terms of __builtin_memcpy() deep
> in arch/x86/include/asm/string_32.h, notice that it is needed up in
> the general string.h, as done with other common C String APIs. This
> allows us to add basic sanity checking for pathological "size"
> arguments to memcpy(). Besides the run-time checking benefit, this
> avoids GCC trying to be very smart about value range tracking[1] when
> CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
>
> Link: https://lore.kernel.org/all/202505191117.C094A90F88@keescook/ [1]
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Closes: https://lore.kernel.org/all/e3754f69-1dea-4542-8de0-a567a14fb95b@infradead.org/
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: "Mickaël Salaün" <mic@digikod.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: <x86@kernel.org>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: Uros Bizjak <ubizjak@gmail.com>
> Cc: <linux-hardening@vger.kernel.org>
> ---
> arch/x86/include/asm/string_32.h | 6 ------
> include/linux/string.h | 13 +++++++++++++
> 2 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
> index e9cce169bb4c..74397c95fa37 100644
> --- a/arch/x86/include/asm/string_32.h
> +++ b/arch/x86/include/asm/string_32.h
> @@ -145,12 +145,6 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
> #define __HAVE_ARCH_MEMCPY
> extern void *memcpy(void *, const void *, size_t);
>
> -#ifndef CONFIG_FORTIFY_SOURCE
> -
> -#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> -
> -#endif /* !CONFIG_FORTIFY_SOURCE */
> -
> #define __HAVE_ARCH_MEMMOVE
> void *memmove(void *dest, const void *src, size_t n);
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 01621ad0f598..ffcee31a14f9 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -3,6 +3,7 @@
> #define _LINUX_STRING_H_
>
> #include <linux/args.h>
> +#include <linux/bug.h>
In case you are go with this change, please keep the headers in order.
> #include <linux/array_size.h>
(should be located here)
> #include <linux/cleanup.h> /* for DEFINE_FREE() */
> #include <linux/compiler.h> /* for inline */
> @@ -390,7 +391,19 @@ static inline const char *kbasename(const char *path)
>
> #if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
> #include <linux/fortify-string.h>
> +#else
> +/* Basic sanity checking even without FORTIFY_SOURCE */
> +# ifndef __HAVE_ARCH_MEMCPY
> +# define memcpy(t, f, n) \
> + do { \
> + typeof(n) __n = (n); \
> + /* Skip impossible sizes. */ \
> + if (!WARN_ON(__n < 0 || __n == SIZE_MAX)) \
> + __builtin_memcpy(t, f, __n); \
> + } while (0)
> +# endif
> #endif
> +
> #ifndef unsafe_memcpy
> #define unsafe_memcpy(dst, src, bytes, justification) \
> memcpy(dst, src, bytes)
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 19:15 ` Kees Cook
2025-05-19 20:26 ` Randy Dunlap
2025-05-20 14:01 ` Andy Shevchenko
@ 2025-05-20 14:45 ` Mickaël Salaün
2025-05-20 15:48 ` Randy Dunlap
2025-05-20 16:15 ` Kees Cook
2 siblings, 2 replies; 12+ messages in thread
From: Mickaël Salaün @ 2025-05-20 14:45 UTC (permalink / raw)
To: Kees Cook
Cc: Randy Dunlap, Steven Rostedt, Stephen Rothwell,
Linux Next Mailing List, Linux Kernel Mailing List,
linux-security-module, Günther Noack
On Mon, May 19, 2025 at 12:15:30PM -0700, Kees Cook wrote:
> On Mon, May 19, 2025 at 08:41:17PM +0200, Mickaël Salaün wrote:
> > On Mon, May 19, 2025 at 11:19:53AM -0700, Kees Cook wrote:
> > > On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote:
> > > > On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
> > > > >
> > > > >
> > > > > On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> > > > > > Hi all,
> > > > > >
> > > > > > Changes since 20250515:
> > > >
> > > > Thanks for the report.
> > > >
> > > > It is the same warning as reported here:
> > > > https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> > > >
> > > > I don't know what the actual issue is though.
> > > >
> > > > >
> > > > > on i386:
> > > > >
> > > > > In file included from ../arch/x86/include/asm/string.h:3,
> > > > > from ../include/linux/string.h:65,
> > > > > from ../include/linux/bitmap.h:13,
> > > > > from ../include/linux/cpumask.h:12,
> > > > > from ../include/linux/smp.h:13,
> > > > > from ../include/linux/lockdep.h:14,
> > > > > from ../security/landlock/ruleset.c:16:
> > > > > ../security/landlock/ruleset.c: In function 'create_rule':
> > > > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > > > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > > > 137 | memcpy(new_rule->layers, layers,
> > > > > | ^~~~~~
> > > > >
> > > > >
> > > > > Full randconfig file is attached.
> > >
> > > The trigger appears to be CONFIG_PROFILE_ALL_BRANCHES, and GCC getting
> > > tricked into thinking check_mul_overflow() returns true:
> > >
> > > In file included from ../arch/x86/include/asm/string.h:3,
> > > from ../include/linux/string.h:65,
> > > from ../include/linux/bitmap.h:13,
> > > from ../include/linux/cpumask.h:12,
> > > from ../include/linux/smp.h:13,
> > > from ../include/linux/lockdep.h:14,
> > > from ../security/landlock/ruleset.c:16:
> > > ../security/landlock/ruleset.c: In function 'create_rule':
> > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 0 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > 137 | memcpy(new_rule->layers, layers,
> > > | ^~~~~~
> > > 'create_rule': event 1
> > > ../include/linux/compiler.h:69:46:
> > > 68 | (cond) ? \
> > > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > 69 | (__if_trace.miss_hit[1]++,1) : \
> > > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
> > > | |
> > > | (1) when the condition is evaluated to true
> > > 70 | (__if_trace.miss_hit[0]++,0); \
> > > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > ../include/linux/compiler.h:57:69: note: in expansion of macro '__trace_if_value'
> > > 57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
> > > | ^~~~~~~~~~~~~~~~
> > > ../include/linux/compiler.h:55:28: note: in expansion of macro '__trace_if_var'
> > > 55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
> > > | ^~~~~~~~~~~~~~
> > > ../include/linux/overflow.h:270:9: note: in expansion of macro 'if'
> > > 270 | if (check_mul_overflow(factor1, factor2, &bytes))
> > > | ^~
> > > 'create_rule': event 2
> > > ../arch/x86/include/asm/string_32.h:150:25:
> > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > | |
> > > | (2) out of array bounds here
> > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > 137 | memcpy(new_rule->layers, layers,
> > > | ^~~~~~
> > > make[1]: Leaving directory '/srv/code/gcc-bug'
> >
> > That's interesting...
> >
> > >
> > >
> > > I'll take a look at ways to make either the overflow macros or memcpy
> > > robust against this kind of weirdness...
> >
> > Thanks!
>
> I'm doing some build testing, but the below patch makes GCC happy.
> Alternatively we could make CONFIG_PROFILE_ALL_BRANCHES=y depend on
> CONFIG_FORTIFY_SOURCE=y ...
>
>
> From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
> From: Kees Cook <kees@kernel.org>
> Date: Mon, 19 May 2025 11:52:06 -0700
> Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Instead of defining memcpy() in terms of __builtin_memcpy() deep
> in arch/x86/include/asm/string_32.h, notice that it is needed up in
> the general string.h, as done with other common C String APIs. This
> allows us to add basic sanity checking for pathological "size"
> arguments to memcpy(). Besides the run-time checking benefit, this
> avoids GCC trying to be very smart about value range tracking[1] when
> CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
It works for me but I couldn't reproduce the issue. I tried with
CONFIG_PROFILE_ALL_BRANCHES=y and CONFIG_FORTIFY_SOURCE=n but it always
works without a warning. I'm using GCC 15. Is it specific to a version
of GCC?
>
> Link: https://lore.kernel.org/all/202505191117.C094A90F88@keescook/ [1]
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> Reported-by: Randy Dunlap <rdunlap@infradead.org>
> Closes: https://lore.kernel.org/all/e3754f69-1dea-4542-8de0-a567a14fb95b@infradead.org/
> Signed-off-by: Kees Cook <kees@kernel.org>
> ---
> Cc: "Mickaël Salaün" <mic@digikod.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: <x86@kernel.org>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Andy Shevchenko <andy@kernel.org>
> Cc: Uros Bizjak <ubizjak@gmail.com>
> Cc: <linux-hardening@vger.kernel.org>
> ---
> arch/x86/include/asm/string_32.h | 6 ------
> include/linux/string.h | 13 +++++++++++++
> 2 files changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
> index e9cce169bb4c..74397c95fa37 100644
> --- a/arch/x86/include/asm/string_32.h
> +++ b/arch/x86/include/asm/string_32.h
> @@ -145,12 +145,6 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
> #define __HAVE_ARCH_MEMCPY
> extern void *memcpy(void *, const void *, size_t);
>
> -#ifndef CONFIG_FORTIFY_SOURCE
> -
> -#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> -
> -#endif /* !CONFIG_FORTIFY_SOURCE */
> -
> #define __HAVE_ARCH_MEMMOVE
> void *memmove(void *dest, const void *src, size_t n);
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 01621ad0f598..ffcee31a14f9 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -3,6 +3,7 @@
> #define _LINUX_STRING_H_
>
> #include <linux/args.h>
> +#include <linux/bug.h>
> #include <linux/array_size.h>
> #include <linux/cleanup.h> /* for DEFINE_FREE() */
> #include <linux/compiler.h> /* for inline */
> @@ -390,7 +391,19 @@ static inline const char *kbasename(const char *path)
>
> #if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
> #include <linux/fortify-string.h>
> +#else
> +/* Basic sanity checking even without FORTIFY_SOURCE */
> +# ifndef __HAVE_ARCH_MEMCPY
> +# define memcpy(t, f, n) \
> + do { \
> + typeof(n) __n = (n); \
> + /* Skip impossible sizes. */ \
> + if (!WARN_ON(__n < 0 || __n == SIZE_MAX)) \
> + __builtin_memcpy(t, f, __n); \
> + } while (0)
> +# endif
> #endif
> +
> #ifndef unsafe_memcpy
> #define unsafe_memcpy(dst, src, bytes, justification) \
> memcpy(dst, src, bytes)
> --
> 2.34.1
>
>
>
> --
> Kees Cook
>
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-20 14:45 ` Mickaël Salaün
@ 2025-05-20 15:48 ` Randy Dunlap
2025-05-20 16:15 ` Kees Cook
1 sibling, 0 replies; 12+ messages in thread
From: Randy Dunlap @ 2025-05-20 15:48 UTC (permalink / raw)
To: Mickaël Salaün, Kees Cook
Cc: Steven Rostedt, Stephen Rothwell, Linux Next Mailing List,
Linux Kernel Mailing List, linux-security-module,
Günther Noack
On 5/20/25 7:45 AM, Mickaël Salaün wrote:
> On Mon, May 19, 2025 at 12:15:30PM -0700, Kees Cook wrote:
>> On Mon, May 19, 2025 at 08:41:17PM +0200, Mickaël Salaün wrote:
>>> On Mon, May 19, 2025 at 11:19:53AM -0700, Kees Cook wrote:
>>>> On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote:
>>>>> On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
>>>>>>
>>>>>>
>>>>>> On 5/16/25 3:24 AM, Stephen Rothwell wrote:
>>>>>>> Hi all,
>>>>>>>
>>>>>>> Changes since 20250515:
>>>>>
>>>>> Thanks for the report.
>>>>>
>>>>> It is the same warning as reported here:
>>>>> https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
>>>>>
[snip]
>>>
>>>>
>>>>
>>>> I'll take a look at ways to make either the overflow macros or memcpy
>>>> robust against this kind of weirdness...
>>>
>>> Thanks!
>>
>> I'm doing some build testing, but the below patch makes GCC happy.
>> Alternatively we could make CONFIG_PROFILE_ALL_BRANCHES=y depend on
>> CONFIG_FORTIFY_SOURCE=y ...
>>
>>
>> From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
>> From: Kees Cook <kees@kernel.org>
>> Date: Mon, 19 May 2025 11:52:06 -0700
>> Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
>> MIME-Version: 1.0
>> Content-Type: text/plain; charset=UTF-8
>> Content-Transfer-Encoding: 8bit
>>
>> Instead of defining memcpy() in terms of __builtin_memcpy() deep
>> in arch/x86/include/asm/string_32.h, notice that it is needed up in
>> the general string.h, as done with other common C String APIs. This
>> allows us to add basic sanity checking for pathological "size"
>> arguments to memcpy(). Besides the run-time checking benefit, this
>> avoids GCC trying to be very smart about value range tracking[1] when
>> CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
>
> It works for me but I couldn't reproduce the issue. I tried with
> CONFIG_PROFILE_ALL_BRANCHES=y and CONFIG_FORTIFY_SOURCE=n but it always
> works without a warning. I'm using GCC 15. Is it specific to a version
> of GCC?
I dunno. I'm using GCC 14.2.1.
--
~Randy
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-20 14:45 ` Mickaël Salaün
2025-05-20 15:48 ` Randy Dunlap
@ 2025-05-20 16:15 ` Kees Cook
1 sibling, 0 replies; 12+ messages in thread
From: Kees Cook @ 2025-05-20 16:15 UTC (permalink / raw)
To: Mickaël Salaün
Cc: Randy Dunlap, Steven Rostedt, Stephen Rothwell,
Linux Next Mailing List, Linux Kernel Mailing List,
linux-security-module, Günther Noack
On Tue, May 20, 2025 at 04:45:19PM +0200, Mickaël Salaün wrote:
> On Mon, May 19, 2025 at 12:15:30PM -0700, Kees Cook wrote:
> > On Mon, May 19, 2025 at 08:41:17PM +0200, Mickaël Salaün wrote:
> > > On Mon, May 19, 2025 at 11:19:53AM -0700, Kees Cook wrote:
> > > > On Mon, May 19, 2025 at 05:29:30PM +0200, Mickaël Salaün wrote:
> > > > > On Fri, May 16, 2025 at 07:54:14PM -0700, Randy Dunlap wrote:
> > > > > >
> > > > > >
> > > > > > On 5/16/25 3:24 AM, Stephen Rothwell wrote:
> > > > > > > Hi all,
> > > > > > >
> > > > > > > Changes since 20250515:
> > > > >
> > > > > Thanks for the report.
> > > > >
> > > > > It is the same warning as reported here:
> > > > > https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> > > > >
> > > > > I don't know what the actual issue is though.
> > > > >
> > > > > >
> > > > > > on i386:
> > > > > >
> > > > > > In file included from ../arch/x86/include/asm/string.h:3,
> > > > > > from ../include/linux/string.h:65,
> > > > > > from ../include/linux/bitmap.h:13,
> > > > > > from ../include/linux/cpumask.h:12,
> > > > > > from ../include/linux/smp.h:13,
> > > > > > from ../include/linux/lockdep.h:14,
> > > > > > from ../security/landlock/ruleset.c:16:
> > > > > > ../security/landlock/ruleset.c: In function 'create_rule':
> > > > > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 20 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > > > > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > > > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > > > > 137 | memcpy(new_rule->layers, layers,
> > > > > > | ^~~~~~
> > > > > >
> > > > > >
> > > > > > Full randconfig file is attached.
> > > >
> > > > The trigger appears to be CONFIG_PROFILE_ALL_BRANCHES, and GCC getting
> > > > tricked into thinking check_mul_overflow() returns true:
> > > >
> > > > In file included from ../arch/x86/include/asm/string.h:3,
> > > > from ../include/linux/string.h:65,
> > > > from ../include/linux/bitmap.h:13,
> > > > from ../include/linux/cpumask.h:12,
> > > > from ../include/linux/smp.h:13,
> > > > from ../include/linux/lockdep.h:14,
> > > > from ../security/landlock/ruleset.c:16:
> > > > ../security/landlock/ruleset.c: In function 'create_rule':
> > > > ../arch/x86/include/asm/string_32.h:150:25: warning: '__builtin_memcpy' accessing 4294967295 bytes at offsets 0 and 0 overlaps 6442450943 bytes at offset -2147483648 [-Wrestrict]
> > > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > > 137 | memcpy(new_rule->layers, layers,
> > > > | ^~~~~~
> > > > 'create_rule': event 1
> > > > ../include/linux/compiler.h:69:46:
> > > > 68 | (cond) ? \
> > > > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > 69 | (__if_trace.miss_hit[1]++,1) : \
> > > > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
> > > > | |
> > > > | (1) when the condition is evaluated to true
> > > > 70 | (__if_trace.miss_hit[0]++,0); \
> > > > | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > > > ../include/linux/compiler.h:57:69: note: in expansion of macro '__trace_if_value'
> > > > 57 | #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
> > > > | ^~~~~~~~~~~~~~~~
> > > > ../include/linux/compiler.h:55:28: note: in expansion of macro '__trace_if_var'
> > > > 55 | #define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
> > > > | ^~~~~~~~~~~~~~
> > > > ../include/linux/overflow.h:270:9: note: in expansion of macro 'if'
> > > > 270 | if (check_mul_overflow(factor1, factor2, &bytes))
> > > > | ^~
> > > > 'create_rule': event 2
> > > > ../arch/x86/include/asm/string_32.h:150:25:
> > > > 150 | #define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > > > | ^~~~~~~~~~~~~~~~~~~~~~~~~
> > > > | |
> > > > | (2) out of array bounds here
> > > > ../security/landlock/ruleset.c:137:9: note: in expansion of macro 'memcpy'
> > > > 137 | memcpy(new_rule->layers, layers,
> > > > | ^~~~~~
> > > > make[1]: Leaving directory '/srv/code/gcc-bug'
> > >
> > > That's interesting...
> > >
> > > >
> > > >
> > > > I'll take a look at ways to make either the overflow macros or memcpy
> > > > robust against this kind of weirdness...
> > >
> > > Thanks!
> >
> > I'm doing some build testing, but the below patch makes GCC happy.
> > Alternatively we could make CONFIG_PROFILE_ALL_BRANCHES=y depend on
> > CONFIG_FORTIFY_SOURCE=y ...
> >
> >
> > From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
> > From: Kees Cook <kees@kernel.org>
> > Date: Mon, 19 May 2025 11:52:06 -0700
> > Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
> > MIME-Version: 1.0
> > Content-Type: text/plain; charset=UTF-8
> > Content-Transfer-Encoding: 8bit
> >
> > Instead of defining memcpy() in terms of __builtin_memcpy() deep
> > in arch/x86/include/asm/string_32.h, notice that it is needed up in
> > the general string.h, as done with other common C String APIs. This
> > allows us to add basic sanity checking for pathological "size"
> > arguments to memcpy(). Besides the run-time checking benefit, this
> > avoids GCC trying to be very smart about value range tracking[1] when
> > CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
>
> It works for me but I couldn't reproduce the issue. I tried with
> CONFIG_PROFILE_ALL_BRANCHES=y and CONFIG_FORTIFY_SOURCE=n but it always
> works without a warning. I'm using GCC 15. Is it specific to a version
> of GCC?
It must be more than just those options -- I reproduced it with Randy's
randconfig under GCC 15.
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-19 20:26 ` Randy Dunlap
@ 2025-05-20 16:44 ` Kees Cook
0 siblings, 0 replies; 12+ messages in thread
From: Kees Cook @ 2025-05-20 16:44 UTC (permalink / raw)
To: Randy Dunlap
Cc: Mickaël Salaün, Steven Rostedt, Stephen Rothwell,
Linux Next Mailing List, Linux Kernel Mailing List,
linux-security-module, Günther Noack
On Mon, May 19, 2025 at 01:26:52PM -0700, Randy Dunlap wrote:
>
>
> > From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
> > From: Kees Cook <kees@kernel.org>
> > Date: Mon, 19 May 2025 11:52:06 -0700
> > Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
> > MIME-Version: 1.0
> > Content-Type: text/plain; charset=UTF-8
> > Content-Transfer-Encoding: 8bit
> >
> > Instead of defining memcpy() in terms of __builtin_memcpy() deep
> > in arch/x86/include/asm/string_32.h, notice that it is needed up in
> > the general string.h, as done with other common C String APIs. This
> > allows us to add basic sanity checking for pathological "size"
> > arguments to memcpy(). Besides the run-time checking benefit, this
> > avoids GCC trying to be very smart about value range tracking[1] when
> > CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
> >
> > Link: https://lore.kernel.org/all/202505191117.C094A90F88@keescook/ [1]
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes: https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> > Reported-by: Randy Dunlap <rdunlap@infradead.org>
> > Closes: https://lore.kernel.org/all/e3754f69-1dea-4542-8de0-a567a14fb95b@infradead.org/
> > Signed-off-by: Kees Cook <kees@kernel.org>
>
> Tested-by: Randy Dunlap <rdunlap@infradead.org>
I missed this when I sent out the proper patch. I'll add it locally.
Thanks!
-Kees
>
> Thanks.
>
> > ---
> > Cc: "Mickaël Salaün" <mic@digikod.net>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: <x86@kernel.org>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Andy Shevchenko <andy@kernel.org>
> > Cc: Uros Bizjak <ubizjak@gmail.com>
> > Cc: <linux-hardening@vger.kernel.org>
> > ---
> > arch/x86/include/asm/string_32.h | 6 ------
> > include/linux/string.h | 13 +++++++++++++
> > 2 files changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
> > index e9cce169bb4c..74397c95fa37 100644
> > --- a/arch/x86/include/asm/string_32.h
> > +++ b/arch/x86/include/asm/string_32.h
> > @@ -145,12 +145,6 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
> > #define __HAVE_ARCH_MEMCPY
> > extern void *memcpy(void *, const void *, size_t);
> >
> > -#ifndef CONFIG_FORTIFY_SOURCE
> > -
> > -#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > -
> > -#endif /* !CONFIG_FORTIFY_SOURCE */
> > -
> > #define __HAVE_ARCH_MEMMOVE
> > void *memmove(void *dest, const void *src, size_t n);
> >
> > diff --git a/include/linux/string.h b/include/linux/string.h
> > index 01621ad0f598..ffcee31a14f9 100644
> > --- a/include/linux/string.h
> > +++ b/include/linux/string.h
> > @@ -3,6 +3,7 @@
> > #define _LINUX_STRING_H_
> >
> > #include <linux/args.h>
> > +#include <linux/bug.h>
> > #include <linux/array_size.h>
> > #include <linux/cleanup.h> /* for DEFINE_FREE() */
> > #include <linux/compiler.h> /* for inline */
> > @@ -390,7 +391,19 @@ static inline const char *kbasename(const char *path)
> >
> > #if !defined(__NO_FORTIFY) && defined(__OPTIMIZE__) && defined(CONFIG_FORTIFY_SOURCE)
> > #include <linux/fortify-string.h>
> > +#else
> > +/* Basic sanity checking even without FORTIFY_SOURCE */
> > +# ifndef __HAVE_ARCH_MEMCPY
> > +# define memcpy(t, f, n) \
> > + do { \
> > + typeof(n) __n = (n); \
> > + /* Skip impossible sizes. */ \
> > + if (!WARN_ON(__n < 0 || __n == SIZE_MAX)) \
> > + __builtin_memcpy(t, f, __n); \
> > + } while (0)
> > +# endif
> > #endif
> > +
> > #ifndef unsafe_memcpy
> > #define unsafe_memcpy(dst, src, bytes, justification) \
> > memcpy(dst, src, bytes)
>
> --
> ~Randy
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: linux-next: Tree for May 16 (security/landlock/ruleset.c)
2025-05-20 14:01 ` Andy Shevchenko
@ 2025-05-20 16:47 ` Kees Cook
0 siblings, 0 replies; 12+ messages in thread
From: Kees Cook @ 2025-05-20 16:47 UTC (permalink / raw)
To: Andy Shevchenko
Cc: Mickaël Salaün, Randy Dunlap, Steven Rostedt,
Stephen Rothwell, Linux Next Mailing List,
Linux Kernel Mailing List, linux-security-module,
Günther Noack
On Tue, May 20, 2025 at 05:01:51PM +0300, Andy Shevchenko wrote:
> On Mon, May 19, 2025 at 12:15:30PM -0700, Kees Cook wrote:
> > On Mon, May 19, 2025 at 08:41:17PM +0200, Mickaël Salaün wrote:
>
> ...
>
> > >From 6fbf66fdfd0a7dac809b77faafdd72c60112bb8d Mon Sep 17 00:00:00 2001
> > From: Kees Cook <kees@kernel.org>
> > Date: Mon, 19 May 2025 11:52:06 -0700
> > Subject: [PATCH] string.h: Provide basic sanity checks for fallback memcpy()
> > MIME-Version: 1.0
> > Content-Type: text/plain; charset=UTF-8
> > Content-Transfer-Encoding: 8bit
> >
> > Instead of defining memcpy() in terms of __builtin_memcpy() deep
> > in arch/x86/include/asm/string_32.h, notice that it is needed up in
> > the general string.h, as done with other common C String APIs. This
> > allows us to add basic sanity checking for pathological "size"
> > arguments to memcpy(). Besides the run-time checking benefit, this
> > avoids GCC trying to be very smart about value range tracking[1] when
> > CONFIG_PROFILE_ALL_BRANCHES=y but FORTIFY_SOURCE=n.
> >
> > Link: https://lore.kernel.org/all/202505191117.C094A90F88@keescook/ [1]
> > Reported-by: kernel test robot <lkp@intel.com>
> > Closes: https://lore.kernel.org/all/202501040747.S3LYfvYq-lkp@intel.com/
> > Reported-by: Randy Dunlap <rdunlap@infradead.org>
> > Closes: https://lore.kernel.org/all/e3754f69-1dea-4542-8de0-a567a14fb95b@infradead.org/
> > Signed-off-by: Kees Cook <kees@kernel.org>
> > ---
> > Cc: "Mickaël Salaün" <mic@digikod.net>
> > Cc: Thomas Gleixner <tglx@linutronix.de>
> > Cc: Ingo Molnar <mingo@redhat.com>
> > Cc: Borislav Petkov <bp@alien8.de>
> > Cc: Dave Hansen <dave.hansen@linux.intel.com>
> > Cc: <x86@kernel.org>
> > Cc: "H. Peter Anvin" <hpa@zytor.com>
> > Cc: Andy Shevchenko <andy@kernel.org>
> > Cc: Uros Bizjak <ubizjak@gmail.com>
> > Cc: <linux-hardening@vger.kernel.org>
> > ---
> > arch/x86/include/asm/string_32.h | 6 ------
> > include/linux/string.h | 13 +++++++++++++
> > 2 files changed, 13 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/x86/include/asm/string_32.h b/arch/x86/include/asm/string_32.h
> > index e9cce169bb4c..74397c95fa37 100644
> > --- a/arch/x86/include/asm/string_32.h
> > +++ b/arch/x86/include/asm/string_32.h
> > @@ -145,12 +145,6 @@ static __always_inline void *__constant_memcpy(void *to, const void *from,
> > #define __HAVE_ARCH_MEMCPY
> > extern void *memcpy(void *, const void *, size_t);
> >
> > -#ifndef CONFIG_FORTIFY_SOURCE
> > -
> > -#define memcpy(t, f, n) __builtin_memcpy(t, f, n)
> > -
> > -#endif /* !CONFIG_FORTIFY_SOURCE */
> > -
> > #define __HAVE_ARCH_MEMMOVE
> > void *memmove(void *dest, const void *src, size_t n);
> >
> > diff --git a/include/linux/string.h b/include/linux/string.h
> > index 01621ad0f598..ffcee31a14f9 100644
> > --- a/include/linux/string.h
> > +++ b/include/linux/string.h
> > @@ -3,6 +3,7 @@
> > #define _LINUX_STRING_H_
> >
> > #include <linux/args.h>
> > +#include <linux/bug.h>
>
> In case you are go with this change, please keep the headers in order.
>
> > #include <linux/array_size.h>
>
> (should be located here)
Oops, yes, that was my intent but I typoed my insert, it seems. Fixed
now; thanks!
-Kees
--
Kees Cook
^ permalink raw reply [flat|nested] 12+ messages in thread
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2025-05-17 2:54 ` linux-next: Tree for May 16 (security/landlock/ruleset.c) Randy Dunlap
2025-05-19 15:29 ` Mickaël Salaün
2025-05-19 18:19 ` Kees Cook
2025-05-19 18:41 ` Mickaël Salaün
2025-05-19 19:15 ` Kees Cook
2025-05-19 20:26 ` Randy Dunlap
2025-05-20 16:44 ` Kees Cook
2025-05-20 14:01 ` Andy Shevchenko
2025-05-20 16:47 ` Kees Cook
2025-05-20 14:45 ` Mickaël Salaün
2025-05-20 15:48 ` Randy Dunlap
2025-05-20 16:15 ` Kees Cook
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