linux-next: Tree for May 16 (security/landlock/ruleset.c)
Kees Cook
kees at kernel.org
Mon May 19 18:19:53 UTC 2025
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
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