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When building ARCH=riscv using clang with CONFIG_FORTIFY_SOURCE and
CONFIG_UBSAN_BOUNDS enabled, CONFIG_NR_CPUS > 64, and the default value of
2 for CONFIG_NODES_SHIFT, there is a compiletime warning from the fortify
routines.
In file included from mm/arch_numa.c:11:
In file included from include/linux/acpi.h:14:
In file included from include/linux/resource_ext.h:11:
In file included from include/linux/slab.h:17:
In file included from include/linux/gfp.h:7:
In file included from include/linux/mmzone.h:8:
In file included from include/linux/spinlock.h:60:
In file included from include/linux/interrupt_rc.h:17:
In file included from include/linux/smp.h:13:
In file included from include/linux/cpumask.h:11:
In file included from include/linux/bitmap.h:13:
In file included from include/linux/string.h:383:
include/linux/fortify-string.h:430:4: warning: call to '__write_overflow_field' declared with 'warning' attribute: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Wattribue-warning]
430 | __write_overflow_field(p_size_field, size);
| ^
include/linux/fortify-string.h:430:4: note: called by function 'fortify_memset_chk(unsigned long, unsigned long, unsigned long)'
include/linux/bitmap.h:248:3: note: inlined by function 'setup_node_to_cpumask_map'
248 | memset(dst, 0, len);
| ^
include/linux/fortify-string.h:462:25: note: expanded from macro 'memset'
462 | #define memset(p, c, s) __fortify_memset_chk(p, c, s, \
| ^
include/linux/fortify-string.h:453:2: note: expanded from macro '__fortify_memset_chk'
453 | fortify_memset_chk(__fortify_size, p_size, p_size_field), \
| ^
include/linux/fortify-string.h:430:4: note: use '-gline-directives-only' (implied by '-g1') or higher for more accurate inlining chain locations
430 | __write_overflow_field(p_size_field, size);
| ^
1 warning generated.
In this configuration, MAX_NUMNODES is 4. clang unrolls the for loop in
setup_node_to_cpumask_map() past this, which triggers the fortify check
when accessing node_to_cpumask_map on the theoretical fifth loop iteration
because it would be an out of bounds write.
Make it clear to clang that nr_node_ids is bounded by MAX_NUMNODES due to
the logic in setup_nr_node_ids() by early returning in
setup_node_to_cpumask_map() should that condition be violated.
Link: https://lore.kernel.org/20260813-arch_numa-avoid-fortify-warning-v2-1-093ad97a78df@kernel.org
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Closes: https://github.com/ClangBuiltLinux/linux/issues/2174
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Kees Cook <kees@kernel.org>
Cc: Bill Wendling <morbo@google.com>
Cc: Justin Stitt <justinstitt@google.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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