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selftests/bpf: Fix array bounds warning in jit_disasm_helpers

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Compiler cannot infer upper bound for labels.cnt and warns about
potential buffer overflow in snprintf. Add an explicit bounds
check (... && i < MAX_LOCAL_LABELS) in the loop condition to fix the
warning.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Ihor Solodrai <ihor.solodrai@linux.dev>
Link: https://lore.kernel.org/r/20260223190736.649171-18-ihor.solodrai@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Ihor Solodrai 2026-02-23 11:07:33 -08:00 • committed by Alexei Starovoitov
parent 2bb270a0ac
commit 3e711c8e47
1 changed files with 9 additions and 9 deletions
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18
tools/testing/selftests/bpf/jit_disasm_helpers.c
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@ -122,15 +122,15 @@ static int disasm_one_func(FILE *text_out, uint8_t *image, __u32 len)
pc += cnt;
}
qsort(labels.pcs, labels.cnt, sizeof(*labels.pcs), cmp_u32);
for (i = 0; i < labels.cnt; ++i)
/* gcc is unable to infer upper bound for labels.cnt and assumes
* it to be U32_MAX. U32_MAX takes 10 decimal digits.
* snprintf below prints into labels.names[*],
* which has space only for two digits and a letter.
* To avoid truncation warning use (i % MAX_LOCAL_LABELS),
* which informs gcc about printed value upper bound.
*/
snprintf(labels.names[i], sizeof(labels.names[i]), "L%d", i % MAX_LOCAL_LABELS);
/* gcc is unable to infer upper bound for labels.cnt and
* assumes it to be U32_MAX. U32_MAX takes 10 decimal digits.
* snprintf below prints into labels.names[*], which has space
* only for two digits and a letter. To avoid truncation
* warning use (i < MAX_LOCAL_LABELS), which informs gcc about
* printed value upper bound.
*/
for (i = 0; i < labels.cnt && i < MAX_LOCAL_LABELS; ++i)
snprintf(labels.names[i], sizeof(labels.names[i]), "L%d", i);
/* now print with labels */
labels.print_phase = true;