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 Signed-off-by: Ihor Solodrai --- .../testing/selftests/bpf/jit_disasm_helpers.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/tools/testing/selftests/bpf/jit_disasm_helpers.c b/tools/testing/selftests/bpf/jit_disasm_helpers.c index febd6b12e372..364c557c5115 100644 --- a/tools/testing/selftests/bpf/jit_disasm_helpers.c +++ b/tools/testing/selftests/bpf/jit_disasm_helpers.c @@ -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; -- 2.53.0