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bpf/helpers: bpf_strnstr: Exact match length #5843

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bpf/helpers: bpf_strnstr: Exact match length #5843

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d84885c
bpf/helpers: bpf_strnstr: Exact match length
Rtoax Aug 28, 2025
818b8cf
selftests/bpf: Add tests for bpf_strnstr
Rtoax Aug 28, 2025
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4 changes: 3 additions & 1 deletion kernel/bpf/helpers.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3672,10 +3672,12 @@ __bpf_kfunc int bpf_strnstr(const char *s1__ign, const char *s2__ign, size_t len

guard(pagefault)();
for (i = 0; i < XATTR_SIZE_MAX; i++) {
for (j = 0; i + j < len && j < XATTR_SIZE_MAX; j++) {
for (j = 0; i + j <= len && j < XATTR_SIZE_MAX; j++) {
__get_kernel_nofault(&c2, s2__ign + j, char, err_out);
if (c2 == '\0')
return i;
if (i + j == len)
break;
__get_kernel_nofault(&c1, s1__ign + j, char, err_out);
if (c1 == '\0')
return -ENOENT;
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2 changes: 2 additions & 0 deletions tools/testing/selftests/bpf/progs/string_kfuncs_success.c
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Expand Up @@ -30,6 +30,8 @@ __test(2) int test_strcspn(void *ctx) { return bpf_strcspn(str, "lo"); }
__test(6) int test_strstr_found(void *ctx) { return bpf_strstr(str, "world"); }
__test(-ENOENT) int test_strstr_notfound(void *ctx) { return bpf_strstr(str, "hi"); }
__test(0) int test_strstr_empty(void *ctx) { return bpf_strstr(str, ""); }
__test(0) int test_strnstr_found(void *ctx) { return bpf_strnstr("", "", 0); }
__test(0) int test_strnstr_found(void *ctx) { return bpf_strnstr(str, "hello", 5); }
__test(0) int test_strnstr_found(void *ctx) { return bpf_strnstr(str, "hello", 6); }
__test(-ENOENT) int test_strnstr_notfound(void *ctx) { return bpf_strnstr(str, "hi", 10); }
__test(0) int test_strnstr_empty(void *ctx) { return bpf_strnstr(str, "", 1); }
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