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bpf: add bpf_strcasestr,bpf_strncasestr kfuncs #6096

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6ce2a46
bpf: add bpf_strcasestr,bpf_strncasestr kfuncs
Rtoax Oct 4, 2025
0733909
selftests/bpf: Test bpf_strcasestr,bpf_strncasestr kfuncs
Rtoax Oct 4, 2025
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96 changes: 75 additions & 21 deletions kernel/bpf/helpers.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3675,34 +3675,20 @@ __bpf_kfunc int bpf_strcspn(const char *s__ign, const char *reject__ign)
return -EFAULT;
}

/**
* bpf_strnstr - Find the first substring in a length-limited string
* @s1__ign: The string to be searched
* @s2__ign: The string to search for
* @len: the maximum number of characters to search
*
* Return:
* * >=0 - Index of the first character of the first occurrence of @s2__ign
* within the first @len characters of @s1__ign
* * %-ENOENT - @s2__ign not found in the first @len characters of @s1__ign
* * %-EFAULT - Cannot read one of the strings
* * %-E2BIG - One of the strings is too large
* * %-ERANGE - One of the strings is outside of kernel address space
*/
__bpf_kfunc int bpf_strnstr(const char *s1__ign, const char *s2__ign, size_t len)
int __bpf_strnstr(const char *s1, const char *s2, size_t len, bool ignore_case)
{
char c1, c2;
int i, j;

if (!copy_from_kernel_nofault_allowed(s1__ign, 1) ||
!copy_from_kernel_nofault_allowed(s2__ign, 1)) {
if (!copy_from_kernel_nofault_allowed(s1, 1) ||
!copy_from_kernel_nofault_allowed(s2, 1)) {
return -ERANGE;
}

guard(pagefault)();
for (i = 0; i < XATTR_SIZE_MAX; i++) {
for (j = 0; i + j <= len && j < XATTR_SIZE_MAX; j++) {
__get_kernel_nofault(&c2, s2__ign + j, char, err_out);
__get_kernel_nofault(&c2, s2 + j, char, err_out);
if (c2 == '\0')
return i;
/*
Expand All @@ -3712,7 +3698,13 @@ __bpf_kfunc int bpf_strnstr(const char *s1__ign, const char *s2__ign, size_t len
*/
if (i + j == len)
break;
__get_kernel_nofault(&c1, s1__ign + j, char, err_out);
__get_kernel_nofault(&c1, s1 + j, char, err_out);

if (ignore_case) {
c1 = tolower(c1);
c2 = tolower(c2);
}

if (c1 == '\0')
return -ENOENT;
if (c1 != c2)
Expand All @@ -3722,7 +3714,7 @@ __bpf_kfunc int bpf_strnstr(const char *s1__ign, const char *s2__ign, size_t len
return -E2BIG;
if (i + j == len)
return -ENOENT;
s1__ign++;
s1++;
}
return -E2BIG;
err_out:
Expand All @@ -3744,8 +3736,68 @@ __bpf_kfunc int bpf_strnstr(const char *s1__ign, const char *s2__ign, size_t len
*/
__bpf_kfunc int bpf_strstr(const char *s1__ign, const char *s2__ign)
{
return bpf_strnstr(s1__ign, s2__ign, XATTR_SIZE_MAX);
return __bpf_strnstr(s1__ign, s2__ign, XATTR_SIZE_MAX, false);
}

/**
* bpf_strcasestr - Find the first substring in a string, ignoring the case of
* the characters
* @s1__ign: The string to be searched
* @s2__ign: The string to search for
*
* Return:
* * >=0 - Index of the first character of the first occurrence of @s2__ign
* within @s1__ign
* * %-ENOENT - @s2__ign is not a substring of @s1__ign
* * %-EFAULT - Cannot read one of the strings
* * %-E2BIG - One of the strings is too large
* * %-ERANGE - One of the strings is outside of kernel address space
*/
__bpf_kfunc int bpf_strcasestr(const char *s1__ign, const char *s2__ign)
{
return __bpf_strnstr(s1__ign, s2__ign, XATTR_SIZE_MAX, true);
}

/**
* bpf_strnstr - Find the first substring in a length-limited string
* @s1__ign: The string to be searched
* @s2__ign: The string to search for
* @len: the maximum number of characters to search
*
* Return:
* * >=0 - Index of the first character of the first occurrence of @s2__ign
* within the first @len characters of @s1__ign
* * %-ENOENT - @s2__ign not found in the first @len characters of @s1__ign
* * %-EFAULT - Cannot read one of the strings
* * %-E2BIG - One of the strings is too large
* * %-ERANGE - One of the strings is outside of kernel address space
*/
__bpf_kfunc int bpf_strnstr(const char *s1__ign, const char *s2__ign, size_t len)
{
return __bpf_strnstr(s1__ign, s2__ign, len, false);
}

/**
* bpf_strnstr - Find the first substring in a length-limited string, ignoring
* the case of the characters
* @s1__ign: The string to be searched
* @s2__ign: The string to search for
* @len: the maximum number of characters to search
*
* Return:
* * >=0 - Index of the first character of the first occurrence of @s2__ign
* within the first @len characters of @s1__ign
* * %-ENOENT - @s2__ign not found in the first @len characters of @s1__ign
* * %-EFAULT - Cannot read one of the strings
* * %-E2BIG - One of the strings is too large
* * %-ERANGE - One of the strings is outside of kernel address space
*/
__bpf_kfunc int bpf_strncasestr(const char *s1__ign, const char *s2__ign,
size_t len)
{
return __bpf_strnstr(s1__ign, s2__ign, len, true);
}

#ifdef CONFIG_KEYS
/**
* bpf_lookup_user_key - lookup a key by its serial
Expand Down Expand Up @@ -4367,7 +4419,9 @@ BTF_ID_FLAGS(func, bpf_strnlen);
BTF_ID_FLAGS(func, bpf_strspn);
BTF_ID_FLAGS(func, bpf_strcspn);
BTF_ID_FLAGS(func, bpf_strstr);
BTF_ID_FLAGS(func, bpf_strcasestr);
BTF_ID_FLAGS(func, bpf_strnstr);
BTF_ID_FLAGS(func, bpf_strncasestr);
#if defined(CONFIG_BPF_LSM) && defined(CONFIG_CGROUPS)
BTF_ID_FLAGS(func, bpf_cgroup_read_xattr, KF_RCU)
#endif
Expand Down
2 changes: 2 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/string_kfuncs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,9 @@ static const char * const test_cases[] = {
"strcspn_str",
"strcspn_reject",
"strstr",
"strcasestr",
"strnstr",
"strncasestr",
};

void run_too_long_tests(void)
Expand Down
12 changes: 12 additions & 0 deletions tools/testing/selftests/bpf/progs/string_kfuncs_failure1.c
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Expand Up @@ -45,8 +45,12 @@ SEC("syscall") __retval(USER_PTR_ERR)int test_strcspn_null1(void *ctx) { return
SEC("syscall") __retval(USER_PTR_ERR)int test_strcspn_null2(void *ctx) { return bpf_strcspn("hello", NULL); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strstr_null1(void *ctx) { return bpf_strstr(NULL, "hello"); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strstr_null2(void *ctx) { return bpf_strstr("hello", NULL); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strcasestr_null1(void *ctx) { return bpf_strcasestr(NULL, "hello"); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strcasestr_null2(void *ctx) { return bpf_strcasestr("hello", NULL); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strnstr_null1(void *ctx) { return bpf_strnstr(NULL, "hello", 1); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strnstr_null2(void *ctx) { return bpf_strnstr("hello", NULL, 1); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strncasestr_null1(void *ctx) { return bpf_strncasestr(NULL, "hello", 1); }
SEC("syscall") __retval(USER_PTR_ERR)int test_strncasestr_null2(void *ctx) { return bpf_strncasestr("hello", NULL, 1); }

/* Passing userspace ptr to string kfuncs */
SEC("syscall") __retval(USER_PTR_ERR) int test_strcmp_user_ptr1(void *ctx) { return bpf_strcmp(user_ptr, "hello"); }
Expand All @@ -65,8 +69,12 @@ SEC("syscall") __retval(USER_PTR_ERR) int test_strcspn_user_ptr1(void *ctx) { re
SEC("syscall") __retval(USER_PTR_ERR) int test_strcspn_user_ptr2(void *ctx) { return bpf_strcspn("hello", user_ptr); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strstr_user_ptr1(void *ctx) { return bpf_strstr(user_ptr, "hello"); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strstr_user_ptr2(void *ctx) { return bpf_strstr("hello", user_ptr); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strcasestr_user_ptr1(void *ctx) { return bpf_strcasestr(user_ptr, "hello"); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strcasestr_user_ptr2(void *ctx) { return bpf_strcasestr("hello", user_ptr); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strnstr_user_ptr1(void *ctx) { return bpf_strnstr(user_ptr, "hello", 1); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strnstr_user_ptr2(void *ctx) { return bpf_strnstr("hello", user_ptr, 1); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strncasestr_user_ptr1(void *ctx) { return bpf_strncasestr(user_ptr, "hello", 1); }
SEC("syscall") __retval(USER_PTR_ERR) int test_strncasestr_user_ptr2(void *ctx) { return bpf_strncasestr("hello", user_ptr, 1); }

#endif /* __TARGET_ARCH_s390 */

Expand All @@ -87,7 +95,11 @@ SEC("syscall") __retval(-EFAULT) int test_strcspn_pagefault1(void *ctx) { return
SEC("syscall") __retval(-EFAULT) int test_strcspn_pagefault2(void *ctx) { return bpf_strcspn("hello", invalid_kern_ptr); }
SEC("syscall") __retval(-EFAULT) int test_strstr_pagefault1(void *ctx) { return bpf_strstr(invalid_kern_ptr, "hello"); }
SEC("syscall") __retval(-EFAULT) int test_strstr_pagefault2(void *ctx) { return bpf_strstr("hello", invalid_kern_ptr); }
SEC("syscall") __retval(-EFAULT) int test_strcasestr_pagefault1(void *ctx) { return bpf_strcasestr(invalid_kern_ptr, "hello"); }
SEC("syscall") __retval(-EFAULT) int test_strcasestr_pagefault2(void *ctx) { return bpf_strcasestr("hello", invalid_kern_ptr); }
SEC("syscall") __retval(-EFAULT) int test_strnstr_pagefault1(void *ctx) { return bpf_strnstr(invalid_kern_ptr, "hello", 1); }
SEC("syscall") __retval(-EFAULT) int test_strnstr_pagefault2(void *ctx) { return bpf_strnstr("hello", invalid_kern_ptr, 1); }
SEC("syscall") __retval(-EFAULT) int test_strncasestr_pagefault1(void *ctx) { return bpf_strncasestr(invalid_kern_ptr, "hello", 1); }
SEC("syscall") __retval(-EFAULT) int test_strncasestr_pagefault2(void *ctx) { return bpf_strncasestr("hello", invalid_kern_ptr, 1); }

char _license[] SEC("license") = "GPL";
2 changes: 2 additions & 0 deletions tools/testing/selftests/bpf/progs/string_kfuncs_failure2.c
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Expand Up @@ -19,6 +19,8 @@ SEC("syscall") int test_strspn_accept_too_long(void *ctx) { return bpf_strspn("b
SEC("syscall") int test_strcspn_str_too_long(void *ctx) { return bpf_strcspn(long_str, "b"); }
SEC("syscall") int test_strcspn_reject_too_long(void *ctx) { return bpf_strcspn("b", long_str); }
SEC("syscall") int test_strstr_too_long(void *ctx) { return bpf_strstr(long_str, "hello"); }
SEC("syscall") int test_strcasestr_too_long(void *ctx) { return bpf_strcasestr(long_str, "hello"); }
SEC("syscall") int test_strnstr_too_long(void *ctx) { return bpf_strnstr(long_str, "hello", sizeof(long_str)); }
SEC("syscall") int test_strncasestr_too_long(void *ctx) { return bpf_strncasestr(long_str, "hello", sizeof(long_str)); }

char _license[] SEC("license") = "GPL";
13 changes: 13 additions & 0 deletions tools/testing/selftests/bpf/progs/string_kfuncs_success.c
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Expand Up @@ -33,14 +33,27 @@ __test(11) int test_strnlen(void *ctx) { return bpf_strnlen(str, 12); }
__test(5) int test_strspn(void *ctx) { return bpf_strspn(str, "ehlo"); }
__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(6) int test_strcasestr_found1(void *ctx) { return bpf_strcasestr(str, "world"); }
__test(6) int test_strcasestr_found2(void *ctx) { return bpf_strcasestr(str, "WORLD"); }
__test(-ENOENT) int test_strstr_notfound(void *ctx) { return bpf_strstr(str, "hi"); }
__test(-ENOENT) int test_strcasestr_notfound(void *ctx) { return bpf_strcasestr(str, "hi"); }
__test(0) int test_strstr_empty(void *ctx) { return bpf_strstr(str, ""); }
__test(0) int test_strcasestr_empty(void *ctx) { return bpf_strcasestr(str, ""); }
__test(0) int test_strnstr_found1(void *ctx) { return bpf_strnstr("", "", 0); }
__test(0) int test_strnstr_found2(void *ctx) { return bpf_strnstr(str, "hello", 5); }
__test(0) int test_strnstr_found3(void *ctx) { return bpf_strnstr(str, "hello", 6); }
__test(-ENOENT) int test_strnstr_notfound1(void *ctx) { return bpf_strnstr(str, "hi", 10); }
__test(-ENOENT) int test_strnstr_notfound2(void *ctx) { return bpf_strnstr(str, "hello", 4); }
__test(-ENOENT) int test_strnstr_notfound3(void *ctx) { return bpf_strnstr("", "a", 0); }
__test(0) int test_strnstr_empty(void *ctx) { return bpf_strnstr(str, "", 1); }
__test(0) int test_strncasestr_found1(void *ctx) { return bpf_strncasestr("", "", 0); }
__test(0) int test_strncasestr_found2(void *ctx) { return bpf_strncasestr(str, "hello", 5); }
__test(0) int test_strncasestr_found3(void *ctx) { return bpf_strncasestr(str, "hello", 6); }
__test(0) int test_strncasestr_found4(void *ctx) { return bpf_strncasestr(str, "HELLO", 5); }
__test(0) int test_strncasestr_found5(void *ctx) { return bpf_strncasestr(str, "HELLO", 6); }
__test(-ENOENT) int test_strncasestr_notfound1(void *ctx) { return bpf_strncasestr(str, "hi", 10); }
__test(-ENOENT) int test_strncasestr_notfound2(void *ctx) { return bpf_strncasestr(str, "hello", 4); }
__test(-ENOENT) int test_strncasestr_notfound3(void *ctx) { return bpf_strncasestr("", "a", 0); }
__test(0) int test_strncasestr_empty(void *ctx) { return bpf_strncasestr(str, "", 1); }

char _license[] SEC("license") = "GPL";
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