From: Rong Tao rongtao@cestc.cn

strnstr should not treat the ending '\0' of s2 as a matching character, otherwise the parameter 'len' will be meaningless, for example:

1. bpf_strnstr("openat", "open", 4) = -ENOENT 2. bpf_strnstr("openat", "open", 5) = 0

This patch makes (1) return 0, indicating a successful match.

Signed-off-by: Rong Tao rongtao@cestc.cn --- kernel/bpf/helpers.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c index 401b4932cc49..ced7132980fe 100644 --- a/kernel/bpf/helpers.c +++ b/kernel/bpf/helpers.c @@ -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;