bpf: Fix bpf_strnstr() to handle suffix match cases better

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bpf_strnstr() should not treat the ending '\0' of s2 as a matching character
if the parameter 'len' equal to s2 string length, for example:

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

This patch makes (1) return 0, fix just the `len == strlen(s2)` case.

And fix a more general case when s2 is a suffix of the first len
characters of s1.

Fixes: e91370550f ("bpf: Add kfuncs for read-only string operations")
Signed-off-by: Rong Tao <rongtao@cestc.cn>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/tencent_17DC57B9D16BC443837021BEACE84B7C1507@qq.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Rong Tao 2025-08-30 00:31:58 +08:00 • committed by Alexei Starovoitov

parent 387be23a95

commit 7edfc02470

1 changed files with 8 additions and 1 deletions

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kernel/bpf/helpers.c

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