bpf: Check params size before reading reserved fields

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bpf_crypto_ctx_create() is a kfunc whose second argument is declared
with the __sz annotation, so the verifier only guarantees that
params__sz bytes of params are valid.  The function nevertheless reads
params->reserved[0] and params->reserved[1] (offsets 14 and 15) before
comparing params__sz against the size of struct bpf_crypto_params, so a
BPF program can pass a shorter buffer and have the kernel read past the
region that was validated for it.

Move the size check in front of the reserved field reads.

Fixes: 3e1c6f3540 ("bpf: make common crypto API for TC/XDP programs")
Reported-by: Vega <vega@nebusec.ai>
Signed-off-by: Yuqi Xu <xuyuqiabc@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Ren Wei <weir@nebusec.ai>
Link: https://patch.msgid.link/4f3ab4b03e79017e215521743996555439bf0bb3.1789802413.git.xuyuqiabc@gmail.com

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Yuqi Xu 2026-09-19 16:45:02 +08:00 • committed by Alexei Starovoitov

parent e3b6cb020e

commit a11212910c

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kernel/bpf/crypto.c

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