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([2606:6d00:15:e221::5ac]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-90ce4514f3esm21370506d6.41.2026.08.28.11.43.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Aug 2026 11:43:19 -0700 (PDT) Message-ID: Subject: Re: [PATCH] media: v4l2-h264: Fix memcmp() size in B1 reference list comparison From: Nicolas Dufresne To: Haotian Zhang , mchehab@kernel.org Cc: boris.brezillon@collabora.com, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Date: Fri, 28 Aug 2026 14:43:18 -0400 In-Reply-To: <20260828021739.25766-1-vulab@iscas.ac.cn> References: <20260828021739.25766-1-vulab@iscas.ac.cn> Autocrypt: addr=nicolas@ndufresne.ca; prefer-encrypt=mutual; keydata=mDMEaCN2ixYJKwYBBAHaRw8BAQdAM0EHepTful3JOIzcPv6ekHOenE1u0vDG1gdHFrChD /e0J05pY29sYXMgRHVmcmVzbmUgPG5pY29sYXNAbmR1ZnJlc25lLmNhPoicBBMWCgBEAhsDBQsJCA cCAiICBhUKCQgLAgQWAgMBAh4HAheABQkJZfd1FiEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrjo CGQEACgkQ2UGUUSlgcvQlQwD/RjpU1SZYcKG6pnfnQ8ivgtTkGDRUJ8gP3fK7+XUjRNIA/iXfhXMN abIWxO2oCXKf3TdD7aQ4070KO6zSxIcxgNQFtDFOaWNvbGFzIER1ZnJlc25lIDxuaWNvbGFzLmR1Z nJlc25lQGNvbGxhYm9yYS5jb20+iJkEExYKAEECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4 AWIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaCyyxgUJCWX3dQAKCRDZQZRRKWBy9ARJAP96pFmLffZ smBUpkyVBfFAf+zq6BJt769R0al3kHvUKdgD9G7KAHuioxD2v6SX7idpIazjzx8b8rfzwTWyOQWHC AAS0LU5pY29sYXMgRHVmcmVzbmUgPG5pY29sYXMuZHVmcmVzbmVAZ21haWwuY29tPoiZBBMWCgBBF iEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrGYCGwMFCQll93UFCwkIBwICIgIGFQoJCAsCBBYCAw ECHgcCF4AACgkQ2UGUUSlgcvRObgD/YnQjfi4+L8f4fI7p1pPMTwRTcaRdy6aqkKEmKsCArzQBAK8 bRLv9QjuqsE6oQZra/RB4widZPvphs78H0P6NmpIJ Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-EhY9WrS0/N/5NtB6wlfl" User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 --=-EhY9WrS0/N/5NtB6wlfl Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Le vendredi 28 ao=C3=BBt 2026 =C3=A0 10:17 +0800, Haotian Zhang a =C3=A9cri= t=C2=A0: > In v4l2_h264_build_b_ref_lists(), the B0/B1 list equality > check passes the entry count builder->num_valid to memcmp() > instead of a byte size. Since struct v4l2_h264_reference is > two bytes (fields and index), only half of each list is > compared, so distinct lists can be wrongly treated as equal > and trigger an incorrect swap(b1_reflist[0], b1_reflist[1]). >=20 > Change the memcmp() size argument to builder->num_valid * > sizeof(*b1_reflist) so that the full byte length of both > reference lists is compared. >=20 > Fixes: 624922a2739b ("media: v4l2-core: Add helpers to build the H264 P/B= 0/B1 reflists") > Signed-off-by: Haotian Zhang > --- > drivers/media/v4l2-core/v4l2-h264.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) >=20 > diff --git a/drivers/media/v4l2-core/v4l2-h264.c b/drivers/media/v4l2-cor= e/v4l2-h264.c > index c00197d095e7..1b1421caf488 100644 > --- a/drivers/media/v4l2-core/v4l2-h264.c > +++ b/drivers/media/v4l2-core/v4l2-h264.c > @@ -440,7 +440,8 @@ v4l2_h264_build_b_ref_lists(const struct v4l2_h264_re= flist_builder *builder, > } > =20 > if (builder->num_valid > 1 && > - !memcmp(b1_reflist, b0_reflist, builder->num_valid)) > + !memcmp(b1_reflist, b0_reflist, > + builder->num_valid * sizeof(*b1_reflist))) One last comment, I think this would be more consistent with the memcpy() c= alls: + sizeof(b1_reflist[0]) * builder->num_valid)) Nicolas > swap(b1_reflist[0], b1_reflist[1]); > =20 > print_ref_list_b(builder, b0_reflist, 0); --=-EhY9WrS0/N/5NtB6wlfl Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCapHWxgAKCRDZQZRRKWBy 9D5hAQD5uGsohrgmxddLCQ9VT8Nsso+m71cU2QJcybfjw84KogD/an36TroA8CFI b+0W8ellAI+OhfBX4jig/Xw6EuAyMAk= =JMRA -----END PGP SIGNATURE----- --=-EhY9WrS0/N/5NtB6wlfl--