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Thu, 11 Dec 2025 08:33:07 +0200 (EET) MIME-Version: 1.0 To: ffmpeg-devel@ffmpeg.org Date: Thu, 11 Dec 2025 06:33:07 -0000 Message-ID: <176543478793.39.11183944168913956800@2cb04c0e5124> Message-ID-Hash: JMT5KSKRMSX6SUMK22UMUGHEAUDJK527 X-Message-ID-Hash: JMT5KSKRMSX6SUMK22UMUGHEAUDJK527 X-MailFrom: code@ffmpeg.org X-Mailman-Rule-Hits: nonmember-moderation X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; header-match-ffmpeg-devel.ffmpeg.org-0; header-match-ffmpeg-devel.ffmpeg.org-1; header-match-ffmpeg-devel.ffmpeg.org-2; header-match-ffmpeg-devel.ffmpeg.org-3; emergency; member-moderation X-Mailman-Version: 3.3.10 Precedence: list Reply-To: FFmpeg development discussions and patches Subject: [FFmpeg-devel] [PATCH] VMD demuxer: precedence bug makes failed reads look like success (PR #21165) List-Id: FFmpeg development discussions and patches Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: ruikai via ffmpeg-devel Cc: ruikai Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Archived-At: List-Archive: List-Post: PR #21165 opened by ruikai URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21165 Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/21165.patch In `libavformat/sierravmd.c (vmd_read_header)`, the header read check was written as: ``` if ((ret = ffio_read_size(pb, vmd->vmd_header, VMD_HEADER_SIZE) < 0)) return ret; ``` Due to operator precedence, this stores the boolean result of the comparison into ret, so a failed read (negative return) becomes `ret = 1,` which is treated as success. `avformat_open_input() `then completes with zero streams and uninitialized state, letting the demuxer proceed into `vmd_read_packet()` with bogus tables. We have not reported this as a security issue because we did not demonstrate a ground-truth crash in validation, though it has an interesting possibility as an OOB primitive. Found-by: Pwno >>From d158e8605cdfcdbd973bddbed52fcc511e590a88 Mon Sep 17 00:00:00 2001 From: Ruikai Peng Date: Thu, 11 Dec 2025 06:27:48 +0000 Subject: [PATCH] VMD demuxer: precedence bug makes failed reads look like success --- libavformat/sierravmd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libavformat/sierravmd.c b/libavformat/sierravmd.c index bb1d1c5df7..2519756533 100644 --- a/libavformat/sierravmd.c +++ b/libavformat/sierravmd.c @@ -103,7 +103,7 @@ static int vmd_read_header(AVFormatContext *s) /* fetch the main header, including the 2 header length bytes */ avio_seek(pb, 0, SEEK_SET); - if ((ret = ffio_read_size(pb, vmd->vmd_header, VMD_HEADER_SIZE) < 0)) + if ((ret = ffio_read_size(pb, vmd->vmd_header, VMD_HEADER_SIZE)) < 0) return ret; width = AV_RL16(&vmd->vmd_header[12]); -- 2.49.1 _______________________________________________ ffmpeg-devel mailing list -- ffmpeg-devel@ffmpeg.org To unsubscribe send an email to ffmpeg-devel-leave@ffmpeg.org