[FFmpeg-cvslog] avformat/dxa: Adjust order of operations around block align

[Michael Niedermayer]

ffmpeg | branch: release/3.4 | Michael Niedermayer <michael at niedermayer.cc> | Sat Sep 30 00:51:29 2023 +0200| [fd02b195bf9f5f1cd28cd41108d8c3c3cd20b3cc] | committer: Michael Niedermayer

avformat/dxa: Adjust order of operations around block align

Fixes: 51896/clusterfuzz-testcase-minimized-ffmpeg_dem_DXA_fuzzer-5730576523198464
Fixes: signed integer overflow: 2147483566 + 82 cannot be represented in type 'int'

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit 50d8e4f27398fd5778485a827d7a2817921f8540)
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=fd02b195bf9f5f1cd28cd41108d8c3c3cd20b3cc
---

 libavformat/dxa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/libavformat/dxa.c b/libavformat/dxa.c
index 0d820c7413..c94665676a 100644
--- a/libavformat/dxa.c
+++ b/libavformat/dxa.c
@@ -122,7 +122,7 @@ static int dxa_read_header(AVFormatContext *s)
         if(ast->codecpar->block_align) {
             if (c->bpc > INT_MAX - ast->codecpar->block_align + 1)
                 return AVERROR_INVALIDDATA;
-            c->bpc = ((c->bpc + ast->codecpar->block_align - 1) / ast->codecpar->block_align) * ast->codecpar->block_align;
+            c->bpc = ((c->bpc - 1 + ast->codecpar->block_align) / ast->codecpar->block_align) * ast->codecpar->block_align;
         }
         c->bytes_left = fsize;
         c->wavpos = avio_tell(pb);