[FFmpeg-cvslog] swscale/output: alpha can become negative after scaling, use multiply

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Jun 16 01:51:22 2024 +0200| [9e6c5b6e865a6b1b9c3a471fc06143f11e69d71b] | committer: Michael Niedermayer

swscale/output: alpha can become negative after scaling, use multiply

Fixes: left shift of negative value -3245
Fixes: 69047/clusterfuzz-testcase-minimized-ffmpeg_SWS_fuzzer-6571511551950848

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=9e6c5b6e865a6b1b9c3a471fc06143f11e69d71b
---

 libswscale/output.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/libswscale/output.c b/libswscale/output.c
index b234f9c6b9..f9ce43dde8 100644
--- a/libswscale/output.c
+++ b/libswscale/output.c
@@ -1221,8 +1221,8 @@ yuv2rgba64_1_c_template(SwsContext *c, const int32_t *buf0,
             Y2 += (1 << 13) - (1 << 29);
 
             if (hasAlpha) {
-                A1 = abuf0[i * 2    ] << 11;
-                A2 = abuf0[i * 2 + 1] << 11;
+                A1 = abuf0[i * 2    ] * (1 << 11);
+                A2 = abuf0[i * 2 + 1] * (1 << 11);
 
                 A1 += 1 << 13;
                 A2 += 1 << 13;
@@ -1267,8 +1267,8 @@ yuv2rgba64_1_c_template(SwsContext *c, const int32_t *buf0,
             Y2 += (1 << 13) - (1 << 29);
 
             if (hasAlpha) {
-                A1 = abuf0[i * 2    ] << 11;
-                A2 = abuf0[i * 2 + 1] << 11;
+                A1 = abuf0[i * 2    ] * (1 << 11);
+                A2 = abuf0[i * 2 + 1] * (1 << 11);
 
                 A1 += 1 << 13;
                 A2 += 1 << 13;
@@ -1439,7 +1439,7 @@ yuv2rgba64_full_1_c_template(SwsContext *c, const int32_t *buf0,
             Y += (1 << 13) - (1 << 29);
 
             if (hasAlpha) {
-                A = abuf0[i] << 11;
+                A = abuf0[i] * (1 << 11);
 
                 A += 1 << 13;
             }
@@ -1472,7 +1472,7 @@ yuv2rgba64_full_1_c_template(SwsContext *c, const int32_t *buf0,
             Y += (1 << 13) - (1 << 29);
 
             if (hasAlpha) {
-                A = abuf0[i] << 11;
+                A = abuf0[i] * (1 << 11);
 
                 A += 1 << 13;
             }