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[FFmpeg-devel,PATCHv4] swscale: prevent undefined behaviour in the PUTRGBA macro

Message ID 20240709214132.12016-1-gseanmcg@gmail.com
State New
Headers show
Series [FFmpeg-devel,PATCHv4] swscale: prevent undefined behaviour in the PUTRGBA macro | expand

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Commit Message

Sean McGovern July 9, 2024, 9:41 p.m. UTC 
For even small values of 'asrc[x]', shifting them by 24 bits or more
will cause arithmetic overflow and be caught by
GCC's undefined behaviour sanitizer.

Ensure the values do not overflow by up-casting the bracketed
expressions involving 'asrc' to uint32_t.
---
 libswscale/yuv2rgb.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Michael Niedermayer July 10, 2024, 4:09 p.m. UTC | #1 
On Tue, Jul 09, 2024 at 05:41:32PM -0400, Sean McGovern wrote:
> For even small values of 'asrc[x]', shifting them by 24 bits or more
> will cause arithmetic overflow and be caught by
> GCC's undefined behaviour sanitizer.
> 
> Ensure the values do not overflow by up-casting the bracketed
> expressions involving 'asrc' to uint32_t.
> ---
>  libswscale/yuv2rgb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

will apply

thx

[...]
diff mbox series

Patch

diff --git a/libswscale/yuv2rgb.c b/libswscale/yuv2rgb.c
index 977eb3a7dd..cfbc54abd0 100644
--- a/libswscale/yuv2rgb.c
+++ b/libswscale/yuv2rgb.c
@@ -100,9 +100,9 @@  const int *sws_getCoefficients(int colorspace)
 
 #define PUTRGBA(dst, ysrc, asrc, i, abase)                              \
     Y              = ysrc[2 * i];                                       \
-    dst[2 * i]     = r[Y] + g[Y] + b[Y] + (asrc[2 * i]     << abase);   \
+    dst[2 * i]     = r[Y] + g[Y] + b[Y] + ((uint32_t)(asrc[2 * i])     << abase);   \
     Y              = ysrc[2 * i + 1];                                   \
-    dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + (asrc[2 * i + 1] << abase);
+    dst[2 * i + 1] = r[Y] + g[Y] + b[Y] + ((uint32_t)(asrc[2 * i + 1]) << abase);
 
 #define PUTRGB48(dst, src, asrc, i, abase)          \
     Y                = src[ 2 * i];                 \