[FFmpeg-devel] [PATCH]lavfi/rotate: Fix undefined behaviour

[Carl Eugen Hoyos <ceffmpeg@gmail.com>]

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Hi!

Attached patch fixes ticket #9799.

Please comment, Carl Eugen

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From 2cce687961c3b56a92d88184269bf9fa075ae297 Mon Sep 17 00:00:00 2001
From: Carl Eugen Hoyos <ceffmpeg@gmail.com>
Date: Thu, 1 Sep 2022 20:55:54 +0200
Subject: [PATCH] lavfi/rotate: Avoid undefined behaviour.

Fixes the following integer overflows:
libavfilter/vf_rotate.c:273:13: runtime error: signed integer overflow: 92951468 + 2058533568 cannot be represented in type 'int'
libavfilter/vf_rotate.c:273:37: runtime error: signed integer overflow: 39684 * 54149 cannot be represented in type 'int'
libavfilter/vf_rotate.c:272:13: runtime error: signed integer overflow: 247587320 + 1900985032 cannot be represented in type 'int'
libavfilter/vf_rotate.c:272:37: runtime error: signed integer overflow: 42584 * 50430 cannot be represented in type 'int'
libavfilter/vf_rotate.c:272:50: runtime error: signed integer overflow: 65083 * 52912 cannot be represented in type 'int'
libavfilter/vf_rotate.c:273:50: runtime error: signed integer overflow: 65286 * 38044 cannot be represented in type 'int'

Fixes ticket #9799, different output with different compilers.
---
 libavfilter/vf_rotate.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libavfilter/vf_rotate.c b/libavfilter/vf_rotate.c
index 4429e3d543..d319dfe3d9 100644
--- a/libavfilter/vf_rotate.c
+++ b/libavfilter/vf_rotate.c
@@ -269,8 +269,8 @@ static uint8_t *interpolate_bilinear16(uint8_t *dst_color,
         int s01 = AV_RL16(&src[src_linestep * int_x1 + i + src_linesize * int_y ]);
         int s10 = AV_RL16(&src[src_linestep * int_x  + i + src_linesize * int_y1]);
         int s11 = AV_RL16(&src[src_linestep * int_x1 + i + src_linesize * int_y1]);
-        int s0 = (((1<<16) - frac_x)*s00 + frac_x*s01);
-        int s1 = (((1<<16) - frac_x)*s10 + frac_x*s11);
+        int64_t s0 = (((int64_t)(1<<16) - frac_x)*s00 + (int64_t)frac_x*s01);
+        int64_t s1 = (((int64_t)(1<<16) - frac_x)*s10 + (int64_t)frac_x*s11);
 
         AV_WL16(&dst_color[i], ((int64_t)((1<<16) - frac_y)*s0 + (int64_t)frac_y*s1) >> 32);
     }
-- 
2.30.1


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