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new ec2a4105e2 swscale: avoid overflow in fast bilinear edge handling
ec2a4105e2 is described below
commit ec2a4105e2a5db5941e93326ee89897774a95462
Author: iSold Leo <[email protected]>
AuthorDate: Tue Aug 4 14:31:44 2026 +0800
Commit: michaelni <[email protected]>
CommitDate: Wed Aug 5 19:34:30 2026 +0000
swscale: avoid overflow in fast bilinear edge handling
The final edge clamp computes the source position using int
multiplication before shifting. With sufficiently wide inputs this
overflows, which may suppress the clamp and leave the last output
pixels interpolated with the padding byte.
Promote the multiplication to int64_t in the C, MMXEXT and VSX
implementations.
Add a regression test covering the rightmost pixel of a wide upscale,
which is wrong before this change on both the C and the MMXEXT path.
Fixes: signed integer overflow: 15 * 255918080 cannot be represented in
type 'int'
Fixes: #21591
Signed-off-by: iSold Leo <[email protected]>
---
libswscale/hscale_fast_bilinear.c | 4 ++--
libswscale/ppc/swscale_vsx.c | 4 ++--
libswscale/x86/hscale_fast_bilinear_simd.c | 4 ++--
tests/fate/filter-video.mak | 3 +++
tests/ref/fate/filter-scale-fast-bilinear-wide-edge | 6 ++++++
5 files changed, 15 insertions(+), 6 deletions(-)
diff --git a/libswscale/hscale_fast_bilinear.c
b/libswscale/hscale_fast_bilinear.c
index abcfb95e2c..331a3c95e0 100644
--- a/libswscale/hscale_fast_bilinear.c
+++ b/libswscale/hscale_fast_bilinear.c
@@ -31,7 +31,7 @@ void ff_hyscale_fast_c(SwsInternal *c, int16_t *dst, int
dstWidth,
dst[i] = (src[xx] << 7) + (src[xx + 1] - src[xx]) * xalpha;
xpos += xInc;
}
- for (i=dstWidth-1; (i*xInc)>>16 >=srcW-1; i--)
+ for (i=dstWidth-1; (i*(int64_t)xInc)>>16 >=srcW-1; i--)
dst[i] = src[srcW-1]*128;
}
@@ -48,7 +48,7 @@ void ff_hcscale_fast_c(SwsInternal *c, int16_t *dst1, int16_t
*dst2,
dst2[i] = (src2[xx] * (xalpha ^ 127) + src2[xx + 1] * xalpha);
xpos += xInc;
}
- for (i=dstWidth-1; (i*xInc)>>16 >=srcW-1; i--) {
+ for (i=dstWidth-1; (i*(int64_t)xInc)>>16 >=srcW-1; i--) {
dst1[i] = src1[srcW-1]*128;
dst2[i] = src2[srcW-1]*128;
}
diff --git a/libswscale/ppc/swscale_vsx.c b/libswscale/ppc/swscale_vsx.c
index 21fb43092d..8bbe6cde65 100644
--- a/libswscale/ppc/swscale_vsx.c
+++ b/libswscale/ppc/swscale_vsx.c
@@ -1754,7 +1754,7 @@ static void hyscale_fast_vsx(SwsInternal *c, int16_t
*dst, int dstWidth,
xpos += xInc * 16;
}
- for (i=dstWidth-1; (i*xInc)>>16 >=srcW-1; i--)
+ for (i=dstWidth-1; (i*(int64_t)xInc)>>16 >=srcW-1; i--)
dst[i] = src[srcW-1]*128;
}
@@ -1850,7 +1850,7 @@ static void hcscale_fast_vsx(SwsInternal *c, int16_t
*dst1, int16_t *dst2,
xpos += xInc * 16;
}
- for (i=dstWidth-1; (i*xInc)>>16 >=srcW-1; i--) {
+ for (i=dstWidth-1; (i*(int64_t)xInc)>>16 >=srcW-1; i--) {
dst1[i] = src1[srcW-1]*128;
dst2[i] = src2[srcW-1]*128;
}
diff --git a/libswscale/x86/hscale_fast_bilinear_simd.c
b/libswscale/x86/hscale_fast_bilinear_simd.c
index d8a4e444b4..3f3c799a33 100644
--- a/libswscale/x86/hscale_fast_bilinear_simd.c
+++ b/libswscale/x86/hscale_fast_bilinear_simd.c
@@ -275,7 +275,7 @@ void ff_hyscale_fast_mmxext(SwsInternal *c, int16_t *dst,
#endif
);
- for (i=dstWidth-1; (i*xInc)>>16 >=srcW-1; i--)
+ for (i=dstWidth-1; (i*(int64_t)xInc)>>16 >=srcW-1; i--)
dst[i] = src[srcW-1]*128;
}
@@ -352,7 +352,7 @@ void ff_hcscale_fast_mmxext(SwsInternal *c, int16_t *dst1,
int16_t *dst2,
#endif
);
- for (i=dstWidth-1; (i*xInc)>>16 >=srcW-1; i--) {
+ for (i=dstWidth-1; (i*(int64_t)xInc)>>16 >=srcW-1; i--) {
dst1[i] = src1[srcW-1]*128;
dst2[i] = src2[srcW-1]*128;
}
diff --git a/tests/fate/filter-video.mak b/tests/fate/filter-video.mak
index 0eb2e7076c..f8c0ffc3cb 100644
--- a/tests/fate/filter-video.mak
+++ b/tests/fate/filter-video.mak
@@ -181,6 +181,9 @@ FATE_FILTER-$(call FILTERFRAMECRC, TESTSRC FORMAT CONCAT
SCALE, LAVFI_INDEV FILE
fate-filter-lavd-scalenorm: tests/data/filtergraphs/scalenorm
fate-filter-lavd-scalenorm: CMD = framecrc -f lavfi -graph_file
$(TARGET_PATH)/tests/data/filtergraphs/scalenorm -i dummy
+FATE_FILTER-$(call FILTERFRAMECRC, COLOR FORMAT SCALE CROP) +=
fate-filter-scale-fast-bilinear-wide-edge
+fate-filter-scale-fast-bilinear-wide-edge: CMD = framecrc -flags bitexact
-lavfi
color=c=red:s=40000x1:r=1:d=1,format=yuv444p,scale=40032:1:flags=fast_bilinear,crop=1:1:40031:0
-frames:v 1
+
FATE_FILTER-$(call FILTERFRAMECRC, TESTSRC2 FEEDBACK HFLIP, LAVFI_INDEV) +=
fate-filter-feedback-hflip
fate-filter-feedback-hflip: CMD = framecrc -f lavfi -i testsrc2=d=1 -vf
"[in][hflipin]feedback=x=0:y=0:w=100:h=100[out][hflipout];[hflipout]hflip[hflipin]"
diff --git a/tests/ref/fate/filter-scale-fast-bilinear-wide-edge
b/tests/ref/fate/filter-scale-fast-bilinear-wide-edge
new file mode 100644
index 0000000000..8b38823e97
--- /dev/null
+++ b/tests/ref/fate/filter-scale-fast-bilinear-wide-edge
@@ -0,0 +1,6 @@
+#tb 0: 1/1
+#media_type 0: video
+#codec_id 0: rawvideo
+#dimensions 0: 1x1
+#sar 0: 0/1
+0, 0, 0, 1, 3, 0x0297019b
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