On 5/6/2023 12:08 PM, Michael Niedermayer wrote:
On Fri, May 05, 2023 at 07:36:05PM -0300, James Almer wrote:
On 4/16/2023 1:48 PM, Michael Niedermayer wrote:
Fixes: signed integer overflow: 3011809745540902265 + 6323452730883571725
cannot be represented in type 'long'
Fixes:
45982/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_FLAC_fuzzer-6687553022722048
Found-by: continuous fuzzing process
https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <[email protected]>
---
libavcodec/flacdec.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libavcodec/flacdec.c b/libavcodec/flacdec.c
index cc778a8dff1..524a0469495 100644
--- a/libavcodec/flacdec.c
+++ b/libavcodec/flacdec.c
@@ -513,7 +513,7 @@ static int decode_subframe_lpc_33bps(FLACContext *s,
int64_t *decoded,
for (i = pred_order; i < s->blocksize; i++, decoded++) {
int64_t sum = 0;
for (j = 0; j < pred_order; j++)
- sum += (int64_t)coeffs[j] * decoded[j];
+ sum += (int64_t)coeffs[j] * (uint64_t)decoded[j];
Why not instead do
sum = av_sat_add64(sum, (int64_t)coeffs[j] * decoded[j]);
Why should this be clipping ?
flac is a lossless codec, i see nothing in the specification that calls for
cliping.
No, but an overflowing case like 3011809745540902265 +
6323452730883571725 isn't supported either and will generate bad output,
so might as well use an optimized function for this.
Also, decoded[j] is an int64_t, so wouldn't coeffs[j] be promoted if you
swap the order in the multiplication, thus saving the cast?
it can be shuffled around to achieve the same, do you prefer
coeffs[j] * (uint64_t)decoded[j]; ?
No gain doing that compared to your first version. I suggested it for
av_sat_add64(), which i insist you should use, if you want with a
comment about it being there not for spec reasons but to prevent integer
overflows, and removing all casts.
thx
[...]
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