Sorry! Let's try an attachment then. On 16 November 2017 at 14:36, Michael Niedermayer <mich...@niedermayer.cc> wrote: > On Thu, Nov 16, 2017 at 12:41:32PM -0800, Nick Lewycky wrote: >> I initially discovered a signed integer overflow on this line. Since >> this value is updated in multiple threads, I use an atomic update and >> as it happens atomic addition is defined to wrap around. However, >> there's still a potential bug in that the error_count may wrap around >> and equal zero again causing problems down the line. >> >> --- >> libavcodec/mpeg12dec.c | 3 ++- >> 1 file changed, 2 insertions(+), 1 deletion(-) >> >> diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c >> index d5bc5f21b2..b7c3b5106e 100644 >> --- a/libavcodec/mpeg12dec.c >> +++ b/libavcodec/mpeg12dec.c >> @@ -28,6 +28,7 @@ >> #define UNCHECKED_BITSTREAM_READER 1 >> #include <inttypes.h> >> >> +#include "libavutil/atomic.h" >> #include "libavutil/attributes.h" >> #include "libavutil/imgutils.h" >> #include "libavutil/internal.h" >> @@ -2476,7 +2477,7 @@ static int decode_chunks(AVCodecContext *avctx, >> AVFrame *picture, >> &s2->thread_context[0], NULL, >> s->slice_count, sizeof(void *)); >> for (i = 0; i < s->slice_count; i++) >> - s2->er.error_count += >> s2->thread_context[i]->er.error_count; >> + >> avpriv_atomic_int_add_and_fetch(&s2->er.error_count, >> s2->thread_context[i]->er.error_count); >> } > > This patch is corrupted by newlines > > [...] > > -- > Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB > > Dictatorship naturally arises out of democracy, and the most aggravated > form of tyranny and slavery out of the most extreme liberty. -- Plato > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel >
From cd8ed0ee35853ae089df3d904846879ce4f00c4a Mon Sep 17 00:00:00 2001 From: Nick Lewycky <nlewy...@google.com> Date: Thu, 16 Nov 2017 11:50:38 -0800 Subject: [PATCH] libavcodec/mpeg12dec: Use atomic addition for value updated in multiple threads.
---
libavcodec/mpeg12dec.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/libavcodec/mpeg12dec.c b/libavcodec/mpeg12dec.c
index d5bc5f21b2..b7c3b5106e 100644
--- a/libavcodec/mpeg12dec.c
+++ b/libavcodec/mpeg12dec.c
@@ -28,6 +28,7 @@
#define UNCHECKED_BITSTREAM_READER 1
#include <inttypes.h>
+#include "libavutil/atomic.h"
#include "libavutil/attributes.h"
#include "libavutil/imgutils.h"
#include "libavutil/internal.h"
@@ -2476,7 +2477,7 @@ static int decode_chunks(AVCodecContext *avctx, AVFrame *picture,
&s2->thread_context[0], NULL,
s->slice_count, sizeof(void *));
for (i = 0; i < s->slice_count; i++)
- s2->er.error_count += s2->thread_context[i]->er.error_count;
+ avpriv_atomic_int_add_and_fetch(&s2->er.error_count, s2->thread_context[i]->er.error_count);
}
ret = slice_end(avctx, picture);
--
2.15.0.448.gf294e3d99a-goog
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