On Mon, Nov 16, 2020 at 07:07:21AM +0100, Anton Khirnov wrote: > Quoting Michael Niedermayer (2020-11-16 01:05:07) > > On Sat, Nov 14, 2020 at 11:12:15AM +0100, Anton Khirnov wrote: > > > Quoting Michael Niedermayer (2020-11-10 00:04:54) > > > > Fixes: OOM > > > > Fixes: > > > > 26934/clusterfuzz-testcase-minimized-ffmpeg_dem_W64_fuzzer-5996784213819392 > > > > > > > > Found-by: continuous fuzzing process > > > > https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg > > > > Signed-off-by: Michael Niedermayer <mich...@niedermayer.cc> > > > > --- > > > > libavformat/wavdec.c | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > diff --git a/libavformat/wavdec.c b/libavformat/wavdec.c > > > > index a81f2c7a67..6e5f4ccc12 100644 > > > > --- a/libavformat/wavdec.c > > > > +++ b/libavformat/wavdec.c > > > > @@ -920,7 +920,7 @@ static int w64_read_header(AVFormatContext *s) > > > > if (chunk_size == UINT32_MAX || (filesize >= 0 && > > > > chunk_size > filesize)) > > > > return AVERROR_INVALIDDATA; > > > > > > > > - value = av_mallocz(chunk_size + 1); > > > > + value = av_malloc(chunk_size + 1); > > > > > > This looks highly suspicious as a fix for anything other than > > > performance. > > > > if iam not mistaken: > > The allocation doesnzt trigger OOM as no physical memory is allocated > > but once it is written to "z" it does and then OOMs > > if OTOH its written too while data is read from somewhere then a > > EOF ends writing and no OOM would happen > > That is highly dependent on your OS and its configuration (e.g. you can > disable overcommit on Linux).
yes thats correct If the OS supports this then a OOM can be avoided, otherwise it will OOM Avoiding the OOM in the remaining cases seems too messy to me. OTOH this here is a rather simple change ... > > Also, there seems to be a check right above that fails if chunk_size is > larger than the file size. The file size is not always known thx [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB He who knows, does not speak. He who speaks, does not know. -- Lao Tsu
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