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tagdemux: Fix crash when presented with malformed files

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There's a race condition in gsttagdemux.c between typefinding and the
end-of-stream event. If TYPE_FIND_MAX_SIZE is exceeded,
demux->priv->collect is set to NULL and an error is returned. However,
the end-of-stream event causes one last attempt at typefinding to occur.

This leads to gst_tag_demux_trim_buffer() being called with the NULL
demux->priv->collect buffer which it attempts to dereference, resulting
in a segfault.

The malicious MP3 can be created by:

printf "\x49\x44\x33\x04\x00\x00\x00\x00\x00\x00%s", \
    "$(dd if=/dev/urandom bs=1K count=200)" > malicious.mp3

This creates a valid ID3 header which gets us as far as typefinding. The
crash can then be reproduced with the following pipeline:

gst-launch-1.0 -e filesrc location=malicious.mp3 ! queue ! decodebin ! audioconvert ! vorbisenc ! oggmux ! filesink location=malicious.ogg

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/967

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/1620>
This commit is contained in:
Jeremy Cline 2021-11-21 17:52:48 -05:00 committed by GStreamer Marge Bot
parent 34b54ca665
commit 3ddb4c6f0e
1 changed files with 5 additions and 3 deletions
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8
subprojects/gst-plugins-base/gst-libs/gst/tag/gsttagdemux.c
View file

@ -655,9 +655,11 @@ gst_tag_demux_chain_buffer (GstTagDemux * demux, GstBuffer * buf,
/* Trim the buffer and adjust offset for typefinding */
typefind_buf = demux->priv->collect;
gst_buffer_ref (typefind_buf);
if (!gst_tag_demux_trim_buffer (demux, &typefind_buf, &typefind_size))
return GST_FLOW_EOS;
if (typefind_buf) {
gst_buffer_ref (typefind_buf);
if (!gst_tag_demux_trim_buffer (demux, &typefind_buf, &typefind_size))
return GST_FLOW_EOS;
}
if (typefind_buf == NULL)
break; /* Still need more data */