Max Kellermann authored Jul 06, 2016 and Erik de Castro Lopo committed Jul 10, 2016

FLAC__stream_decoder_process_single() ignores frame_sync_() errors,
which means the caller cannot rely solely on the boolean return value,
it is also required to check the new "state".

After FLAC__stream_decoder_process_until_end_of_metadata(),
state==SEARCH_FOR_FRAME_SYNC and
last_frame.header.number_type==FRAME_NUMBER.  When an application
seeks at this time, but an I/O error occurs, then
FLAC__stream_decoder_process_single() returns true, but no frame has
been read yet, i.e. last_frame.header.number_type is still
FRAME_NUMBER.  This triggers the assertion in
seek_to_absolute_sample_():

 FLAC__ASSERT(decoder->private_->last_frame.header.number_type == FLAC__FRAME_NUMBER_TYPE_SAMPLE_NUMBER);

So what needs to be done is check for state==ABORTED after the
FLAC__stream_decoder_process_single() call.

This bug can be triggered remotely with the Music Player Daemon
(https://www.musicpd.org/

), and crashes the process.

Signed-off-by: Erik de Castro Lopo <erikd@mega-nerd.com>
Closes: https://github.com/xiph/flac/pull/12