Calling ffio_ensure_seekback() if ffio_init_checksum() has been called
on the same context can lead to out of bounds memory accesses and
crashes. The reason is that ffio_ensure_seekback() does not update
checksum_ptr after reallocating the buffer, resulting in a dangling
pointer.
This effectively fixes potential crashes when opening mp3 files.
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
int max_buffer_size = s->max_packet_size ?
s->max_packet_size : IO_BUFFER_SIZE;
int filled = s->buf_end - s->buffer;
+ ptrdiff_t checksum_ptr_offset = s->checksum_ptr ? s->checksum_ptr - s->buffer : -1;
buf_size += s->buf_ptr - s->buffer + max_buffer_size;
s->buf_end = buffer + (s->buf_end - s->buffer);
s->buffer = buffer;
s->buffer_size = buf_size;
+ if (checksum_ptr_offset >= 0)
+ s->checksum_ptr = s->buffer + checksum_ptr_offset;
return 0;
}