On Wed, 2013-12-11 at 17:04 +0000, Tvrtko Ursulin wrote: > Hi all, > > It seems that the buffer allocation in seq_read can double in size > indefinitely, at least I've seen that in practice with /proc/<pid>/smaps > (attempting to double m->size to 4M on a read of 1000 bytes). This > produces an ugly WARN_ON_ONCE, which should perhaps be avoided? (given > that it can be triggered by userspace at will) > > From the top comment in seq_file.c one would think that it is a > fundamental limitation of the current code that everything which will be > read (even if in chunks) needs to be in the kernel side buffer at the > same time? Oh-oh, seems that m->size is doubled on every read. So if app is reading with a buffer smaller than data available, it can do nine reads before it hits a >MAX_ORDER allocation. Not good. :) Regards, Tvrtko -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
