On Wed, Apr 05, 2017 at 01:29:19AM +0800, Xin Long wrote: > On Tue, Apr 4, 2017 at 9:28 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > Hi, > > > > I've got the following error report while fuzzing the kernel with syzkaller. > > > > On commit a71c9a1c779f2499fb2afc0553e543f18aff6edf (4.11-rc5). > > > > A reproducer and .config are attached. > The script is pretty hard to reproduce the issue in my env. I didn't try running it but I also found the reproducer very complicated to follow. Do you have any plans on having some PoC optimizer, so we can have a more readable code? strace is handy for filtering the noise, yes, but sometimes it doesn't cut it. > But there seems a case to cause a use-after-free when out of snd_buf. > > the case is like: > ----------- > one thread: another thread: > sctp_rcv hold asoc (hold transport) > enqueue the chunk to backlog queue > [refcnt=2] > > sctp_close free assoc > [refcnt=1] > > sctp_sendmsg find asoc > but not hold it > > out of snd_buf > hold asoc, schedule out > [refcnt = 2] > > process backlog and put asoc/transport > [refcnt=1] > > schedule in, put asoc > [refcnt=0] <--- destroyed > > sctp_sendmsg continue It shouldn't be continuing here because sctp_wait_for_sndbuf and sctp_wait_for_connect functions are checking if the asoc is dead already when it schedules in, even though sctp_wait_for_connect return value is ignored and sctp_sendmsg() simply returns after that. Or the checks for dead asocs in there aren't enough somehow. > using asoc, panic -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
