On Fri, Feb 10, 2017 at 9:59 AM, Eric Dumazet <eric.duma...@gmail.com> wrote: > On Fri, 2017-02-10 at 09:49 -0800, Cong Wang wrote: >> On Thu, Feb 9, 2017 at 7:23 PM, Eric Dumazet <eric.duma...@gmail.com> wrote: >> > On Thu, 2017-02-09 at 19:19 -0800, Eric Dumazet wrote: >> > >> >> More likely the bug is in fanout_add(), with a buggy sequence in error >> >> case, and not correct locking. >> >> >> >> kfree(po->rollover); >> >> po->rollover = NULL; >> >> >> >> Two cpus entering fanout_add() (using the same af_packet socket, >> >> syzkaller courtesy...) might both see po->fanout being NULL. >> >> >> >> Then they grab the mutex. Too late... >> > >> > Patch could be : >> > >> >> For me, clearly the data structure that use-after-free'd is struct sock >> rather than struct packet_rollover. > > Fine. But your patch makes absolutely no sense.
I don't have to give a 100% correct patch to prove my explanation of the crash. At least it makes more sense than yours...
