On 2019-06-03, Nick Bowler <nbowler@xxxxxxxxxx> wrote: > On 2019-05-29, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: >> On Wed, May 29, 2019 at 1:14 PM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> >>> OK, I think this is the same problem that Olga was seeing (Cced), and >>> it looks like I missed the use-after-free issue when the server returns >>> a credential error when she asked. >> >> I think this is actually different than what I encountered for the >> umount case but the trigger is the same -- failing validation. >> >> I tried to reproduce Nick's oops on 5.2-rc but haven't been able to >> (but I'm not confident I produced the right trigger conditions. will >> try 5.1). > > OK, I think I found something that triggers this fault. This happens > when certain local users try to stat a file or directory on an nfs > mount. Presumably these UIDs do not have appropriate permissions on > the server but I'm not sure exactly (I do not control the server). > > I can reproduce the oops with a command like this: > > # su -s/bin/sh -c 'stat /path/to/nfs/file' problematic_user > > which oopes every time (and SIGKILLs the stat command). (I have not yet > rebooted since the original report or tried with Trond's patch applied. > I will do that next, and also try 5.1.6). OK, armed with this reproducer I can confirm that the issue is still present in 5.1.6, and that applying Trond's patch on top of 5.1.6 appears to fix the problem. Thanks, Nick
