On 2019-05-29, Olga Kornievskaia <aglo@xxxxxxxxx> wrote: > On Wed, May 29, 2019 at 1:14 PM Trond Myklebust <trondmy@xxxxxxxxxxxxxxx> > wrote: >> >> On Wed, 2019-05-29 at 11:10 -0400, Nick Bowler wrote: >> > Hi, >> > >> > I upgraded to Linux 5.1.5 on one machine yesterday, and this morning >> > I happened noticed a large amount of backtraces in the log. It appears >> > that the system oopsed 62 times over a period of about 5 minutes, >> > producing about half a megabyte of log messages, after which the >> > messages stopped. No idea what action (if any) triggered these. >> > >> > However, other than the noise in the logs there is nothing obviously >> > broken, but I thought I should report the spews anyway. I was >> > running 5.0.9 previously and have not seen any similar errors. The >> > first couple spews are appended. All 64 faults look very similar >> > to these ones, with the same faulting address and the same >> > rpc_check_timeout function at the top of the backtrace. >> >> 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). Cheers, Nick
