Messages in this thread Patch in this message | | | Date | Thu, 29 May 2014 09:57:23 +0200 | From | Peter Zijlstra <> | Subject | Re: perf: use after free in perf_remove_from_context |
| |
On Wed, May 28, 2014 at 07:52:07PM -0400, Sasha Levin wrote: > On 05/14/2014 12:35 PM, Peter Zijlstra wrote: > > On Wed, May 14, 2014 at 12:32:26PM -0400, Sasha Levin wrote: > >> > -----BEGIN PGP SIGNED MESSAGE----- > >> > Hash: SHA1 > >> > > >> > On 05/14/2014 12:29 PM, Peter Zijlstra wrote: > >>> > > On Mon, May 12, 2014 at 11:42:33AM -0400, Sasha Levin wrote: > >>>> > >> Hi all, > >>>> > >> > >>>> > >> While fuzzing with trinity inside a KVM tools guest running the latest -next kernel I've stumbled on the following spew. Maybe related to the very recent change in freeing on task exit? > >>>> > >> > >>>> > >> [ 2509.827261] general protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC [ 2509.830379] Dumping ftrace buffer: [ 2509.830379] (ftrace buffer empty) [ 2509.830379] Modules linked in: [ 2509.830379] CPU: 47 PID: 43306 Comm: trinity-c126 Tainted: G W 3.15.0-rc5-next-20140512-sasha-00019-ga20bc00-dirty #456 > >>> > > > >>> > > Any particular trinity setup? And would you happen to have the seed of that run? > >> > > >> > Nothing special about trinity options. 400 threads and blacklisting some of the > >> > destructive syscalls (umount, reboot, etc). > >> > > >> > I don't have the seed, but that problem did reproduce again tonight so I can test > >> > out debug code if you have something in mind. > > Nah, I drew a pretty big blank, which is why I wanted to see if I could > > reproduce. If you could share your trinity cmdline I'd be much obliged. > > While I did manage to clone (the repo moved since last time) and build > > it, I'm not really that handy with it and want to avoid destroying my > > machine if possible ;-) > > Anything I could do to help out with this? It reproduces pretty easily on my > configuration so I'd be happy to test out whatever might help.
Yeah, it takes me days to test anything, and my last guess panned out to nothing, at which point I decided I needed to look at the things I'd neglected for a bit :/
Could you see if the below makes any difference? I'll try and get back to tracking this.
--- kernel/events/core.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 9efb1e7858ac..851dc9dc5643 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7497,8 +7497,10 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) */ mutex_lock(&child_ctx->mutex); + rcu_read_lock(); list_for_each_entry_rcu(child_event, &child_ctx->event_list, event_entry) __perf_event_exit_task(child_event, child_ctx, child); + rcu_read_unlock(); mutex_unlock(&child_ctx->mutex); [unhandled content-type:application/pgp-signature] | |