Em Tue, Dec 05, 2017 at 05:11:56PM +0900, Namhyung Kim escreveu: > Hello, > > On Thu, Nov 30, 2017 at 04:37:12PM -0300, Arnaldo Carvalho de Melo wrote: > > Em Thu, Nov 30, 2017 at 09:20:26AM +0100, Peter Zijlstra escreveu: > > > On Thu, Nov 30, 2017 at 10:32:19AM +0800, Fengguang Wu wrote: > > > > Hello, > > > > > > > > FYI this happens in mainline kernel 4.15.0-rc1. > > > > It looks like a new regression and hard to bisect. > > > > > > > > It occurs in 1 out of 57 boots. > > > > > > > > [ 10.009610] chown (367) used greatest stack depth: 26944 bytes left > > > > Kernel tests: Boot OK! > > > > [ 30.357729] trinity-main uses obsolete (PF_INET,SOCK_PACKET) > > > > [ 31.301433] sock: process `trinity-main' is using obsolete > > > > setsockopt SO_BSDCOMPAT > > > > [ 31.310289] > > > > ================================================================== > > > > [ 31.311490] BUG: KASAN: slab-out-of-bounds in > > > > perf_callchain_user+0x494/0x530: > > > > perf_callchain_store at > > > > include/linux/perf_event.h:1128 > > > > (inlined by) > > > > perf_callchain_user at arch/x86/events/core.c:2485 > > > > > > I don't think we recently changed anything here... > > > > > > But I do have vague memories of something being off here; I never quite > > > could penetrate the max_stack / contexts_maxed stuff, and istr acme was > > > going to have a peek. > > > > Sure, but I saw some backward ring buffer stuff in there as well, no? > > IIRC that came after the max-stack code, Adding Wang to the CC list. > > I think it's because of per-event max-stack not being checked for the > first event. Please see the patch below..
Argh, well spotted, Acked-by: Arnaldo Carvalho de Melo <[email protected]> > Also I'm not sure that the allocation failure check would work > correctly since it decrements nr_callchain_events when it fails. Can you elaborate a bit more? > Thanks, > Namhyung > > > > >From c12126c4ff9835f0899619db3ee7b4a3151ff2bb Mon Sep 17 00:00:00 2001 > From: Namhyung Kim <[email protected]> > Date: Tue, 5 Dec 2017 16:54:50 +0900 > Subject: [PATCH] perf/core: Fix overflow on perf_callchain_entry > > The commit 97c79a38cd45 add a check whether per-event max stack is > greater than the global max. But it missed to do it for the first > event. So if the event had a stack depth greater than the global max, > it could overflow the callchain entry list. > > Reported-by: Fengguang Wu <[email protected]> > Fixes: 97c79a38cd45 ("perf core: Per event callchain limit") > Signed-off-by: Namhyung Kim <[email protected]> > --- > kernel/events/callchain.c | 21 ++++++++++++--------- > 1 file changed, 12 insertions(+), 9 deletions(-) > > diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c > index 1b2be63c8528..e449e23802eb 100644 > --- a/kernel/events/callchain.c > +++ b/kernel/events/callchain.c > @@ -119,19 +119,22 @@ int get_callchain_buffers(int event_max_stack) > goto exit; > } > > + /* > + * If requesting per event more than the global cap, > + * return a different error to help userspace figure this out. > + * > + * And also do it here so that we have &callchain_mutex held. > + */ > + if (event_max_stack > sysctl_perf_event_max_stack) { > + err = -EOVERFLOW; > + goto exit; > + } > + > if (count > 1) { > /* If the allocation failed, give up */ > if (!callchain_cpus_entries) > err = -ENOMEM; > - /* > - * If requesting per event more than the global cap, > - * return a different error to help userspace figure > - * this out. > - * > - * And also do it here so that we have &callchain_mutex held. > - */ > - if (event_max_stack > sysctl_perf_event_max_stack) > - err = -EOVERFLOW; > + > goto exit; > } > > -- > 2.15.0
