----- Original Message ----- > From: "Steven Rostedt" <rost...@goodmis.org> > To: "Mathieu Desnoyers" <mathieu.desnoy...@efficios.com> > Cc: linux-kernel@vger.kernel.org, "Sasha Levin" <sasha.le...@oracle.com>, > "Oleg Nesterov" <o...@redhat.com>, "Dave > Jones" <da...@redhat.com> > Sent: Thursday, May 8, 2014 9:05:20 AM > Subject: Re: [PATCH] Fix: tracepoint: use after rcu free > > On Thu, 8 May 2014 07:47:49 -0400 > Mathieu Desnoyers <mathieu.desnoy...@efficios.com> wrote: > > > commit de7b2973903c6cc50b31ee5682a69b2219b9919d > > Author: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > > Date: Tue Apr 8 17:26:21 2014 -0400 > > Hi Mathieu, > > Thanks for the quick fix. > > > > > > tracepoint: Use struct pointer instead of name hash for reg/unreg > > tracepoints > > > > introduces a use after free by calling release_probes on the old struct > > Note when talking about commits already in mainline, use the first 12 > characters of the commit sha1 followed by the subject. Like so: > > Commit de7b2973903c "tracepoint: Use struct pointer instead of name > hash for reg/unreg tracepoints" introduces a use after free ...
OK, will do. > > > > tracepoint array before the newly allocated array is published with > > rcu_assign_pointer. There is a race window where tracepoints (RCU > > readers) can perform a "use-after-grace-period-after-free", which shows > > up as a GPF in stress-tests. > > > > Link: https://lkml.org/lkml/2014/5/6/738 > > Also, Link tags need to point to lkml.kernel.org. > > Link: http://lkml.kernel.org/r/53698021.5020...@oracle.com > > Which is "lkml.kernel.org/r/" followed by the Message-ID. OK > > We can also include a (even though it's redundant) > > Fixes: de7b2973903c "tracepoint: Use struct pointer instead of name hash for > reg/unreg tracepoints" Thanks for the pointers, I'll keep those in mind for my next patches. > > I'll update the change log to reflect my comments and then pull this > into my urgent branch and start testing it. Thanks! Mathieu > > Thanks, > > -- Steve > > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > > CC: Steven Rostedt <rost...@goodmis.org> > > CC: Sasha Levin <sasha.le...@oracle.com> > > CC: Oleg Nesterov <o...@redhat.com> > > CC: Dave Jones <da...@redhat.com> > > --- > > kernel/tracepoint.c | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c > > index ac5b23c..6620e58 100644 > > --- a/kernel/tracepoint.c > > +++ b/kernel/tracepoint.c > > @@ -188,7 +188,6 @@ static int tracepoint_add_func(struct tracepoint *tp, > > WARN_ON_ONCE(1); > > return PTR_ERR(old); > > } > > - release_probes(old); > > > > /* > > * rcu_assign_pointer has a smp_wmb() which makes sure that the new > > @@ -200,6 +199,7 @@ static int tracepoint_add_func(struct tracepoint *tp, > > rcu_assign_pointer(tp->funcs, tp_funcs); > > if (!static_key_enabled(&tp->key)) > > static_key_slow_inc(&tp->key); > > + release_probes(old); > > return 0; > > } > > > > @@ -221,7 +221,6 @@ static int tracepoint_remove_func(struct tracepoint > > *tp, > > WARN_ON_ONCE(1); > > return PTR_ERR(old); > > } > > - release_probes(old); > > > > if (!tp_funcs) { > > /* Removed last function */ > > @@ -232,6 +231,7 @@ static int tracepoint_remove_func(struct tracepoint > > *tp, > > static_key_slow_dec(&tp->key); > > } > > rcu_assign_pointer(tp->funcs, tp_funcs); > > + release_probes(old); > > return 0; > > } > > > > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
