Messages in this thread | | | Date | Sat, 10 Jul 2010 07:42:45 -0700 | From | Darren Hart <> | Subject | Re: [PATCH 1/4] rtmutex: avoid null derefence in WARN_ON |
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On 07/09/2010 05:29 PM, Steven Rostedt wrote: > On Fri, 2010-07-09 at 15:32 -0700, Darren Hart wrote: >> If the pi_blocked_on variable is NULL, the subsequent WARN_ON's >> will cause an OOPS. Only perform the susequent checks if >> pi_blocked_on is valid. >> >> Signed-off-by: Darren Hart<dvhltc@us.ibm.com> >> Cc: Thomas Gleixner<tglx@linutronix.de> >> Cc: Peter Zijlstra<peterz@infradead.org> >> Cc: Ingo Molnar<mingo@elte.hu> >> Cc: Eric Dumazet<eric.dumazet@gmail.com> >> Cc: John Kacur<jkacur@redhat.com> >> Cc: Steven Rostedt<rostedt@goodmis.org> >> Cc: Mike Galbraith<efault@gmx.de> >> --- >> kernel/rtmutex.c | 7 ++++--- >> 1 files changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c >> index 23dd443..baac7d9 100644 >> --- a/kernel/rtmutex.c >> +++ b/kernel/rtmutex.c >> @@ -579,9 +579,10 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate) >> >> raw_spin_lock(&pendowner->pi_lock); >> >> - WARN_ON(!pendowner->pi_blocked_on); >> - WARN_ON(pendowner->pi_blocked_on != waiter); >> - WARN_ON(pendowner->pi_blocked_on->lock != lock); >> + if (!WARN_ON(!pendowner->pi_blocked_on)) { >> + WARN_ON(pendowner->pi_blocked_on != waiter); > > The above actually has no issue if the pi_blocked_on is NULL.
It doesn't, but it's also redundant and makes the console noisier for no reason. Seemed worth while to drop it under the if in the same go.
-- Darren
> The below, well yeah. > > -- Steve > >> + WARN_ON(pendowner->pi_blocked_on->lock != lock); >> + } >> >> pendowner->pi_blocked_on = NULL; >> > >
-- Darren Hart IBM Linux Technology Center Real-Time Linux Team
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