rtmutex: avoid null derefence in WARN_ON
in [Kernel]
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From: Steven Rostedt on 9 Jul 2010 20:40 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(a)us.ibm.com> > Cc: Thomas Gleixner <tglx(a)linutronix.de> > Cc: Peter Zijlstra <peterz(a)infradead.org> > Cc: Ingo Molnar <mingo(a)elte.hu> > Cc: Eric Dumazet <eric.dumazet(a)gmail.com> > Cc: John Kacur <jkacur(a)redhat.com> > Cc: Steven Rostedt <rostedt(a)goodmis.org> > Cc: Mike Galbraith <efault(a)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. The below, well yeah. -- Steve > + WARN_ON(pendowner->pi_blocked_on->lock != lock); > + } > > pendowner->pi_blocked_on = NULL; > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Darren Hart on 10 Jul 2010 10:50
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(a)us.ibm.com> >> Cc: Thomas Gleixner<tglx(a)linutronix.de> >> Cc: Peter Zijlstra<peterz(a)infradead.org> >> Cc: Ingo Molnar<mingo(a)elte.hu> >> Cc: Eric Dumazet<eric.dumazet(a)gmail.com> >> Cc: John Kacur<jkacur(a)redhat.com> >> Cc: Steven Rostedt<rostedt(a)goodmis.org> >> Cc: Mike Galbraith<efault(a)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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |