From: Romain Perier Date: Thu, 14 Apr 2016 13:36:03 +0000 (+0200) Subject: asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() X-Git-Tag: firefly_0821_release~176^2~4^2~48^2~128 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=4fad26a279caad671287e502e9b6d2487a56b270;p=firefly-linux-kernel-4.4.55.git asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() commit fba7cd681b6155e2d93e7862fcd6f970336b83c3 upstream. The recent decoupling of pagefault disable and preempt disable added an explicit preempt_disable/enable() pair to the futex_atomic_cmpxchg_inatomic() implementation in asm-generic/futex.h. But it forgot to add preempt_enable() calls to the error handling code pathes, which results in a preemption count imbalance. This is observable on boot when the test for atomic_cmpxchg() is calling futex_atomic_cmpxchg_inatomic() on a NULL pointer. Add the missing preempt_enable() calls to the error handling code pathes. [ tglx: Massaged changelog ] Fixes: d9b9ff8c1889 ("sched/preempt, futex: Disable preemption in UP futex_atomic_cmpxchg_inatomic() explicitly") Signed-off-by: Romain Perier Cc: linux-arch@vger.kernel.org Cc: Thomas Petazzoni Cc: Arnd Bergmann Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/1460640963-690-1-git-send-email-romain.perier@free-electrons.com Signed-off-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman --- diff --git a/include/asm-generic/futex.h b/include/asm-generic/futex.h index e56272c919b5..bf2d34c9d804 100644 --- a/include/asm-generic/futex.h +++ b/include/asm-generic/futex.h @@ -108,11 +108,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 val; preempt_disable(); - if (unlikely(get_user(val, uaddr) != 0)) + if (unlikely(get_user(val, uaddr) != 0)) { + preempt_enable(); return -EFAULT; + } - if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) + if (val == oldval && unlikely(put_user(newval, uaddr) != 0)) { + preempt_enable(); return -EFAULT; + } *uval = val; preempt_enable();