* [PATCH 4.5 045/200] asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() [not found] <20160503000554.631204776@linuxfoundation.org> @ 2016-05-03 0:10 ` Greg Kroah-Hartman 2016-05-03 0:10 ` Greg Kroah-Hartman 0 siblings, 1 reply; 2+ messages in thread From: Greg Kroah-Hartman @ 2016-05-03 0:10 UTC (permalink / raw) To: linux-kernel Cc: Greg Kroah-Hartman, stable, Romain Perier, linux-arch, Thomas Petazzoni, Arnd Bergmann, Peter Zijlstra, Thomas Gleixner 4.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Romain Perier <romain.perier@free-electrons.com> 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 <romain.perier@free-electrons.com> Cc: linux-arch@vger.kernel.org Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1460640963-690-1-git-send-email-romain.perier@free-electrons.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- include/asm-generic/futex.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/include/asm-generic/futex.h +++ b/include/asm-generic/futex.h @@ -108,11 +108,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, 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(); ^ permalink raw reply [flat|nested] 2+ messages in thread
* [PATCH 4.5 045/200] asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() 2016-05-03 0:10 ` [PATCH 4.5 045/200] asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() Greg Kroah-Hartman @ 2016-05-03 0:10 ` Greg Kroah-Hartman 0 siblings, 0 replies; 2+ messages in thread From: Greg Kroah-Hartman @ 2016-05-03 0:10 UTC (permalink / raw) To: linux-kernel Cc: Greg Kroah-Hartman, stable, Romain Perier, linux-arch, Thomas Petazzoni, Arnd Bergmann, Peter Zijlstra, Thomas Gleixner 4.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Romain Perier <romain.perier@free-electrons.com> 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 <romain.perier@free-electrons.com> Cc: linux-arch@vger.kernel.org Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Cc: Arnd Bergmann <arnd@arndb.de> Cc: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/1460640963-690-1-git-send-email-romain.perier@free-electrons.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- include/asm-generic/futex.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/include/asm-generic/futex.h +++ b/include/asm-generic/futex.h @@ -108,11 +108,15 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, 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(); ^ permalink raw reply [flat|nested] 2+ messages in thread
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2016-05-03 0:10 ` [PATCH 4.5 045/200] asm-generic/futex: Re-enable preemption in futex_atomic_cmpxchg_inatomic() Greg Kroah-Hartman
2016-05-03 0:10 ` Greg Kroah-Hartman
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