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authorKirill Tkhai <ktkhai@virtuozzo.com>2017-06-16 16:44:34 +0300
committerIngo Molnar <mingo@kernel.org>2017-07-05 12:26:29 +0200
commita0c4acd2c220376b4e9690e75782d0c0afdaab9f (patch)
treee9a18f3565fa002ddc6b23a86a10f92eb8d86d81 /kernel
parent4422d80ed7d4bdb2d6e9fb890c66c3d9250ba694 (diff)
locking/rwsem-spinlock: Fix EINTR branch in __down_write_common()
If a writer could been woken up, the above branch if (sem->count == 0) break; would have moved us to taking the sem. So, it's not the time to wake a writer now, and only readers are allowed now. Thus, 0 must be passed to __rwsem_do_wake(). Next, __rwsem_do_wake() wakes readers unconditionally. But we mustn't do that if the sem is owned by writer in the moment. Otherwise, writer and reader own the sem the same time, which leads to memory corruption in callers. rwsem-xadd.c does not need that, as: 1) the similar check is made lockless there, 2) in __rwsem_mark_wake::try_reader_grant we test, that sem is not owned by writer. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: <stable@vger.kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Niklas Cassel <niklas.cassel@axis.com> Cc: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 17fcbd590d0c "locking/rwsem: Fix down_write_killable() for CONFIG_RWSEM_GENERIC_SPINLOCK=y" Link: http://lkml.kernel.org/r/149762063282.19811.9129615532201147826.stgit@localhost.localdomain Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/locking/rwsem-spinlock.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/locking/rwsem-spinlock.c b/kernel/locking/rwsem-spinlock.c
index c65f7989f850..20819df98125 100644
--- a/kernel/locking/rwsem-spinlock.c
+++ b/kernel/locking/rwsem-spinlock.c
@@ -231,8 +231,8 @@ int __sched __down_write_common(struct rw_semaphore *sem, int state)
out_nolock:
list_del(&waiter.list);
- if (!list_empty(&sem->wait_list))
- __rwsem_do_wake(sem, 1);
+ if (!list_empty(&sem->wait_list) && sem->count >= 0)
+ __rwsem_do_wake(sem, 0);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);
return -EINTR;