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authorWaiman Long <longman@redhat.com>2019-07-20 18:04:10 +0300
committerIngo Molnar <mingo@kernel.org>2019-07-25 16:39:22 +0300
commit78134300579a45f527ca173ec8fdb4701b69f16e (patch)
tree976f25693137d6c6d3a0e86693f8ce2c45d543d4 /kernel
parentf9adc23ee91e6f561bb70c6147d8d45bd164d62f (diff)
downloadlinux-78134300579a45f527ca173ec8fdb4701b69f16e.tar.xz
locking/rwsem: Don't call owner_on_cpu() on read-owner
For writer, the owner value is cleared on unlock. For reader, it is left intact on unlock for providing better debugging aid on crash dump and the unlock of one reader may not mean the lock is free. As a result, the owner_on_cpu() shouldn't be used on read-owner as the task pointer value may not be valid and it might have been freed. That is the case in rwsem_spin_on_owner(), but not in rwsem_can_spin_on_owner(). This can lead to use-after-free error from KASAN. For example, BUG: KASAN: use-after-free in rwsem_down_write_slowpath (/home/miguel/kernel/linux/kernel/locking/rwsem.c:669 /home/miguel/kernel/linux/kernel/locking/rwsem.c:1125) Fix this by checking for RWSEM_READER_OWNED flag before calling owner_on_cpu(). Reported-by: Luis Henriques <lhenriques@suse.com> Tested-by: Luis Henriques <lhenriques@suse.com> Signed-off-by: Waiman Long <longman@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jeff Layton <jlayton@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tim Chen <tim.c.chen@linux.intel.com> Cc: Will Deacon <will.deacon@arm.com> Cc: huang ying <huang.ying.caritas@gmail.com> Fixes: 94a9717b3c40e ("locking/rwsem: Make rwsem->owner an atomic_long_t") Link: https://lkml.kernel.org/r/81e82d5b-5074-77e8-7204-28479bbe0df0@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/locking/rwsem.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 37524a47f002..bc91aacaab58 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -666,7 +666,11 @@ static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem,
preempt_disable();
rcu_read_lock();
owner = rwsem_owner_flags(sem, &flags);
- if ((flags & nonspinnable) || (owner && !owner_on_cpu(owner)))
+ /*
+ * Don't check the read-owner as the entry may be stale.
+ */
+ if ((flags & nonspinnable) ||
+ (owner && !(flags & RWSEM_READER_OWNED) && !owner_on_cpu(owner)))
ret = false;
rcu_read_unlock();
preempt_enable();