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* [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state()
@ 2020-11-06  8:52 Dan Carpenter
  2020-11-09 11:21 ` Peter Zijlstra
  2020-11-09 13:34 ` [tip: locking/urgent] " tip-bot2 for Dan Carpenter
  0 siblings, 2 replies; 3+ messages in thread
From: Dan Carpenter @ 2020-11-06  8:52 UTC (permalink / raw)
  To: Peter Zijlstra, Thomas Gleixner
  Cc: Ingo Molnar, Darren Hart, linux-kernel, kernel-janitors

The exit_pi_state_list() function calls put_pi_state() with IRQs
disabled and is not expecting that IRQs will be enabled inside the
function.  Use the _irqsave() so that IRQs are restored to the original
state instead of enabled unconditionally.

Fixes: 153fbd1226fb ("futex: Fix more put_pi_state() vs. exit_pi_state_list() races")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
This is from static analysis and not tested.  I am not very familiar
with futex code.

 kernel/futex.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index f8614ef4ff31..ca84745713bc 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -788,8 +788,9 @@ static void put_pi_state(struct futex_pi_state *pi_state)
 	 */
 	if (pi_state->owner) {
 		struct task_struct *owner;
+		unsigned long flags;
 
-		raw_spin_lock_irq(&pi_state->pi_mutex.wait_lock);
+		raw_spin_lock_irqsave(&pi_state->pi_mutex.wait_lock, flags);
 		owner = pi_state->owner;
 		if (owner) {
 			raw_spin_lock(&owner->pi_lock);
@@ -797,7 +798,7 @@ static void put_pi_state(struct futex_pi_state *pi_state)
 			raw_spin_unlock(&owner->pi_lock);
 		}
 		rt_mutex_proxy_unlock(&pi_state->pi_mutex, owner);
-		raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
+		raw_spin_unlock_irqrestore(&pi_state->pi_mutex.wait_lock, flags);
 	}
 
 	if (current->pi_state_cache) {
-- 
2.28.0


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2020-11-06  8:52 [PATCH] futex: Don't enable IRQs unconditionally in put_pi_state() Dan Carpenter
2020-11-09 11:21 ` Peter Zijlstra
2020-11-09 13:34 ` [tip: locking/urgent] " tip-bot2 for Dan Carpenter

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