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Subject[tip: locking/core] futex: Reorder sanity checks in futex_requeue()
The following commit has been merged into the locking/core branch of tip:

Commit-ID: d69cba5c719b0c551f6380ec5da4ed8c20a3815a
Gitweb: https://git.kernel.org/tip/d69cba5c719b0c551f6380ec5da4ed8c20a3815a
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Sun, 15 Aug 2021 23:29:15 +02:00
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 17 Aug 2021 19:05:54 +02:00

futex: Reorder sanity checks in futex_requeue()

No point in allocating memory when the input parameters are bogus.
Validate all parameters before proceeding.

Suggested-by: Davidlohr Bueso <dave@stgolabs.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210815211305.581789253@linutronix.de
---
kernel/futex.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 8d8bad5..a5232f6 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1934,13 +1934,6 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
return -EINVAL;

/*
- * requeue_pi requires a pi_state, try to allocate it now
- * without any locks in case it fails.
- */
- if (refill_pi_state_cache())
- return -ENOMEM;
-
- /*
* futex_requeue() allows the caller to define the number
* of waiters to wake up via the @nr_wake argument. With
* REQUEUE_PI, waking up more than one waiter is creating
@@ -1963,6 +1956,13 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags,
*/
if (nr_wake != 1)
return -EINVAL;
+
+ /*
+ * requeue_pi requires a pi_state, try to allocate it now
+ * without any locks in case it fails.
+ */
+ if (refill_pi_state_cache())
+ return -ENOMEM;
}

retry:
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