[PATCH] unshare: Use rcu_assign_pointer when setting sighand

The sighand pointer only needs the rcu_read_lock on the
read side.  So only depending on task_lock protection
when setting this pointer is not enough.  We also need
a memory barrier to ensure the initialization is seen first.

Use rcu_assign_pointer as it does this for us, and clearly
documents that we are setting an rcu readable pointer.

Signed-off-by: Eric W. Biederman <[email protected]>


---

 kernel/fork.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

f0cdb649b7140927777f4355631648b396ee235b
diff --git a/kernel/fork.c b/kernel/fork.c
index d2706e9..2f24553 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1573,7 +1573,7 @@ asmlinkage long sys_unshare(unsigned lon
 
 		if (new_sigh) {
 			sigh = current->sighand;
-			current->sighand = new_sigh;
+			rcu_assign_pointer(current->sighand, new_sigh);
 			new_sigh = sigh;
 		}
 
-- 
1.2.4.g2d33

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---

• Follow-Ups:
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    • From: "Paul E. McKenney" <[email protected]>

• References:
  • [PATCH] unshare: Cleanup up the sys_unshare interface before we are committed.
    • From: [email protected] (Eric W. Biederman)

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