From: Thomas Gleixner <tglx@linutronix.de>
Date: Tue, 1 Dec 2009 13:02:00 +0000 (+0100)
Subject: futex: Protect pid lookup in compat code with RCU
X-Git-Tag: v2.6.34-rc1~244^2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f409adf5b1db55ece7e80b67a944f9c0d3fe93e9;p=profile%2Fivi%2Fkernel-x86-ivi.git

futex: Protect pid lookup in compat code with RCU

find_task_by_vpid() in compat_sys_get_robust_list() does not require
tasklist_lock. It can be protected with rcu_read_lock as done in
sys_get_robust_list() already.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Darren Hart <dvhltc@us.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---

diff --git a/kernel/futex_compat.c b/kernel/futex_compat.c
index 2357165..d49afb2 100644
--- a/kernel/futex_compat.c
+++ b/kernel/futex_compat.c
@@ -146,7 +146,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 		struct task_struct *p;
 
 		ret = -ESRCH;
-		read_lock(&tasklist_lock);
+		rcu_read_lock();
 		p = find_task_by_vpid(pid);
 		if (!p)
 			goto err_unlock;
@@ -157,7 +157,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 		    !capable(CAP_SYS_PTRACE))
 			goto err_unlock;
 		head = p->compat_robust_list;
-		read_unlock(&tasklist_lock);
+		rcu_read_unlock();
 	}
 
 	if (put_user(sizeof(*head), len_ptr))
@@ -165,7 +165,7 @@ compat_sys_get_robust_list(int pid, compat_uptr_t __user *head_ptr,
 	return put_user(ptr_to_compat(head), head_ptr);
 
 err_unlock:
-	read_unlock(&tasklist_lock);
+	rcu_read_unlock();
 
 	return ret;
 }