From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 12 Sep 2013 18:57:01 +0000 (-0700)
Subject: vfs: don't copy things to user space holding the rcu readlock
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=ff812d724254b95df76b7775d1359d856927a840;p=openwrt%2Fstaging%2Fblogic.git

vfs: don't copy things to user space holding the rcu readlock

Oops.  That wasn't very smart.  We don't actually need the RCU lock any
more by the time we copy the cwd string to user space, but I had
stupidly surrounded the whole thing with it.

Introduced by commit 8b19e34188a3 ("vfs: make getcwd() get the root and
pwd path under rcu")

Is-a-big-hairy-idiot: Linus Torvalds <torvalds@linux-foundation.org>
---

diff --git a/fs/dcache.c b/fs/dcache.c
index 99d4d7226203..29d58212aaf0 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3067,6 +3067,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 		prepend(&cwd, &buflen, "\0", 1);
 		error = prepend_path(&pwd, &root, &cwd, &buflen);
 		br_read_unlock(&vfsmount_lock);
+		rcu_read_unlock();
 
 		if (error < 0)
 			goto out;
@@ -3087,10 +3088,10 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 		}
 	} else {
 		br_read_unlock(&vfsmount_lock);
+		rcu_read_unlock();
 	}
 
 out:
-	rcu_read_unlock();
 	free_page((unsigned long) page);
 	return error;
 }