From: Al Viro <viro@zeniv.linux.org.uk>
Date: Sun, 28 Feb 2016 00:23:16 +0000 (-0500)
Subject: namei: ->d_inode of a pinned dentry is stable only for positives
X-Git-Tag: v4.1.12-92~150^2~149
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=e640f78a8d1bae768328da5d35ffefa30c428472;p=users%2Fjedix%2Flinux-maple.git

namei: ->d_inode of a pinned dentry is stable only for positives

Orabug: 23330981

[ Upstream commit d4565649b6d6923369112758212b851adc407f0c ]

both do_last() and walk_component() risk picking a NULL inode out
of dentry about to become positive, *then* checking its flags and
seeing that it's not negative anymore and using (already stale by
then) value they'd fetched earlier.  Usually ends up oopsing soon
after that...

Cc: stable@vger.kernel.org # v3.13+
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
(cherry picked from commit 9b77cd137fd841d7a14e1c9428cfc49f4df0306e)

Signed-off-by: Dan Duval <dan.duval@oracle.com>
---

diff --git a/fs/namei.c b/fs/namei.c
index 438572278a9e3..f3cc848da8bc4 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1619,10 +1619,10 @@ static inline int walk_component(struct nameidata *nd, struct path *path,
 		if (err < 0)
 			goto out_err;
 
-		inode = path->dentry->d_inode;
 		err = -ENOENT;
 		if (d_is_negative(path->dentry))
 			goto out_path_put;
+		inode = path->dentry->d_inode;
 	}
 
 	if (should_follow_link(path->dentry, follow)) {
@@ -3078,6 +3078,7 @@ retry_lookup:
 		path_to_nameidata(path, nd);
 		goto out;
 	}
+	inode = path->dentry->d_inode;
 finish_lookup:
 	/* we _can_ be in RCU mode here */
 	if (should_follow_link(path->dentry, !symlink_ok)) {