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[4.2.y-ckt,217/273] should_follow_link(): validate ->d_seq after having decided to follow

Message ID 1457391064-6660-218-git-send-email-kamal@canonical.com
State New
Headers show

Commit Message

Kamal Mostafa March 7, 2016, 10:50 p.m. UTC 
4.2.8-ckt5 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Al Viro <viro@zeniv.linux.org.uk>

commit a7f775428b8f5808815c0e3004020cedb94cbe3b upstream.

... otherwise d_is_symlink() above might have nothing to do with
the inode value we've got.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 fs/namei.c | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/fs/namei.c b/fs/namei.c
index 1047096..414561f 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1714,6 +1714,11 @@  static inline int should_follow_link(struct nameidata *nd, struct path *link,
 		return 0;
 	if (!follow)
 		return 0;
+	/* make sure that d_is_symlink above matches inode */
+	if (nd->flags & LOOKUP_RCU) {
+		if (read_seqcount_retry(&link->dentry->d_seq, seq))
+			return -ECHILD;
+	}
 	return pick_link(nd, link, inode, seq);
 }