lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20150502190117.778872891@linuxfoundation.org>
Date:	Sat,  2 May 2015 21:03:38 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>
Subject: [PATCH 3.14 83/92] RCU pathwalk breakage when running into a symlink overmounting something

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 3cab989afd8d8d1bc3d99fef0e7ed87c31e7b647 upstream.

Calling unlazy_walk() in walk_component() and do_last() when we find
a symlink that needs to be followed doesn't acquire a reference to vfsmount.
That's fine when the symlink is on the same vfsmount as the parent directory
(which is almost always the case), but it's not always true - one _can_
manage to bind a symlink on top of something.  And in such cases we end up
with excessive mntput().

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/namei.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1545,7 +1545,8 @@ static inline int walk_component(struct
 
 	if (should_follow_link(path->dentry, follow)) {
 		if (nd->flags & LOOKUP_RCU) {
-			if (unlikely(unlazy_walk(nd, path->dentry))) {
+			if (unlikely(nd->path.mnt != path->mnt ||
+				     unlazy_walk(nd, path->dentry))) {
 				err = -ECHILD;
 				goto out_err;
 			}
@@ -2992,7 +2993,8 @@ finish_lookup:
 
 	if (should_follow_link(path->dentry, !symlink_ok)) {
 		if (nd->flags & LOOKUP_RCU) {
-			if (unlikely(unlazy_walk(nd, path->dentry))) {
+			if (unlikely(nd->path.mnt != path->mnt ||
+				     unlazy_walk(nd, path->dentry))) {
 				error = -ECHILD;
 				goto out;
 			}


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ