linux-kernel - [PATCH 3.16 171/178] ceph: fix recursion between ceph_set_acl() and __ceph

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: <lsq.1500213406.150956274@decadent.org.uk>
Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Luis Henriques" <lhenriques@...e.com>,
        "Yan, Zheng" <zyan@...hat.com>,
        "Jerry Lee" <leisurelysw24@...il.com>,
        "Ilya Dryomov" <idryomov@...il.com>,
        "Jeff Layton" <jlayton@...hat.com>
Subject: [PATCH 3.16 171/178] ceph: fix recursion between ceph_set_acl()
 and __ceph_setattr()

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

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

From: "Yan, Zheng" <zyan@...hat.com>

commit 8179a101eb5f4ef0ac9a915fcea9a9d3109efa90 upstream.

ceph_set_acl() calls __ceph_setattr() if the setacl operation needs
to modify inode's i_mode. __ceph_setattr() updates inode's i_mode,
then calls posix_acl_chmod().

The problem is that __ceph_setattr() calls posix_acl_chmod() before
sending the setattr request. The get_acl() call in posix_acl_chmod()
can trigger a getxattr request. The reply of the getxattr request
can restore inode's i_mode to its old value. The set_acl() call in
posix_acl_chmod() sees old value of inode's i_mode, so it calls
__ceph_setattr() again.

Link: http://tracker.ceph.com/issues/19688
Reported-by: Jerry Lee <leisurelysw24@...il.com>
Signed-off-by: "Yan, Zheng" <zyan@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...hat.com>
Tested-by: Luis Henriques <lhenriques@...e.com>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
[bwh: Backported to 3.16: All the changes are made in ceph_setattr() as
 there is no __ceph_setattr() function.]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1875,12 +1875,6 @@ int ceph_setattr(struct dentry *dentry,
 	if (inode_dirty_flags)
 		__mark_inode_dirty(inode, inode_dirty_flags);
 
-	if (ia_valid & ATTR_MODE) {
-		err = posix_acl_chmod(inode, attr->ia_mode);
-		if (err)
-			goto out_put;
-	}
-
 	if (mask) {
 		req->r_inode = inode;
 		ihold(inode);
@@ -1893,12 +1887,16 @@ int ceph_setattr(struct dentry *dentry,
 	     ceph_cap_string(dirtied), mask);
 
 	ceph_mdsc_put_request(req);
-	if (mask & CEPH_SETATTR_SIZE)
+
+	if (err >= 0 && (mask & CEPH_SETATTR_SIZE))
 		__ceph_do_pending_vmtruncate(inode);
+
+	if (err >= 0 && (attr->ia_valid & ATTR_MODE))
+		err = posix_acl_chmod(inode, attr->ia_mode);
+
 	return err;
 out:
 	spin_unlock(&ci->i_ceph_lock);
-out_put:
 	ceph_mdsc_put_request(req);
 	return err;
 }