linux-kernel - [PATCH 4.9 50/54] ceph: fix recursion between ceph_set_acl() and __ceph

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Message-Id: <20170501212633.801555783@linuxfoundation.org>
Date:   Mon,  1 May 2017 14:31:57 -0700
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jerry Lee <leisurelysw24@...il.com>,
        "Yan, Zheng" <zyan@...hat.com>, Jeff Layton <jlayton@...hat.com>,
        Luis Henriques <lhenriques@...e.com>,
        Ilya Dryomov <idryomov@...il.com>
Subject: [PATCH 4.9 50/54] ceph: fix recursion between ceph_set_acl() and __ceph_setattr()

4.9-stable 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/ceph/inode.c |   22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -2080,11 +2080,6 @@ int __ceph_setattr(struct inode *inode,
 	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;
@@ -2098,13 +2093,11 @@ int __ceph_setattr(struct inode *inode,
 	     ceph_cap_string(dirtied), mask);
 
 	ceph_mdsc_put_request(req);
-	if (mask & CEPH_SETATTR_SIZE)
-		__ceph_do_pending_vmtruncate(inode);
-	ceph_free_cap_flush(prealloc_cf);
-	return err;
-out_put:
-	ceph_mdsc_put_request(req);
 	ceph_free_cap_flush(prealloc_cf);
+
+	if (err >= 0 && (mask & CEPH_SETATTR_SIZE))
+		__ceph_do_pending_vmtruncate(inode);
+
 	return err;
 }
 
@@ -2123,7 +2116,12 @@ int ceph_setattr(struct dentry *dentry,
 	if (err != 0)
 		return err;
 
-	return __ceph_setattr(inode, attr);
+	err = __ceph_setattr(inode, attr);
+
+	if (err >= 0 && (attr->ia_valid & ATTR_MODE))
+		err = posix_acl_chmod(inode, attr->ia_mode);
+
+	return err;
 }
 
 /*