ceph: fix recursion between ceph_set_acl() and __ceph_setattr()

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@gmail.com>
Signed-off-by: "Yan, Zheng" <zyan@redhat.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>
Tested-by: Luis Henriques <lhenriques@suse.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 10 insertions, 12 deletions

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index 12f2252f6c98..953275b651bc 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -2080,11 +2080,6 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
         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, struct iattr *attr)
              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, struct iattr *attr)
         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;
 }
 
 /*