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

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.

Cc: stable@vger.kernel.org # needs backporting for < 4.9
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>

diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index d449e1c03cbd791922148ad00c3d6d0f0e1599ce..d3119fe3ab45fdbdb534651ef68194815dcc544b 100644 (file)
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -2071,11 +2071,6 @@ 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;
@@ -2088,14 +2083,12 @@ int __ceph_setattr(struct inode *inode, struct iattr *attr)
        dout("setattr %p result=%d (%s locally, %d remote)\n", inode, err,
             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;
 }
 
@@ -2114,7 +2107,12 @@ 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;
 }
 
 /*