[PATCH] ceph: fix recursively call between ceph_set_acl and __ceph_setattr

["Yan, Zheng" <zyan@redhat.com>]

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 it's 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>
---
 fs/ceph/acl.c   |  4 ++--
 fs/ceph/inode.c | 24 +++++++++++-------------
 fs/ceph/super.h |  3 ++-
 3 files changed, 15 insertions(+), 16 deletions(-)

diff --git a/fs/ceph/acl.c b/fs/ceph/acl.c
index 987044b..bc985e0 100644
--- a/fs/ceph/acl.c
+++ b/fs/ceph/acl.c
@@ -133,7 +133,7 @@ int ceph_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 	if (new_mode != old_mode) {
 		newattrs.ia_mode = new_mode;
 		newattrs.ia_valid = ATTR_MODE;
-		ret = __ceph_setattr(inode, &newattrs);
+		ret = __ceph_setattr(inode, &newattrs, false);
 		if (ret)
 			goto out_free;
 	}
@@ -143,7 +143,7 @@ int ceph_set_acl(struct inode *inode, struct posix_acl *acl, int type)
 		if (new_mode != old_mode) {
 			newattrs.ia_mode = old_mode;
 			newattrs.ia_valid = ATTR_MODE;
-			__ceph_setattr(inode, &newattrs);
+                       __ceph_setattr(inode, &newattrs, false);
 		}
 		goto out_free;
 	}
diff --git a/fs/ceph/inode.c b/fs/ceph/inode.c
index efee88c..4aa23c6 100644
--- a/fs/ceph/inode.c
+++ b/fs/ceph/inode.c
@@ -1885,7 +1885,7 @@ static const struct inode_operations ceph_symlink_iops = {
 	.listxattr = ceph_listxattr,
 };
 
-int __ceph_setattr(struct inode *inode, struct iattr *attr)
+int __ceph_setattr(struct inode *inode, struct iattr *attr, bool update_acl)
 {
 	struct ceph_inode_info *ci = ceph_inode(inode);
 	const unsigned int ia_valid = attr->ia_valid;
@@ -2078,11 +2078,6 @@ 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;
@@ -2096,13 +2091,16 @@ 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) {
+		if (update_acl && (ia_valid & ATTR_MODE)) {
+			err = posix_acl_chmod(inode, attr->ia_mode);
+		}
+		if (mask & CEPH_SETATTR_SIZE) {
+			__ceph_do_pending_vmtruncate(inode);
+		}
+	}
 	return err;
 }
 
@@ -2121,7 +2119,7 @@ int ceph_setattr(struct dentry *dentry, struct iattr *attr)
 	if (err != 0)
 		return err;
 
-	return __ceph_setattr(inode, attr);
+       return __ceph_setattr(inode, attr, true);
 }
 
 /*
diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index 7334ee8..bc7769c 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -809,7 +809,8 @@ static inline int ceph_do_getattr(struct inode *inode, int mask, bool force)
 	return __ceph_do_getattr(inode, NULL, mask, force);
 }
 extern int ceph_permission(struct inode *inode, int mask);
-extern int __ceph_setattr(struct inode *inode, struct iattr *attr);
+extern int __ceph_setattr(struct inode *inode, struct iattr *attr,
+                         bool update_acl);
 extern int ceph_setattr(struct dentry *dentry, struct iattr *attr);
 extern int ceph_getattr(const struct path *path, struct kstat *stat,
 			u32 request_mask, unsigned int flags);
-- 
2.9.3