linux-kernel - [PATCH AUTOSEL 5.10 11/13] ceph: fix deadlock or deadcode of misusing dget()

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Date: Sun, 28 Jan 2024 11:15:57 -0500
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Xiubo Li <xiubli@...hat.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Jeff Layton <jlayton@...nel.org>,
	Ilya Dryomov <idryomov@...il.com>,
	Sasha Levin <sashal@...nel.org>,
	ceph-devel@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 11/13] ceph: fix deadlock or deadcode of misusing dget()

From: Xiubo Li <xiubli@...hat.com>

[ Upstream commit b493ad718b1f0357394d2cdecbf00a44a36fa085 ]

The lock order is incorrect between denty and its parent, we should
always make sure that the parent get the lock first.

But since this deadcode is never used and the parent dir will always
be set from the callers, let's just remove it.

Link: https://lore.kernel.org/r/20231116081919.GZ1957730@ZenIV
Reported-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Xiubo Li <xiubli@...hat.com>
Reviewed-by: Jeff Layton <jlayton@...nel.org>
Signed-off-by: Ilya Dryomov <idryomov@...il.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/ceph/caps.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index 432dc2a16e28..b0cf79b0dc49 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -4598,12 +4598,14 @@ int ceph_encode_dentry_release(void **p, struct dentry *dentry,
 			       struct inode *dir,
 			       int mds, int drop, int unless)
 {
-	struct dentry *parent = NULL;
 	struct ceph_mds_request_release *rel = *p;
 	struct ceph_dentry_info *di = ceph_dentry(dentry);
 	int force = 0;
 	int ret;
 
+	/* This shouldn't happen */
+	BUG_ON(!dir);
+
 	/*
 	 * force an record for the directory caps if we have a dentry lease.
 	 * this is racy (can't take i_ceph_lock and d_lock together), but it
@@ -4613,14 +4615,9 @@ int ceph_encode_dentry_release(void **p, struct dentry *dentry,
 	spin_lock(&dentry->d_lock);
 	if (di->lease_session && di->lease_session->s_mds == mds)
 		force = 1;
-	if (!dir) {
-		parent = dget(dentry->d_parent);
-		dir = d_inode(parent);
-	}
 	spin_unlock(&dentry->d_lock);
 
 	ret = ceph_encode_inode_release(p, dir, mds, drop, unless, force);
-	dput(parent);
 
 	spin_lock(&dentry->d_lock);
 	if (ret && di->lease_session && di->lease_session->s_mds == mds) {
-- 
2.43.0