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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Xiubo Li <xiubli@redhat.com>,
        Jeff Layton <jlayton@kernel.org>,
        Aaron Tomlin <atomlin@redhat.com>,
        Ilya Dryomov <idryomov@gmail.com>
Subject: [PATCH 5.15 034/177] ceph: fix possible NULL pointer dereference for req->r_session
Date:   Wed,  4 May 2022 18:43:47 +0200
Message-Id: <20220504153056.012271165@linuxfoundation.org>
In-Reply-To: <20220504153053.873100034@linuxfoundation.org>
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From: Xiubo Li <xiubli@redhat.com>

commit 7acae6183cf37c48b8da48bbbdb78820fb3913f3 upstream.

The request will be inserted into the ci->i_unsafe_dirops before
assigning the req->r_session, so it's possible that we will hit
NULL pointer dereference bug here.

Cc: stable@vger.kernel.org
URL: https://tracker.ceph.com/issues/55327
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Tested-by: Aaron Tomlin <atomlin@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/ceph/caps.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2266,6 +2266,8 @@ retry:
 			list_for_each_entry(req, &ci->i_unsafe_dirops,
 					    r_unsafe_dir_item) {
 				s = req->r_session;
+				if (!s)
+					continue;
 				if (unlikely(s->s_mds >= max_sessions)) {
 					spin_unlock(&ci->i_unsafe_lock);
 					for (i = 0; i < max_sessions; i++) {
@@ -2286,6 +2288,8 @@ retry:
 			list_for_each_entry(req, &ci->i_unsafe_iops,
 					    r_unsafe_target_item) {
 				s = req->r_session;
+				if (!s)
+					continue;
 				if (unlikely(s->s_mds >= max_sessions)) {
 					spin_unlock(&ci->i_unsafe_lock);
 					for (i = 0; i < max_sessions; i++) {