linux-kernel - [PATCH v1] fs:dlm:Fix potential null pointer dereference on pointer

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Date:   Fri, 16 Jun 2023 10:48:24 +0800
From:   Wang Ming <machel@...o.com>
To:     Christine Caulfield <ccaulfie@...hat.com>,
        David Teigland <teigland@...hat.com>, cluster-devel@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com, gregkh@...uxfoundation.org,
        Wang Ming <machel@...o.com>
Subject: [PATCH v1] fs:dlm:Fix potential null pointer dereference on pointer

Before dereferencing the pointer, first judge whether
it is NULL, if it is NULL, there is no need to dereference.
Fix the following coccicheck ERROR:

fs/dlm/lowcomms.c:1082:26-28: ERROR: newcon -> sock is NULL
but dereferenced.

Signed-off-by: Wang Ming <machel@...o.com>
---
 fs/dlm/lowcomms.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 3d3802c47..0a2d1b5ab 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -1079,7 +1079,18 @@ static int accept_from_sock(void)
        sock_set_mark(newsock->sk, mark);

        down_write(&newcon->sock_lock);
-       if (newcon->sock) {
+       if (newcon->sock == NULL) {
+               /*  accept copies the sk after we've saved the callbacks, so we
+                *  don't want to save them a second time or comm errors will
+                *  result in calling sk_error_report recursively.
+                */
+               add_sock(newsock, newcon);
+
+               /* check if we receved something while adding */
+               lock_sock(newcon->sock->sk);
+               lowcomms_queue_rwork(newcon);
+               release_sock(newcon->sock->sk);
+       } else {
                struct connection *othercon = newcon->othercon;

                if (!othercon) {
@@ -1110,17 +1121,7 @@ static int accept_from_sock(void)
                release_sock(othercon->sock->sk);
                up_write(&othercon->sock_lock);
        }
-       else {
-               /* accept copies the sk after we've saved the callbacks, so we
-                  don't want to save them a second time or comm errors will
-                  result in calling sk_error_report recursively. */
-               add_sock(newsock, newcon);

-               /* check if we receved something while adding */
-               lock_sock(newcon->sock->sk);
-               lowcomms_queue_rwork(newcon);
-               release_sock(newcon->sock->sk);
-       }
        up_write(&newcon->sock_lock);
        srcu_read_unlock(&connections_srcu, idx);

--
2.25.1

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