linux-kernel - [PATCH 5.4 079/203] bpf: skmsg, fix potential psock NULL pointer dereference

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 17 Jan 2020 00:16:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dan Carpenter <dan.carpenter@...cle.com>,
        John Fastabend <john.fastabend@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.4 079/203] bpf: skmsg, fix potential psock NULL pointer dereference

From: John Fastabend <john.fastabend@...il.com>

commit 8163999db445021f2651a8a47b5632483e8722ea upstream.

Report from Dan Carpenter,

 net/core/skmsg.c:792 sk_psock_write_space()
 error: we previously assumed 'psock' could be null (see line 790)

 net/core/skmsg.c
   789 psock = sk_psock(sk);
   790 if (likely(psock && sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED)))
 Check for NULL
   791 schedule_work(&psock->work);
   792 write_space = psock->saved_write_space;
                     ^^^^^^^^^^^^^^^^^^^^^^^^
   793          rcu_read_unlock();
   794          write_space(sk);

Ensure psock dereference on line 792 only occurs if psock is not null.

Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
Fixes: 604326b41a6f ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <john.fastabend@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/core/skmsg.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -793,15 +793,18 @@ static void sk_psock_strp_data_ready(str
 static void sk_psock_write_space(struct sock *sk)
 {
 	struct sk_psock *psock;
-	void (*write_space)(struct sock *sk);
+	void (*write_space)(struct sock *sk) = NULL;
 
 	rcu_read_lock();
 	psock = sk_psock(sk);
-	if (likely(psock && sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED)))
-		schedule_work(&psock->work);
-	write_space = psock->saved_write_space;
+	if (likely(psock)) {
+		if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED))
+			schedule_work(&psock->work);
+		write_space = psock->saved_write_space;
+	}
 	rcu_read_unlock();
-	write_space(sk);
+	if (write_space)
+		write_space(sk);
 }
 
 int sk_psock_init_strp(struct sock *sk, struct sk_psock *psock)