From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B5A3D1C3BE9; Wed, 19 Feb 2025 08:45:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739954723; cv=none; b=GFE+Cx8QYCJ4KMkxcAosPCuhDP6XH/3oUijQy9DF7pPwC4UIQ6EWAECXNNDW9UdywIhJmEWYRpZAU14hL8yWpGl27Tu66rpz0H9lKHpPhpit1L895NSAVY0hEYt8Uj0HgIerkyoD5nimWB8nV8PNun78NXzPnbAf7eHZHFbdH/Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739954723; c=relaxed/simple; bh=cFfdDMNsic07pMgzqznwFRfFP5mG5lSwdrbuF8kZbKI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=W6883Vd9DAeDZyZ9NM9elj5BWERjFUiQtTNNeiN7YgaI9HxqzYOGrHilscldrvs29zGWOLOcj4RnNZOk70m15qqcLvNkUkQSMfNV/d2o6bfeAOXj8rPH0vZAzKZe0IObeSfF7U2gef8c+MgaV3xLNT/g7NcQ/4mzFZFBy5XBtZY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=vyBLXk6e; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="vyBLXk6e" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0398FC4CED1; Wed, 19 Feb 2025 08:45:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1739954723; bh=cFfdDMNsic07pMgzqznwFRfFP5mG5lSwdrbuF8kZbKI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=vyBLXk6ew65uR1ULpisqYK0kh+tB3IubkHVfc3eD3BRj88clE6SJXoHqmjMQhJN3R cXnifaRf63lykPrL1uYQOvND9QpP+KeI9T8U+aGm2Srus65blRCn6gTYD9hJKFPCt6 DSnCh//GUWAZtCf4HF9NIbC66btC54FnW56KzoxQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+33841dc6aa3e1d86b78a@syzkaller.appspotmail.com, Murad Masimov , Jakub Kicinski , Sasha Levin Subject: [PATCH 6.12 016/230] ax25: Fix refcount leak caused by setting SO_BINDTODEVICE sockopt Date: Wed, 19 Feb 2025 09:25:33 +0100 Message-ID: <20250219082602.336964247@linuxfoundation.org> X-Mailer: git-send-email 2.48.1 In-Reply-To: <20250219082601.683263930@linuxfoundation.org> References: <20250219082601.683263930@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Murad Masimov [ Upstream commit bca0902e61731a75fc4860c8720168d9f1bae3b6 ] If an AX25 device is bound to a socket by setting the SO_BINDTODEVICE socket option, a refcount leak will occur in ax25_release(). Commit 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()") added decrement of device refcounts in ax25_release(). In order for that to work correctly the refcounts must already be incremented when the device is bound to the socket. An AX25 device can be bound to a socket by either calling ax25_bind() or setting SO_BINDTODEVICE socket option. In both cases the refcounts should be incremented, but in fact it is done only in ax25_bind(). This bug leads to the following issue reported by Syzkaller: ================================================================ refcount_t: decrement hit 0; leaking memory. WARNING: CPU: 1 PID: 5932 at lib/refcount.c:31 refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Modules linked in: CPU: 1 UID: 0 PID: 5932 Comm: syz-executor424 Not tainted 6.13.0-rc4-syzkaller-00110-g4099a71718b0 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x1ed/0x210 lib/refcount.c:31 Call Trace: __refcount_dec include/linux/refcount.h:336 [inline] refcount_dec include/linux/refcount.h:351 [inline] ref_tracker_free+0x710/0x820 lib/ref_tracker.c:236 netdev_tracker_free include/linux/netdevice.h:4156 [inline] netdev_put include/linux/netdevice.h:4173 [inline] netdev_put include/linux/netdevice.h:4169 [inline] ax25_release+0x33f/0xa10 net/ax25/af_ax25.c:1069 __sock_release+0xb0/0x270 net/socket.c:640 sock_close+0x1c/0x30 net/socket.c:1408 ... do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f ... ================================================================ Fix the implementation of ax25_setsockopt() by adding increment of refcounts for the new device bound, and decrement of refcounts for the old unbound device. Fixes: 9fd75b66b8f6 ("ax25: Fix refcount leaks caused by ax25_cb_del()") Reported-by: syzbot+33841dc6aa3e1d86b78a@syzkaller.appspotmail.com Signed-off-by: Murad Masimov Link: https://patch.msgid.link/20250203091203.1744-1-m.masimov@mt-integration.ru Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/ax25/af_ax25.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index aa6c714892ec9..9f3b8b682adb2 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -685,6 +685,15 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname, break; } + if (ax25->ax25_dev) { + if (dev == ax25->ax25_dev->dev) { + rcu_read_unlock(); + break; + } + netdev_put(ax25->ax25_dev->dev, &ax25->dev_tracker); + ax25_dev_put(ax25->ax25_dev); + } + ax25->ax25_dev = ax25_dev_ax25dev(dev); if (!ax25->ax25_dev) { rcu_read_unlock(); @@ -692,6 +701,8 @@ static int ax25_setsockopt(struct socket *sock, int level, int optname, break; } ax25_fillin_cb(ax25, ax25->ax25_dev); + netdev_hold(dev, &ax25->dev_tracker, GFP_ATOMIC); + ax25_dev_hold(ax25->ax25_dev); rcu_read_unlock(); break; -- 2.39.5