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 EE7731C31 for ; Wed, 23 Nov 2022 09:57:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B239C433C1; Wed, 23 Nov 2022 09:57:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1669197464; bh=wt3XbCM6A1KA2PCRzQwfOqepKwTedlpJnOEaesghM9I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=05FpdQKew9FKUkVe8Wa/QyXWunYq1wkN80tNvIo8CRV8s/dRXvnyaypmKVzmm1GW/ 5PSgB3RoCW4Ci7jG6/yvBpLMWrvThLbLRp9JcVz469xa6aECk05KFoL+qb7bTOUyOc lgrUupn3gIeW5urXfM5aljSI+eGk+nwKupSxsiEg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot , Eric Dumazet , Tom Herbert , Jakub Kicinski Subject: [PATCH 6.0 300/314] kcm: avoid potential race in kcm_tx_work Date: Wed, 23 Nov 2022 09:52:25 +0100 Message-Id: <20221123084639.144930835@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221123084625.457073469@linuxfoundation.org> References: <20221123084625.457073469@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Eric Dumazet commit ec7eede369fe5b0d085ac51fdbb95184f87bfc6c upstream. syzbot found that kcm_tx_work() could crash [1] in: /* Primarily for SOCK_SEQPACKET sockets */ if (likely(sk->sk_socket) && test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { <<*>> clear_bit(SOCK_NOSPACE, &sk->sk_socket->flags); sk->sk_write_space(sk); } I think the reason is that another thread might concurrently run in kcm_release() and call sock_orphan(sk) while sk is not locked. kcm_tx_work() find sk->sk_socket being NULL. [1] BUG: KASAN: null-ptr-deref in instrument_atomic_write include/linux/instrumented.h:86 [inline] BUG: KASAN: null-ptr-deref in clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline] BUG: KASAN: null-ptr-deref in kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742 Write of size 8 at addr 0000000000000008 by task kworker/u4:3/53 CPU: 0 PID: 53 Comm: kworker/u4:3 Not tainted 5.19.0-rc3-next-20220621-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: kkcmd kcm_tx_work Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 kasan_report+0xbe/0x1f0 mm/kasan/report.c:495 check_region_inline mm/kasan/generic.c:183 [inline] kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189 instrument_atomic_write include/linux/instrumented.h:86 [inline] clear_bit include/asm-generic/bitops/instrumented-atomic.h:41 [inline] kcm_tx_work+0xff/0x160 net/kcm/kcmsock.c:742 process_one_work+0x996/0x1610 kernel/workqueue.c:2289 worker_thread+0x665/0x1080 kernel/workqueue.c:2436 kthread+0x2e9/0x3a0 kernel/kthread.c:376 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302 Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Reported-by: syzbot Signed-off-by: Eric Dumazet Cc: Tom Herbert Link: https://lore.kernel.org/r/20221012133412.519394-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman --- net/kcm/kcmsock.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1799,10 +1799,10 @@ static int kcm_release(struct socket *so kcm = kcm_sk(sk); mux = kcm->mux; + lock_sock(sk); sock_orphan(sk); kfree_skb(kcm->seq_skb); - lock_sock(sk); /* Purge queue under lock to avoid race condition with tx_work trying * to act when queue is nonempty. If tx_work runs after this point * it will just return.