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 17AB630FA4 for ; Wed, 20 Sep 2023 12:18:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 92C58C433C7; Wed, 20 Sep 2023 12:18:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1695212322; bh=t8Ase8vNhYOwsuOWvNH2wqkkmJtyGiRyMdE5Fnz5L7g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=LJw165Pw3c3o6f7T0kbWo0/ty4dbQ3OT2KaL8ZBg4kHwLnv5kMRhuULdv5tz2jrH4 vjiq6w8zsDkrJpZrfOjU2DG1Bus4kgSYJkYh0AX5bHM1UCjMxI8DdiwmVXqjhcwyIE aOOeAfVjY7g9gPG/xiC03pRjnBzWJsANeb8v+s+U= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Shigeru Yoshida , "David S. Miller" , Sasha Levin , syzbot+6f98de741f7dbbfc4ccb@syzkaller.appspotmail.com Subject: [PATCH 4.19 232/273] kcm: Fix memory leak in error path of kcm_sendmsg() Date: Wed, 20 Sep 2023 13:31:12 +0200 Message-ID: <20230920112853.546389354@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230920112846.440597133@linuxfoundation.org> References: <20230920112846.440597133@linuxfoundation.org> User-Agent: quilt/0.67 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 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ From: Shigeru Yoshida [ Upstream commit c821a88bd720b0046433173185fd841a100d44ad ] syzbot reported a memory leak like below: BUG: memory leak unreferenced object 0xffff88810b088c00 (size 240): comm "syz-executor186", pid 5012, jiffies 4294943306 (age 13.680s) hex dump (first 32 bytes): 00 89 08 0b 81 88 ff ff 00 00 00 00 00 00 00 00 ................ 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace: [] __alloc_skb+0x1ef/0x230 net/core/skbuff.c:634 [] alloc_skb include/linux/skbuff.h:1289 [inline] [] kcm_sendmsg+0x269/0x1050 net/kcm/kcmsock.c:815 [] sock_sendmsg_nosec net/socket.c:725 [inline] [] sock_sendmsg+0x56/0xb0 net/socket.c:748 [] ____sys_sendmsg+0x365/0x470 net/socket.c:2494 [] ___sys_sendmsg+0xc9/0x130 net/socket.c:2548 [] __sys_sendmsg+0xa6/0x120 net/socket.c:2577 [] do_syscall_x64 arch/x86/entry/common.c:50 [inline] [] do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:80 [] entry_SYSCALL_64_after_hwframe+0x63/0xcd In kcm_sendmsg(), kcm_tx_msg(head)->last_skb is used as a cursor to append newly allocated skbs to 'head'. If some bytes are copied, an error occurred, and jumped to out_error label, 'last_skb' is left unmodified. A later kcm_sendmsg() will use an obsoleted 'last_skb' reference, corrupting the 'head' frag_list and causing the leak. This patch fixes this issue by properly updating the last allocated skb in 'last_skb'. Fixes: ab7ac4eb9832 ("kcm: Kernel Connection Multiplexor module") Reported-and-tested-by: syzbot+6f98de741f7dbbfc4ccb@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=6f98de741f7dbbfc4ccb Signed-off-by: Shigeru Yoshida Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/kcm/kcmsock.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/kcm/kcmsock.c b/net/kcm/kcmsock.c index 55f1bf7a84490..8305e229b4ece 100644 --- a/net/kcm/kcmsock.c +++ b/net/kcm/kcmsock.c @@ -1074,6 +1074,8 @@ static int kcm_sendmsg(struct socket *sock, struct msghdr *msg, size_t len) if (head != kcm->seq_skb) kfree_skb(head); + else if (copied) + kcm_tx_msg(head)->last_skb = skb; err = sk_stream_error(sk, msg->msg_flags, err); -- 2.40.1