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 C6A5D3568F8; Tue, 26 Aug 2025 14:12:04 +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=1756217524; cv=none; b=ai+71gxmizRH3bL2+xWZlAyePVgu/rVcnGFmW2owFbrp8aQ/dOcsgIfUtqaTYtWTA+CW4/DdtNMtTU0K8/8yft1azuZf2n6c7YxTEjNaC1v6+yeQ3f7rBIWCrjDal9dd0qQPnM4j+i0BK8ukVU5IosaIIqZvf6quk+QYxu63Tug= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756217524; c=relaxed/simple; bh=k9KDNcDVmyEUUe/3ZinkO6u9leQxos2+50D0nLP32FQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Tqy0ffFIsDfJFJX3ff7NZBDMHQv4w6SHvmbU0d2vbbgcKQUwCg8X3vP4QA6a4lvok7TfgynXXlho9Bp7mAreWwtGEGOFYJEGmVZZonoQ+HDr3CQkRUUi2OEZEKcpB9Lwva8uEU9PjeBlMHzIJ2W3zTgZmlDvIt6oIUVpSm9LPPI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=axUP+D0M; 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="axUP+D0M" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 50229C4CEF1; Tue, 26 Aug 2025 14:12:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1756217524; bh=k9KDNcDVmyEUUe/3ZinkO6u9leQxos2+50D0nLP32FQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=axUP+D0MQLTmhL+t3/2fmPtes9ie44ma31ajB3rs3yfsc7GLrY7MNhxiPQ9KHpIyL lSrVtNIKKnDC6YEBEvrIjgwV50sJ3oOd/bQdOmeOQicwsIpdIjFVO96NXuIsYvC5bN UwR7mqOxdRz72JzPn+Ltn6Rix62pTIqda9Mc8mNA= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+afad90ffc8645324afe5@syzkaller.appspotmail.com, Eric Dumazet , Dawid Osuchowski , Jakub Kicinski , Sasha Levin Subject: [PATCH 5.10 176/523] pptp: ensure minimal skb length in pptp_xmit() Date: Tue, 26 Aug 2025 13:06:26 +0200 Message-ID: <20250826110928.800394014@linuxfoundation.org> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250826110924.562212281@linuxfoundation.org> References: <20250826110924.562212281@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 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Dumazet [ Upstream commit de9c4861fb42f0cd72da844c3c34f692d5895b7b ] Commit aabc6596ffb3 ("net: ppp: Add bound checking for skb data on ppp_sync_txmung") fixed ppp_sync_txmunge() We need a similar fix in pptp_xmit(), otherwise we might read uninit data as reported by syzbot. BUG: KMSAN: uninit-value in pptp_xmit+0xc34/0x2720 drivers/net/ppp/pptp.c:193 pptp_xmit+0xc34/0x2720 drivers/net/ppp/pptp.c:193 ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2290 [inline] ppp_input+0x1d6/0xe60 drivers/net/ppp/ppp_generic.c:2314 pppoe_rcv_core+0x1e8/0x760 drivers/net/ppp/pppoe.c:379 sk_backlog_rcv+0x142/0x420 include/net/sock.h:1148 __release_sock+0x1d3/0x330 net/core/sock.c:3213 release_sock+0x6b/0x270 net/core/sock.c:3767 pppoe_sendmsg+0x15d/0xcb0 drivers/net/ppp/pppoe.c:904 sock_sendmsg_nosec net/socket.c:712 [inline] __sock_sendmsg+0x330/0x3d0 net/socket.c:727 ____sys_sendmsg+0x893/0xd80 net/socket.c:2566 ___sys_sendmsg+0x271/0x3b0 net/socket.c:2620 __sys_sendmmsg+0x2d9/0x7c0 net/socket.c:2709 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+afad90ffc8645324afe5@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/68887d86.a00a0220.b12ec.00cd.GAE@google.com/T/#u Signed-off-by: Eric Dumazet Reviewed-by: Dawid Osuchowski Link: https://patch.msgid.link/20250729080207.1863408-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- drivers/net/ppp/pptp.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/drivers/net/ppp/pptp.c b/drivers/net/ppp/pptp.c index 05a75b5a8b68..1b306562f916 100644 --- a/drivers/net/ppp/pptp.c +++ b/drivers/net/ppp/pptp.c @@ -159,9 +159,7 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) int len; unsigned char *data; __u32 seq_recv; - - - struct rtable *rt; + struct rtable *rt = NULL; struct net_device *tdev; struct iphdr *iph; int max_headroom; @@ -179,16 +177,20 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) { struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom); - if (!new_skb) { - ip_rt_put(rt); + + if (!new_skb) goto tx_error; - } + if (skb->sk) skb_set_owner_w(new_skb, skb->sk); consume_skb(skb); skb = new_skb; } + /* Ensure we can safely access protocol field and LCP code */ + if (!pskb_may_pull(skb, 3)) + goto tx_error; + data = skb->data; islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7; @@ -262,6 +264,7 @@ static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb) return 1; tx_error: + ip_rt_put(rt); kfree_skb(skb); return 1; } -- 2.39.5