netdev - [PATCH] tcp: detect use sendpage for slab-based objects

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-next>] [day] [month] [year] [list]

Date:   Thu, 21 Feb 2019 18:30:17 +0300
From:   Vasily Averin <vvs@...tuozzo.com>
To:     Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org
Subject: [PATCH] tcp: detect use sendpage for slab-based objects

There was few incidents when XFS over network block device generates
IO requests with slab-based metadata. If these requests are processed
via sendpage path tcp_sendpage() calls skb_can_coalesce() and merges
neighbour slab objects into one skb fragment.

If receiving side is located on the same host tcp_recvmsg() can trigger
following BUG_ON
usercopy: kernel memory exposure attempt detected
		from XXXXXX (kmalloc-512) (1024 bytes)

This patch helps to detect the reason of similar incidents on sending side.

Signed-off-by: Vasily Averin <vvs@...tuozzo.com>
---
 net/ipv4/tcp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 2079145a3b7c..cf9572f4fc0f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -996,6 +996,7 @@ ssize_t do_tcp_sendpages(struct sock *sk, struct page *page, int offset,
 			goto wait_for_memory;
 
 		if (can_coalesce) {
+			WARN_ON_ONCE(PageSlab(page));
 			skb_frag_size_add(&skb_shinfo(skb)->frags[i - 1], copy);
 		} else {
 			get_page(page);
-- 
2.17.1