netdev - [PATCH net-next] bpf: restore skb->sk before pskb

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:   Wed, 26 Apr 2017 09:09:23 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Andrey Konovalov <andreyknvl@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net-next] bpf: restore skb->sk before pskb_trim() call

From: Eric Dumazet <edumazet@...gle.com>

While testing a fix [1] in ___pskb_trim(), addressing the WARN_ON_ONCE()
in skb_try_coalesce() reported by Andrey, I found that we had an skb
with skb->sk set but no skb->destructor.

This invalidated heuristic found in commit 158f323b9868 ("net: adjust
skb->truesize in pskb_expand_head()") and in cited patch.

Considering the BUG_ON(skb->sk) we have in skb_orphan(), we should
restrain the temporary setting to a minimal section.

[1] https://patchwork.ozlabs.org/patch/755570/ 
    net: adjust skb->truesize in ___pskb_trim()

Fixes: 8f917bba0042 ("bpf: pass sk to helper functions")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Willem de Bruijn <willemb@...gle.com>
Cc: Andrey Konovalov <andreyknvl@...gle.com>
---
 net/core/filter.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index 9a37860a80fc78378705b681ec3b0468824cbcf4..a253a6197e6b37a7ae2fe451c646b01c861a3e22 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -98,8 +98,8 @@ int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)
 
 		skb->sk = sk;
 		pkt_len = bpf_prog_run_save_cb(filter->prog, skb);
-		err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
 		skb->sk = save_sk;
+		err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;
 	}
 	rcu_read_unlock();