bpf.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Sasha Levin <sashal@kernel.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: John Fastabend <john.fastabend@gmail.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Sasha Levin <sashal@kernel.org>,
	netdev@vger.kernel.org, bpf@vger.kernel.org
Subject: [PATCH AUTOSEL 5.2 025/123] bpf: sockmap, sock_map_delete needs to use xchg
Date: Tue, 13 Aug 2019 22:09:09 -0400	[thread overview]
Message-ID: <20190814021047.14828-25-sashal@kernel.org> (raw)
In-Reply-To: <20190814021047.14828-1-sashal@kernel.org>

From: John Fastabend <john.fastabend@gmail.com>

[ Upstream commit 45a4521dcbd92e71c9e53031b40e34211d3b4feb ]

__sock_map_delete() may be called from a tcp event such as unhash or
close from the following trace,

  tcp_bpf_close()
    tcp_bpf_remove()
      sk_psock_unlink()
        sock_map_delete_from_link()
          __sock_map_delete()

In this case the sock lock is held but this only protects against
duplicate removals on the TCP side. If the map is free'd then we have
this trace,

  sock_map_free
    xchg()                  <- replaces map entry
    sock_map_unref()
      sk_psock_put()
        sock_map_del_link()

The __sock_map_delete() call however uses a read, test, null over the
map entry which can result in both paths trying to free the map
entry.

To fix use xchg in TCP paths as well so we avoid having two references
to the same map entry.

Fixes: 604326b41a6fb ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/core/sock_map.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index be6092ac69f8a..1d40e040320d2 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -281,16 +281,20 @@ static int __sock_map_delete(struct bpf_stab *stab, struct sock *sk_test,
 			     struct sock **psk)
 {
 	struct sock *sk;
+	int err = 0;
 
 	raw_spin_lock_bh(&stab->lock);
 	sk = *psk;
 	if (!sk_test || sk_test == sk)
-		*psk = NULL;
+		sk = xchg(psk, NULL);
+
+	if (likely(sk))
+		sock_map_unref(sk, psk);
+	else
+		err = -EINVAL;
+
 	raw_spin_unlock_bh(&stab->lock);
-	if (unlikely(!sk))
-		return -EINVAL;
-	sock_map_unref(sk, psk);
-	return 0;
+	return err;
 }
 
 static void sock_map_delete_from_link(struct bpf_map *map, struct sock *sk,
-- 
2.20.1


  parent reply	other threads:[~2019-08-14  2:39 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20190814021047.14828-1-sashal@kernel.org>
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 020/123] libbpf: sanitize VAR to conservative 1-byte INT Sasha Levin
2019-08-14  2:09 ` Sasha Levin [this message]
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 026/123] bpf: sockmap, synchronize_rcu before free'ing map Sasha Levin
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 027/123] bpf: sockmap, only create entry if ulp is not already enabled Sasha Levin
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 028/123] selftests/bpf: fix sendmsg6_prog on s390 Sasha Levin
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 034/123] bpf: fix access to skb_shared_info->gso_segs Sasha Levin
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 035/123] selftests/bpf: add another gso_segs access Sasha Levin
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 036/123] libbpf: fix using uninitialized ioctl results Sasha Levin
2019-08-14  2:09 ` [PATCH AUTOSEL 5.2 042/123] libbpf: silence GCC8 warning about string truncation Sasha Levin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20190814021047.14828-25-sashal@kernel.org \
    --to=sashal@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=daniel@iogearbox.net \
    --cc=john.fastabend@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=stable@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).