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Message-ID: <a5fb1fc4-2284-3359-f6a0-e4e390239d7b@I-love.SAKURA.ne.jp>
Date: Mon, 2 May 2022 10:40:18 +0900
From: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Santosh Shilimkar <santosh.shilimkar@...cle.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
syzbot <syzbot+694120e1002c117747ed@...kaller.appspotmail.com>,
netdev <netdev@...r.kernel.org>,
syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
OFED mailing list <linux-rdma@...r.kernel.org>
Subject: [PATCH v2] net: rds: acquire refcount on TCP sockets
syzbot is reporting use-after-free read in tcp_retransmit_timer() [1],
for TCP socket used by RDS is accessing sock_net() without acquiring a
refcount on net namespace. Since TCP's retransmission can happen after
a process which created net namespace terminated, we need to explicitly
acquire a refcount.
Link: https://syzkaller.appspot.com/bug?extid=694120e1002c117747ed [1]
Reported-by: syzbot <syzbot+694120e1002c117747ed@...kaller.appspotmail.com>
Fixes: 26abe14379f8e2fa ("net: Modify sk_alloc to not reference count the netns of kernel sockets.")
Fixes: 8a68173691f03661 ("net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket")
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+694120e1002c117747ed@...kaller.appspotmail.com>
---
Changes in v2:
Add Fixes: tag.
Move to inside lock_sock() section.
I chose 26abe14379f8e2fa and 8a68173691f03661 which went to 4.2 for Fixes: tag,
for refcount was implicitly taken when 70041088e3b97662 ("RDS: Add TCP transport
to RDS") was added to 2.6.32.
net/rds/tcp.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 5327d130c4b5..2f638f8b7b1e 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -495,6 +495,14 @@ void rds_tcp_tune(struct socket *sock)
tcp_sock_set_nodelay(sock->sk);
lock_sock(sk);
+ /* TCP timer functions might access net namespace even after
+ * a process which created this net namespace terminated.
+ */
+ if (!sk->sk_net_refcnt) {
+ sk->sk_net_refcnt = 1;
+ get_net_track(net, &sk->ns_tracker, GFP_KERNEL);
+ sock_inuse_add(net, 1);
+ }
if (rtn->sndbuf_size > 0) {
sk->sk_sndbuf = rtn->sndbuf_size;
sk->sk_userlocks |= SOCK_SNDBUF_LOCK;
--
2.34.1
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