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net: rds: acquire refcount on TCP sockets

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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@syzkaller.appspotmail.com>
Fixes: 26abe14379 ("net: Modify sk_alloc to not reference count the netns of kernel sockets.")
Fixes: 8a68173691 ("net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket")
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Tested-by: syzbot <syzbot+694120e1002c117747ed@syzkaller.appspotmail.com>
Link: https://lore.kernel.org/r/a5fb1fc4-2284-3359-f6a0-e4e390239d7b@I-love.SAKURA.ne.jp
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Tetsuo Handa 2022-05-02 10:40:18 +09:00 committed by Paolo Abeni
parent f5c2174a37
commit 3a58f13a88
1 changed files with 8 additions and 0 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

8
net/rds/tcp.c
View file

@ -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;