* [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock
@ 2020-01-21 12:31 Jakub Sitnicki
2020-01-22 17:53 ` John Fastabend
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Jakub Sitnicki @ 2020-01-21 12:31 UTC (permalink / raw)
To: netdev; +Cc: John Fastabend, syzbot+d73682fcf7fee6982fe3
As John Fastabend reports [0], psock state tear-down can happen on receive
path *after* unlocking the socket, if the only other psock user, that is
sockmap or sockhash, releases its psock reference before tcp_bpf_recvmsg
does so:
tcp_bpf_recvmsg()
psock = sk_psock_get(sk) <- refcnt 2
lock_sock(sk);
...
sock_map_free() <- refcnt 1
release_sock(sk)
sk_psock_put() <- refcnt 0
Remove the lockdep check for socket lock in psock tear-down that got
introduced in 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during
tear down").
[0] https://lore.kernel.org/netdev/5e25dc995d7d_74082aaee6e465b441@john-XPS-13-9370.notmuch/
Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down")
Reported-by: syzbot+d73682fcf7fee6982fe3@syzkaller.appspotmail.com
Suggested-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---
net/core/skmsg.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/net/core/skmsg.c b/net/core/skmsg.c
index 3866d7e20c07..ded2d5227678 100644
--- a/net/core/skmsg.c
+++ b/net/core/skmsg.c
@@ -594,8 +594,6 @@ EXPORT_SYMBOL_GPL(sk_psock_destroy);
void sk_psock_drop(struct sock *sk, struct sk_psock *psock)
{
- sock_owned_by_me(sk);
-
sk_psock_cork_free(psock);
sk_psock_zap_ingress(psock);
--
2.24.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* RE: [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock
2020-01-21 12:31 [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock Jakub Sitnicki
@ 2020-01-22 17:53 ` John Fastabend
2020-01-22 17:59 ` Daniel Borkmann
2020-01-22 19:30 ` David Miller
2 siblings, 0 replies; 4+ messages in thread
From: John Fastabend @ 2020-01-22 17:53 UTC (permalink / raw)
To: Jakub Sitnicki, netdev; +Cc: John Fastabend, syzbot+d73682fcf7fee6982fe3
Jakub Sitnicki wrote:
> As John Fastabend reports [0], psock state tear-down can happen on receive
> path *after* unlocking the socket, if the only other psock user, that is
> sockmap or sockhash, releases its psock reference before tcp_bpf_recvmsg
> does so:
>
> tcp_bpf_recvmsg()
> psock = sk_psock_get(sk) <- refcnt 2
> lock_sock(sk);
> ...
> sock_map_free() <- refcnt 1
> release_sock(sk)
> sk_psock_put() <- refcnt 0
>
> Remove the lockdep check for socket lock in psock tear-down that got
> introduced in 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during
> tear down").
>
> [0] https://lore.kernel.org/netdev/5e25dc995d7d_74082aaee6e465b441@john-XPS-13-9370.notmuch/
>
> Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down")
> Reported-by: syzbot+d73682fcf7fee6982fe3@syzkaller.appspotmail.com
> Suggested-by: John Fastabend <john.fastabend@gmail.com>
> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
> ---
> net/core/skmsg.c | 2 --
> 1 file changed, 2 deletions(-)
Thanks Jakub, this was not needed I got a bit carried away. I'll add
a selftest to catch this case by duplicating the reproducer into
test_sockmap.c
Acked-by: John Fastabend <john.fastabend@gmail.com>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock
2020-01-21 12:31 [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock Jakub Sitnicki
2020-01-22 17:53 ` John Fastabend
@ 2020-01-22 17:59 ` Daniel Borkmann
2020-01-22 19:30 ` David Miller
2 siblings, 0 replies; 4+ messages in thread
From: Daniel Borkmann @ 2020-01-22 17:59 UTC (permalink / raw)
To: Jakub Sitnicki, netdev; +Cc: John Fastabend, syzbot+d73682fcf7fee6982fe3
On 1/21/20 1:31 PM, Jakub Sitnicki wrote:
> As John Fastabend reports [0], psock state tear-down can happen on receive
> path *after* unlocking the socket, if the only other psock user, that is
> sockmap or sockhash, releases its psock reference before tcp_bpf_recvmsg
> does so:
>
> tcp_bpf_recvmsg()
> psock = sk_psock_get(sk) <- refcnt 2
> lock_sock(sk);
> ...
> sock_map_free() <- refcnt 1
> release_sock(sk)
> sk_psock_put() <- refcnt 0
>
> Remove the lockdep check for socket lock in psock tear-down that got
> introduced in 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during
> tear down").
>
> [0] https://lore.kernel.org/netdev/5e25dc995d7d_74082aaee6e465b441@john-XPS-13-9370.notmuch/
>
> Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down")
> Reported-by: syzbot+d73682fcf7fee6982fe3@syzkaller.appspotmail.com
> Suggested-by: John Fastabend <john.fastabend@gmail.com>
> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Given it's assigned to you right now, David, feel free to take directly to net:
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Thanks,
Daniel
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock
2020-01-21 12:31 [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock Jakub Sitnicki
2020-01-22 17:53 ` John Fastabend
2020-01-22 17:59 ` Daniel Borkmann
@ 2020-01-22 19:30 ` David Miller
2 siblings, 0 replies; 4+ messages in thread
From: David Miller @ 2020-01-22 19:30 UTC (permalink / raw)
To: jakub; +Cc: netdev, john.fastabend, syzbot+d73682fcf7fee6982fe3
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: Tue, 21 Jan 2020 13:31:47 +0100
> As John Fastabend reports [0], psock state tear-down can happen on receive
> path *after* unlocking the socket, if the only other psock user, that is
> sockmap or sockhash, releases its psock reference before tcp_bpf_recvmsg
> does so:
>
> tcp_bpf_recvmsg()
> psock = sk_psock_get(sk) <- refcnt 2
> lock_sock(sk);
> ...
> sock_map_free() <- refcnt 1
> release_sock(sk)
> sk_psock_put() <- refcnt 0
>
> Remove the lockdep check for socket lock in psock tear-down that got
> introduced in 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during
> tear down").
>
> [0] https://lore.kernel.org/netdev/5e25dc995d7d_74082aaee6e465b441@john-XPS-13-9370.notmuch/
>
> Fixes: 7e81a3530206 ("bpf: Sockmap, ensure sock lock held during tear down")
> Reported-by: syzbot+d73682fcf7fee6982fe3@syzkaller.appspotmail.com
> Suggested-by: John Fastabend <john.fastabend@gmail.com>
> Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Applied, thank you.
^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-01-21 12:31 [PATCH net] net, sk_msg: Don't check if sock is locked when tearing down psock Jakub Sitnicki
2020-01-22 17:53 ` John Fastabend
2020-01-22 17:59 ` Daniel Borkmann
2020-01-22 19:30 ` David Miller
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