Re: [PATCH] sock: fix /proc/net/sockstat underflow in sk_clone_lock()
From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Date: 2021-11-14 22:48:45
On 2021/11/15 5:01, Eric Dumazet wrote:
On 11/13/21 10:02 PM, Tetsuo Handa wrote:quoted
sk_clone_lock() needs to call get_net() and sock_inuse_inc() together, or
s/sock_inuse_inc/sock_inuse_add/
quoted
socket_seq_show() will underflow when __sk_free() from sk_free() from sk_free_unlock_clone() is called.IMO, a "sock_inuse_get() underflow" is a very different problem,
Yes, a different problem. I found this problem while trying to examine https://syzkaller.appspot.com/bug?extid=694120e1002c117747ed where somebody might be failing to call get_net() or we might be failing to make sure that all timers are synchronously stopped before put_net().
I suspect this should be fixed with the following patch.
My patch addresses a permanent underflow problem which remains as long as that namespace exists. Your patch addresses a temporal underflow problem which happens due to calculating the sum without locks. Therefore, we can apply both patches if we want.
quoted hunk ↗ jump to hunk
diff --git a/net/core/sock.c b/net/core/sock.c index c57d9883f62c75f522b7f6bc68451aaf8429dc83..bac8e2b62521301ce897728fff9622c4c05419a3 100644 --- a/net/core/sock.c +++ b/net/core/sock.c@@ -3573,7 +3573,7 @@ int sock_inuse_get(struct net *net) for_each_possible_cpu(cpu) res += *per_cpu_ptr(net->core.sock_inuse, cpu); - return res; + return max(res, 0); } EXPORT_SYMBOL_GPL(sock_inuse_get);Bug added in commit 648845ab7e200993dccd3948c719c858368c91e7 Author: Tonghao Zhang [off-list ref] Date: Thu Dec 14 05:51:58 2017 -0800 sock: Move the socket inuse to namespace.