netdev - Re: [Patch net] rds: mark bound socket with SOCK_RCU

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20180910223412.GI4668@oracle.com>
Date:   Mon, 10 Sep 2018 18:34:12 -0400
From:   Sowmini Varadhan <sowmini.varadhan@...cle.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     netdev@...r.kernel.org,
        Santosh Shilimkar <santosh.shilimkar@...cle.com>,
        rds-devel@....oracle.com
Subject: Re: [Patch net] rds: mark bound socket with SOCK_RCU_FREE

On (09/10/18 15:24), Cong Wang wrote:
> 
> When a rds sock is bound, it is inserted into the bind_hash_table
> which is protected by RCU. But when releasing rd sock, after it
> is removed from this hash table, it is freed immediately without
> respecting RCU grace period. This could cause some use-after-free
> as reported by syzbot.
> 

I have no objection to the change itself, but the syzbot failures
are caused for a very simple reason: we need synchronize_net()
in rds_release before we remove the rds_sock from the bind_hash_table.

I already pointed this out in 
  https://www.spinics.net/lists/netdev/msg475074.html

I think the objection to synchronize_net() is that it can cause
perf issues (I'm told that rds_release() has been known to be held
up by other threads in rcu critical sections?) but I personally
dont see any other alternative to this (other than going back
to rwlock, instead of rcu)

--Sowmini