netdev - Re: Fw: [Bug 199429] New: smc_shutdown(net/smc/af_smc.c) has a UAF causing null pointer vulnerability.

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Date:   Wed, 18 Apr 2018 13:46:20 +0200
From:   Ursula Braun <ubraun@...ux.ibm.com>
To:     Stephen Hemminger <stephen@...workplumber.org>,
        Ursula Braun <ubraun@...ux.vnet.ibm.com>
Cc:     netdev@...r.kernel.org
Subject: Re: Fw: [Bug 199429] New: smc_shutdown(net/smc/af_smc.c) has a UAF
 causing null pointer vulnerability.



On 04/18/2018 04:56 AM, Stephen Hemminger wrote:
> This may already be fixed.
> 
> Begin forwarded message:
> 
> Date: Wed, 18 Apr 2018 01:52:59 +0000
> From: bugzilla-daemon@...zilla.kernel.org
> To: stephen@...workplumber.org
> Subject: [Bug 199429] New: smc_shutdown(net/smc/af_smc.c) has a UAF causing null pointer vulnerability.
> 
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=199429
> 
>             Bug ID: 199429
>            Summary: smc_shutdown(net/smc/af_smc.c) has a UAF causing null
>                     pointer vulnerability.
>            Product: Networking
>            Version: 2.5
>     Kernel Version: 4.16.0-rc7
>           Hardware: All
>                 OS: Linux
>               Tree: Mainline
>             Status: NEW
>           Severity: normal
>           Priority: P1
>          Component: Other
>           Assignee: stephen@...workplumber.org
>           Reporter: 1773876454@...com
>         Regression: No
> 
> Created attachment 275431
>   --> https://bugzilla.kernel.org/attachment.cgi?id=275431&action=edit  
> POC
> 
> Syzkaller hit 'general protection fault in kernel_sock_shutdown' bug.
> 
> NET: Registered protocol family 43

Thanks for reporting. This fix is needed here:

 net/smc/af_smc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1314,7 +1314,7 @@ static int smc_shutdown(struct socket *s
 	    (sk->sk_state != SMC_APPCLOSEWAIT2) &&
 	    (sk->sk_state != SMC_APPFINCLOSEWAIT))
 		goto out;
-	if (smc->use_fallback) {
+	if (smc->use_fallback || sk->sk_state == SMC_LISTEN) {
 		rc = kernel_sock_shutdown(smc->clcsock, how);
 		sk->sk_shutdown = smc->clcsock->sk->sk_shutdown;
 		if (sk->sk_shutdown == SHUTDOWN_MASK)

Kind regards, Ursula