linux-kernel - Re: Oops (request_key_auth_describe) while running cve-2016-7042 from LTP

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Date:   Fri, 30 Aug 2019 16:02:03 +0530
From:   Sachin Sant <sachinp@...ux.vnet.ibm.com>
To:     Hillf Danton <hdanton@...a.com>
Cc:     dhowells@...hat.com, linuxppc-dev@...abs.org,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: Oops (request_key_auth_describe) while running cve-2016-7042 from
 LTP



> On 30-Aug-2019, at 2:26 PM, Hillf Danton <hdanton@...a.com> wrote:
> 
> 
> On Fri, 30 Aug 2019 12:18:07 +0530 Sachin Sant wrote:
>> 
>> [ 8074.351033] BUG: Kernel NULL pointer dereference at 0x00000038
>> [ 8074.351046] Faulting instruction address: 0xc0000000004ddf30
>> [ 8074.351052] Oops: Kernel access of bad area, sig: 11 [#1]
>> [ 8074.351056] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
> 
> Add rcu gp.
> 
> --- a/security/keys/request_key_auth.c
> +++ b/security/keys/request_key_auth.c
> @@ -64,12 +64,19 @@ static int request_key_auth_instantiate(
> static void request_key_auth_describe(const struct key *key,
> 				      struct seq_file *m)
> {
> -	struct request_key_auth *rka = dereference_key_rcu(key);
> +	struct request_key_auth *rka;
> +
> +	rcu_read_lock();
> +	rka = dereference_key_rcu(key);
> +	if (!rka)
> +		goto out;
> 

Thanks for the patch. Works for me. Test ran fine without any problems.

Tested-by: Sachin Sant <sachinp@...ux.vnet.ibm.com>

Thanks
-Sachin