linux-kernel - Re: [PATCH v3] net: xfrm: Add '_rcu' tag for rcu protected pointer in netns

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Date:   Mon, 18 Mar 2019 10:22:46 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Su Yanjun <suyj.fnst@...fujitsu.com>
Cc:     davem@...emloft.net, fw@...len.de, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] net: xfrm: Add '_rcu' tag for rcu protected pointer in
 netns_xfrm



On 03/11/2019 03:10 AM, Steffen Klassert wrote:
> On Wed, Mar 06, 2019 at 08:54:08PM -0500, Su Yanjun wrote:
>> For rcu protected pointers, we'd better add '__rcu' for them.
>>
>> Once added '__rcu' tag for rcu protected pointer, the sparse tool reports
>> warnings.
>>
>> net/xfrm/xfrm_user.c:1198:39: sparse:    expected struct sock *sk
>> net/xfrm/xfrm_user.c:1198:39: sparse:    got struct sock [noderef] <asn:4> *nlsk
>> [...]
>>
>> So introduce a new wrapper function of nlmsg_unicast  to handle type
>> conversions.
>>
>> This patch also fixes a direct access of a rcu protected socket.
>>
>> Fixes: be33690d8fcf("[XFRM]: Fix aevent related crash")
>> Signed-off-by: Su Yanjun <suyj.fnst@...fujitsu.com>
> 
> Patch applied, thanks!
> 

Has this patch ever been tested ?

I do not see the needed rcu_read_lock() / rcu_read_unlock() that are mandated for
rcu_dereference() correctness.

All changes like that should be tested with :

CONFIG_LOCKDEP=y
CONFIG_PROVE_RCU=y