linux-kernel - Re: [PATCH][next] afs: fix a dereference on pointer cell before cell is null checked

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Message-ID: <5f9c89a1-148d-1d19-7da7-c362887c92f1@canonical.com>
Date:   Tue, 27 Oct 2020 11:18:44 +0000
From:   Colin Ian King <colin.king@...onical.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-afs@...ts.infradead.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] afs: fix a dereference on pointer cell before cell
 is null checked

On 27/10/2020 11:05, David Howells wrote:
> Colin King <colin.king@...onical.com> wrote:
> 
>> @@ -606,7 +605,7 @@ void afs_unuse_cell(struct afs_net *net, struct afs_cell *cell, enum afs_cell_tr
>>  
>>  	u = atomic_read(&cell->ref);
>>  	a = atomic_dec_return(&cell->active);
>> -	trace_afs_cell(debug_id, u, a, reason);
>> +	trace_afs_cell(cell->debug_id, u, a, reason);
> 
> It's probably better to read cell->debug_id before calling
> atomic_dec_return().
> 
> I have a patch for this based on a report by Dan Carpenter, so no need to send
> a revised patch.

OK - thanks David
> 
> Thanks,
> David
>