linux-kernel - Re: [PATCH v4 3/3] btrfs: Use kfree() in btrfs_ioctl_get_subvol

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Date:   Tue, 16 Jun 2020 11:05:22 -0400
From:   Waiman Long <longman@...hat.com>
To:     dsterba@...e.cz, Andrew Morton <akpm@...ux-foundation.org>,
        David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Joe Perches <joe@...ches.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Rientjes <rientjes@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>, linux-mm@...ck.org,
        keyrings@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-amlogic@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
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        linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, linux-cifs@...r.kernel.org,
        linux-fscrypt@...r.kernel.org, ecryptfs@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-bluetooth@...r.kernel.org,
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        linux-integrity@...r.kernel.org
Subject: Re: [PATCH v4 3/3] btrfs: Use kfree() in
 btrfs_ioctl_get_subvol_info()

On 6/16/20 10:48 AM, David Sterba wrote:
> On Mon, Jun 15, 2020 at 09:57:18PM -0400, Waiman Long wrote:
>> In btrfs_ioctl_get_subvol_info(), there is a classic case where kzalloc()
>> was incorrectly paired with kzfree(). According to David Sterba, there
>> isn't any sensitive information in the subvol_info that needs to be
>> cleared before freeing. So kfree_sensitive() isn't really needed,
>> use kfree() instead.
>>
>> Reported-by: David Sterba <dsterba@...e.cz>
>> Signed-off-by: Waiman Long <longman@...hat.com>
>> ---
>>   fs/btrfs/ioctl.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index f1dd9e4271e9..e8f7c5f00894 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -2692,7 +2692,7 @@ static int btrfs_ioctl_get_subvol_info(struct file *file, void __user *argp)
>>   	btrfs_put_root(root);
>>   out_free:
>>   	btrfs_free_path(path);
>> -	kfree_sensitive(subvol_info);
>> +	kfree(subvol_info);
> I would rather merge a patch doing to kzfree -> kfree instead of doing
> the middle step to switch it to kfree_sensitive. If it would help
> integration of your patchset I can push it to the next rc so there are
> no kzfree left in the btrfs code. Treewide change like that can take
> time so it would be one less problem to care about for you.
>
Sure, I will move it forward in the patch series.

Thanks,
Longman