linux-kernel - Re: [PATCH] nfsd: fix memory leak of async

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Message-ID: <d7bb05ee-c69b-bbed-bfb1-a16ce1ca39f2@canonical.com>
Date:   Tue, 17 Jul 2018 10:33:59 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     "J . Bruce Fields" <bfields@...ldses.org>,
        Jeff Layton <jlayton@...nel.org>, linux-nfs@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nfsd: fix memory leak of async_copy

On 17/07/18 10:30, Dan Carpenter wrote:
> On Mon, Jul 16, 2018 at 01:09:54PM +0100, Colin King wrote:
>> From: Colin Ian King <colin.king@...onical.com>
>>
>> In the case where async_copy is successfully allocated but
>> the call to nfs4_init_cp_state fails, async_copy is not
>> currently freed and the memory is leaked. Fix this by kfree'ing
>> it before returning.
>>
>> Detected by CoverityScan, CID#1471823 ("Resource leak")
>>
>> Fixes: beb1814d5a8a ("NFSD create new stateid for async copy")
>> Signed-off-by: Colin Ian King <colin.king@...onical.com>
>> ---
>>  fs/nfsd/nfs4proc.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
>> index 8f3368353aaf..3fb96a2708b9 100644
>> --- a/fs/nfsd/nfs4proc.c
>> +++ b/fs/nfsd/nfs4proc.c
>> @@ -1295,8 +1295,10 @@ nfsd4_copy(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>>  		async_copy = kzalloc(sizeof(struct nfsd4_copy), GFP_KERNEL);
>>  		if (!async_copy)
>>  			goto out;
>> -		if (!nfs4_init_cp_state(nn, copy))
>> +		if (!nfs4_init_cp_state(nn, copy)) {
>> +			kfree(async_copy);
>>  			goto out;
> 
> It really feels like both this and the kzalloc() failure should be doing
> an of fput() of copy->file_src and copy->file_dst.  The goto out_err
> does an list_del(&copy->copies); but it happens before the
> "list_add(&async_copy->copies ..." so that's likely wrong as well.

Good observation, thanks for spotting that. I suspect I'm a bit out of
my depth figuring out the exact error handling reaping steps here.
Perhaps this is one for the maintainers to figure out a safe cleanup on
these error paths.

> 
> regards,
> dan carpenter
> 
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