linux-kernel - Re: [PATCH] nfsd: Fix a memory leak in an error handling path

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Message-ID: <aa91faa7-eec8-50c7-9e9f-9c9c83d29766@wanadoo.fr>
Date:   Wed, 31 Aug 2022 07:06:00 +0200
From:   Christophe JAILLET <christophe.jaillet@...adoo.fr>
To:     Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Scott Mayhew <smayhew@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-nfs@...r.kernel.org
Subject: Re: [PATCH] nfsd: Fix a memory leak in an error handling path

Le 30/08/2022 à 23:11, Chuck Lever III a écrit :
> 
> 
>> On Aug 26, 2022, at 7:08 AM, Dan Carpenter <dan.carpenter-QHcLZuEGTsvQT0dZR+AlfA@...lic.gmane.org> wrote:
>>
>> On Fri, Aug 26, 2022 at 12:24:54PM +0200, Christophe JAILLET wrote:
>>> If this memdup_user() call fails, the memory allocated in a previous call
>>> a few lines above should be freed. Otherwise it leaks.
>>>
>>> Fixes: 6ee95d1c8991 ("nfsd: add support for upcall version 2")
>>> Signed-off-by: Christophe JAILLET <christophe.jaillet-39ZsbGIQGT5GWvitb5QawA@...lic.gmane.org>
>>> ---
>>> Speculative, untested.
>>> ---
>>> fs/nfsd/nfs4recover.c | 4 +++-
>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
>>> index b29d27eaa8a6..248ff9f4141c 100644
>>> --- a/fs/nfsd/nfs4recover.c
>>> +++ b/fs/nfsd/nfs4recover.c
>>> @@ -815,8 +815,10 @@ __cld_pipe_inprogress_downcall(const struct cld_msg_v2 __user *cmsg,
>>> 				princhash.data = memdup_user(
>>> 						&ci->cc_princhash.cp_data,
>>> 						princhashlen);
>>> -				if (IS_ERR_OR_NULL(princhash.data))
>>> +				if (IS_ERR_OR_NULL(princhash.data)) {
>>> +					kfree(name.data);
>>> 					return -EFAULT;
>>
>> This comment is not directed at you and is not related to your patch.
>> But memdup_user() never returns NULL, only error pointers.  I wrote a
>> fifteen page blog entry about NULL vs error pointers the other week.
>> https://staticthinking.wordpress.com/2022/08/01/mixing-error-pointers-and-null/
>> This should propagate the error code from memdup_user() instead of
>> -EFAULT.
> 
> I take it then that Christophe should redrive this with your suggested
> corrections? I haven't applied this yet because I was waiting for
> follow-up.
> 

Ok, I'll send a small serie of 3 patches...

CJ


> 
> --
> Chuck Lever
> 
> 
> 
>