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

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Date:   Wed, 31 Aug 2022 08:44:07 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Chuck Lever III <chuck.lever@...cle.com>
Cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Jeff Layton <jlayton@...nel.org>,
        Bruce Fields <bfields@...hat.com>,
        Scott Mayhew <smayhew@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>
Subject: Re: [PATCH] nfsd: Fix a memory leak in an error handling path

On Tue, Aug 30, 2022 at 09:11:54PM +0000, Chuck Lever III wrote:
> 
> 
> > On Aug 26, 2022, at 7:08 AM, Dan Carpenter <dan.carpenter@...cle.com> 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@...adoo.fr>
> >> ---
> >> 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.

No, that's a different thing.  If anyone wants to clean that up then it
should be part of a different patch.

regards,
dan carpenter