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

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Date:   Tue, 17 Jul 2018 06:13:20 -0400
From:   "J . Bruce Fields" <bfields@...ldses.org>
To:     Colin Ian King <colin.king@...onical.com>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        Jeff Layton <jlayton@...nel.org>, linux-nfs@...r.kernel.org,
        kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org,
        Olga Kornievskaia <aglo@...ch.edu>
Subject: Re: [PATCH] nfsd: fix memory leak of async_copy

Cc'ing Olga.--b.

On Tue, Jul 17, 2018 at 10:33:59AM +0100, Colin Ian King wrote:
> 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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> >