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

[Christophe JAILLET]

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@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxx>
> > > ---
> > > 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