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

[Dan Carpenter <dan.carpenter@oracle.com>]

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@wanadoo.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.

regards,
dan carpenter