On Mon, 2025-08-04 at 22:47 +0000, Eric Biggers wrote:
> Since MD5 digests are fixed-size, make nfs4_make_rec_clidname() store
> the digest in a stack buffer instead of a dynamically allocated buffer.
> Use MD5_DIGEST_SIZE instead of a hard-coded value, both in
> nfs4_make_rec_clidname() and in the definition of HEXDIR_LEN.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> fs/nfsd/nfs4recover.c | 15 ++++-----------
> fs/nfsd/state.h | 4 +++-
> 2 files changed, 7 insertions(+), 12 deletions(-)
>
> diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
> index 54f5e5392ef9..e2b9472e5c78 100644
> --- a/fs/nfsd/nfs4recover.c
> +++ b/fs/nfsd/nfs4recover.c
> @@ -93,11 +93,11 @@ nfs4_reset_creds(const struct cred *original)
> }
>
> static int
> nfs4_make_rec_clidname(char dname[HEXDIR_LEN], const struct xdr_netobj *clname)
> {
> - struct xdr_netobj cksum;
> + u8 digest[MD5_DIGEST_SIZE];
> struct crypto_shash *tfm;
> int status;
>
> dprintk("NFSD: nfs4_make_rec_clidname for %.*s\n",
> clname->len, clname->data);
> @@ -105,27 +105,20 @@ nfs4_make_rec_clidname(char dname[HEXDIR_LEN], const struct xdr_netobj *clname)
> if (IS_ERR(tfm)) {
> status = PTR_ERR(tfm);
> goto out_no_tfm;
> }
>
> - cksum.len = crypto_shash_digestsize(tfm);
> - cksum.data = kmalloc(cksum.len, GFP_KERNEL);
> - if (cksum.data == NULL) {
> - status = -ENOMEM;
> - goto out;
> - }
> -
> status = crypto_shash_tfm_digest(tfm, clname->data, clname->len,
> - cksum.data);
> + digest);
> if (status)
> goto out;
>
> - sprintf(dname, "%*phN", 16, cksum.data);
> + static_assert(HEXDIR_LEN == 2 * MD5_DIGEST_SIZE + 1);
> + sprintf(dname, "%*phN", MD5_DIGEST_SIZE, digest);
>
> status = 0;
> out:
> - kfree(cksum.data);
> crypto_free_shash(tfm);
> out_no_tfm:
> return status;
> }
>
> diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h
> index 8adc2550129e..b7d4c6d6f3d4 100644
> --- a/fs/nfsd/state.h
> +++ b/fs/nfsd/state.h
> @@ -33,10 +33,11 @@
> */
>
> #ifndef _NFSD4_STATE_H
> #define _NFSD4_STATE_H
>
> +#include <crypto/md5.h>
> #include <linux/idr.h>
> #include <linux/refcount.h>
> #include <linux/sunrpc/svc_xprt.h>
> #include "nfsfh.h"
> #include "nfsd.h"
> @@ -379,11 +380,12 @@ struct nfsd4_sessionid {
> clientid_t clientid;
> u32 sequence;
> u32 reserved;
> };
>
> -#define HEXDIR_LEN 33 /* hex version of 16 byte md5 of cl_name plus '\0' */
> +/* Length of MD5 digest as hex, plus terminating '\0' */
> +#define HEXDIR_LEN (2 * MD5_DIGEST_SIZE + 1)
>
> /*
> * State Meaning Where set
> * --------------------------------------------------------------------------
> * | NFSD4_ACTIVE | Confirmed, active | Default |
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
