cifs: Use iterate_and_advance*() routines directly for hashing

Replace the bespoke cifs iterators of ITER_BVEC and ITER_KVEC to do hashing
with iterate_and_advance_kernel() - a variant on iterate_and_advance() that
only supports kernel-internal ITER_* types and not UBUF/IOVEC types.

The bespoke ITER_XARRAY is left because we don't really want to be calling
crypto_shash_update() under the RCU read lock for large amounts of data;
besides, ITER_XARRAY is going to be phased out.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Steve French <sfrench@samba.org>
cc: Paulo Alcantara <pc@manguebit.com>
cc: Tom Talpey <tom@talpey.com>
cc: Enzo Matsumiya <ematsumiya@suse.de>
cc: linux-cifs@vger.kernel.org
Link: https://lore.kernel.org/r/20240814203850.2240469-24-dhowells@redhat.com/ # v2
Signed-off-by: Christian Brauner <brauner@kernel.org>

1 files changed, 23 insertions, 86 deletions

diff --git a/fs/smb/client/cifsencrypt.c b/fs/smb/client/cifsencrypt.c
index 6322f0f68a17..991a1ab047e7 100644
--- a/fs/smb/client/cifsencrypt.c
+++ b/fs/smb/client/cifsencrypt.c
@@ -21,83 +21,11 @@
 #include <linux/random.h>
 #include <linux/highmem.h>
 #include <linux/fips.h>
+#include <linux/iov_iter.h>
 #include "../common/arc4.h"
 #include <crypto/aead.h>
 
 /*
- * Hash data from a BVEC-type iterator.
- */
-static int cifs_shash_bvec(const struct iov_iter *iter, ssize_t maxsize,
-			   struct shash_desc *shash)
-{
-	const struct bio_vec *bv = iter->bvec;
-	unsigned long start = iter->iov_offset;
-	unsigned int i;
-	void *p;
-	int ret;
-
-	for (i = 0; i < iter->nr_segs; i++) {
-		size_t off, len;
-
-		len = bv[i].bv_len;
-		if (start >= len) {
-			start -= len;
-			continue;
-		}
-
-		len = min_t(size_t, maxsize, len - start);
-		off = bv[i].bv_offset + start;
-
-		p = kmap_local_page(bv[i].bv_page);
-		ret = crypto_shash_update(shash, p + off, len);
-		kunmap_local(p);
-		if (ret < 0)
-			return ret;
-
-		maxsize -= len;
-		if (maxsize <= 0)
-			break;
-		start = 0;
-	}
-
-	return 0;
-}
-
-/*
- * Hash data from a KVEC-type iterator.
- */
-static int cifs_shash_kvec(const struct iov_iter *iter, ssize_t maxsize,
-			   struct shash_desc *shash)
-{
-	const struct kvec *kv = iter->kvec;
-	unsigned long start = iter->iov_offset;
-	unsigned int i;
-	int ret;
-
-	for (i = 0; i < iter->nr_segs; i++) {
-		size_t len;
-
-		len = kv[i].iov_len;
-		if (start >= len) {
-			start -= len;
-			continue;
-		}
-
-		len = min_t(size_t, maxsize, len - start);
-		ret = crypto_shash_update(shash, kv[i].iov_base + start, len);
-		if (ret < 0)
-			return ret;
-		maxsize -= len;
-
-		if (maxsize <= 0)
-			break;
-		start = 0;
-	}
-
-	return 0;
-}
-
-/*
  * Hash data from an XARRAY-type iterator.
  */
 static ssize_t cifs_shash_xarray(const struct iov_iter *iter, ssize_t maxsize,
@@ -145,27 +73,36 @@ static ssize_t cifs_shash_xarray(const struct iov_iter *iter, ssize_t maxsize,
 	return 0;
 }
 
+static size_t cifs_shash_step(void *iter_base, size_t progress, size_t len,
+			      void *priv, void *priv2)
+{
+	struct shash_desc *shash = priv;
+	int ret, *pret = priv2;
+
+	ret = crypto_shash_update(shash, iter_base, len);
+	if (ret < 0) {
+		*pret = ret;
+		return len;
+	}
+	return 0;
+}
+
 /*
  * Pass the data from an iterator into a hash.
  */
 static int cifs_shash_iter(const struct iov_iter *iter, size_t maxsize,
 			   struct shash_desc *shash)
 {
-	if (maxsize == 0)
-		return 0;
+	struct iov_iter tmp_iter = *iter;
+	int err = -EIO;
 
-	switch (iov_iter_type(iter)) {
-	case ITER_BVEC:
-		return cifs_shash_bvec(iter, maxsize, shash);
-	case ITER_KVEC:
-		return cifs_shash_kvec(iter, maxsize, shash);
-	case ITER_XARRAY:
+	if (iov_iter_type(iter) == ITER_XARRAY)
 		return cifs_shash_xarray(iter, maxsize, shash);
-	default:
-		pr_err("cifs_shash_iter(%u) unsupported\n", iov_iter_type(iter));
-		WARN_ON_ONCE(1);
-		return -EIO;
-	}
+
+	if (iterate_and_advance_kernel(&tmp_iter, maxsize, shash, &err,
+				       cifs_shash_step) != maxsize)
+		return err;
+	return 0;
 }
 
 int __cifs_calc_signature(struct smb_rqst *rqst,