Revert "ethtool: Fix mod state of verbose no_mask bitset"

This reverts commit 108a36d.

It was reported that this fix breaks the possibility to remove existing WoL
flags. For example:
~$ ethtool lan2
...
        Supports Wake-on: pg
        Wake-on: d
...
~$ ethtool -s lan2 wol gp
~$ ethtool lan2
...
        Wake-on: pg
...
~$ ethtool -s lan2 wol d
~$ ethtool lan2
...
        Wake-on: pg
...

This worked correctly before this commit because we were always updating
a zero bitmap (since commit 6699170 ("ethtool: fix application of
verbose no_mask bitset"), that is) so that the rest was left zero
naturally. But now the 1->0 change (old_val is true, bit not present in
netlink nest) no longer works.

Reported-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reported-by: Michal Kubecek <mkubecek@suse.cz>
Closes: https://lore.kernel.org/netdev/20231019095140.l6fffnszraeb6iiw@lion.mk-sys.cz/
Cc: stable@vger.kernel.org
Fixes: 108a36d ("ethtool: Fix mod state of verbose no_mask bitset")
Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Reviewed-by: Michal Kubecek <mkubecek@suse.cz>
Link: https://lore.kernel.org/r/20231019-feature_ptp_bitset_fix-v1-1-70f3c429a221@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ethtool/bitset.c

@@ -431,10 +431,8 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 			      ethnl_string_array_t names,
 			      struct netlink_ext_ack *extack, bool *mod)
 {
-	u32 *orig_bitmap, *saved_bitmap = NULL;
 	struct nlattr *bit_attr;
 	bool no_mask;
-	bool dummy;
 	int rem;
 	int ret;
 
@@ -450,22 +448,8 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 	}
 
 	no_mask = tb[ETHTOOL_A_BITSET_NOMASK];
-	if (no_mask) {
-		unsigned int nwords = DIV_ROUND_UP(nbits, 32);
-		unsigned int nbytes = nwords * sizeof(u32);
-
-		/* The bitmap size is only the size of the map part without
-		 * its mask part.
-		 */
-		saved_bitmap = kcalloc(nwords, sizeof(u32), GFP_KERNEL);
-		if (!saved_bitmap)
-			return -ENOMEM;
-		memcpy(saved_bitmap, bitmap, nbytes);
-		ethnl_bitmap32_clear(bitmap, 0, nbits, &dummy);
-		orig_bitmap = saved_bitmap;
-	} else {
-		orig_bitmap = bitmap;
-	}
+	if (no_mask)
+		ethnl_bitmap32_clear(bitmap, 0, nbits, mod);
 
 	nla_for_each_nested(bit_attr, tb[ETHTOOL_A_BITSET_BITS], rem) {
 		bool old_val, new_val;
@@ -474,14 +458,13 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 		if (nla_type(bit_attr) != ETHTOOL_A_BITSET_BITS_BIT) {
 			NL_SET_ERR_MSG_ATTR(extack, bit_attr,
 					    "only ETHTOOL_A_BITSET_BITS_BIT allowed in ETHTOOL_A_BITSET_BITS");
-			ret = -EINVAL;
-			goto out;
+			return -EINVAL;
 		}
 		ret = ethnl_parse_bit(&idx, &new_val, nbits, bit_attr, no_mask,
 				      names, extack);
 		if (ret < 0)
-			goto out;
-		old_val = orig_bitmap[idx / 32] & ((u32)1 << (idx % 32));
+			return ret;
+		old_val = bitmap[idx / 32] & ((u32)1 << (idx % 32));
 		if (new_val != old_val) {
 			if (new_val)
 				bitmap[idx / 32] |= ((u32)1 << (idx % 32));
@@ -491,10 +474,7 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned int nbits,
 		}
 	}
 
-	ret = 0;
-out:
-	kfree(saved_bitmap);
-	return ret;
+	return 0;
 }
 
 static int ethnl_compact_sanity_checks(unsigned int nbits,