commit 0f89589a8c6f1033cb847a606517998efb0da8ee
author Al Viro <viro@zeniv.linux.org.uk> Tue Dec 17 14:15:04 2019 -0500
committer Al Viro <viro@zeniv.linux.org.uk> Fri Feb 07 00:10:29 2020 -0500
tree c20e5e8b71553ced5b592d6135a76cb975e12253
parent 7dc2993a9e51dd2eee955944efec65bef90265b7

Pass consistent param->type to fs_parse()

As it is, vfs_parse_fs_string() makes "foo" and "foo=" indistinguishable;
both get fs_value_is_string for ->type and NULL for ->string.  To make
it even more unpleasant, that combination is impossible to produce with
fsconfig().

Much saner rules would be
        "foo"           => fs_value_is_flag, NULL
	"foo="          => fs_value_is_string, ""
	"foo=bar"       => fs_value_is_string, "bar"
All cases are distinguishable, all results are expressable by fsconfig(),
->has_value checks are much simpler that way (to the point of the field
being useless) and quite a few regressions go away (gfs2 has no business
accepting -o nodebug=, for example).

Partially based upon patches from Miklos.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/fs_context.c

diff --git a/fs/fs_context.c b/fs/fs_context.c
index 138b5b4..9097421 100644
--- a/fs/fs_context.c
+++ b/fs/fs_context.c
@@ -175,14 +175,15 @@ int vfs_parse_fs_string(struct fs_context *fc, const char *key,
 
 	struct fs_parameter param = {
 		.key	= key,
-		.type	= fs_value_is_string,
+		.type	= fs_value_is_flag,
 		.size	= v_size,
 	};
 
-	if (v_size > 0) {
+	if (value) {
 		param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
 		if (!param.string)
 			return -ENOMEM;
+		param.type = fs_value_is_string;
 	}
 
 	ret = vfs_parse_fs_param(fc, &param);

fs/fs_parser.c

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index d1930ad..07ae041 100644
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -85,7 +85,6 @@ int fs_parse(struct fs_context *fc,
 	const struct fs_parameter_enum *e;
 	int ret = -ENOPARAM, b;
 
-	result->has_value = !!param->string;
 	result->negated = false;
 	result->uint_64 = 0;
 
@@ -95,7 +94,7 @@ int fs_parse(struct fs_context *fc,
 		 * "xxx" takes the "no"-form negative - but only if there
 		 * wasn't an value.
 		 */
-		if (result->has_value)
+		if (param->type != fs_value_is_flag)
 			goto unknown_parameter;
 		if (param->key[0] != 'n' || param->key[1] != 'o' || !param->key[2])
 			goto unknown_parameter;
@@ -127,14 +126,18 @@ int fs_parse(struct fs_context *fc,
 	case fs_param_is_u64:
 	case fs_param_is_enum:
 	case fs_param_is_string:
-		if (param->type != fs_value_is_string)
-			goto bad_value;
-		if (!result->has_value) {
+		if (param->type == fs_value_is_string) {
+			if (p->flags & fs_param_v_optional)
+				break;
+			if (!*param->string)
+				goto bad_value;
+			break;
+		}
+		if (param->type == fs_value_is_flag) {
 			if (p->flags & fs_param_v_optional)
 				goto okay;
-			goto bad_value;
 		}
-		/* Fall through */
+		goto bad_value;
 	default:
 		break;
 	}
@@ -144,8 +147,7 @@ int fs_parse(struct fs_context *fc,
 	 */
 	switch (p->type) {
 	case fs_param_is_flag:
-		if (param->type != fs_value_is_flag &&
-		    (param->type != fs_value_is_string || result->has_value))
+		if (param->type != fs_value_is_flag)
 			return invalf(fc, "%s: Unexpected value for '%s'",
 				      desc->name, param->key);
 		result->boolean = true;
@@ -206,9 +208,6 @@ int fs_parse(struct fs_context *fc,
 	case fs_param_is_fd: {
 		switch (param->type) {
 		case fs_value_is_string:
-			if (!result->has_value)
-				goto bad_value;
-
 			ret = kstrtouint(param->string, 0, &result->uint_32);
 			break;
 		case fs_value_is_file: