fs_parse: allow parameter value to be empty

Allow parameter value to be empty by specifying fs_param_can_be_empty
flag.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Link: https://lore.kernel.org/r/20211027141857.33657-2-lczerner@redhat.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index 3df07c0..ed40ce5 100644 (file)
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -199,6 +199,8 @@ int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
        int b;
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
+       if (!*param->string && (p->flags & fs_param_can_be_empty))
+               return 0;
        b = lookup_constant(bool_names, param->string, -1);
        if (b == -1)
                return fs_param_bad_value(log, param);
@@ -211,8 +213,11 @@ int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
 {
        int base = (unsigned long)p->data;
-       if (param->type != fs_value_is_string ||
-           kstrtouint(param->string, base, &result->uint_32) < 0)
+       if (param->type != fs_value_is_string)
+               return fs_param_bad_value(log, param);
+       if (!*param->string && (p->flags & fs_param_can_be_empty))
+               return 0;
+       if (kstrtouint(param->string, base, &result->uint_32) < 0)
                return fs_param_bad_value(log, param);
        return 0;
 }
@@ -221,8 +226,11 @@ EXPORT_SYMBOL(fs_param_is_u32);
 int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
 {
-       if (param->type != fs_value_is_string ||
-           kstrtoint(param->string, 0, &result->int_32) < 0)
+       if (param->type != fs_value_is_string)
+               return fs_param_bad_value(log, param);
+       if (!*param->string && (p->flags & fs_param_can_be_empty))
+               return 0;
+       if (kstrtoint(param->string, 0, &result->int_32) < 0)
                return fs_param_bad_value(log, param);
        return 0;
 }
@@ -231,8 +239,11 @@ EXPORT_SYMBOL(fs_param_is_s32);
 int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
 {
-       if (param->type != fs_value_is_string ||
-           kstrtoull(param->string, 0, &result->uint_64) < 0)
+       if (param->type != fs_value_is_string)
+               return fs_param_bad_value(log, param);
+       if (!*param->string && (p->flags & fs_param_can_be_empty))
+               return 0;
+       if (kstrtoull(param->string, 0, &result->uint_64) < 0)
                return fs_param_bad_value(log, param);
        return 0;
 }
@@ -244,6 +255,8 @@ int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
        const struct constant_table *c;
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
+       if (!*param->string && (p->flags & fs_param_can_be_empty))
+               return 0;
        c = __lookup_constant(p->data, param->string);
        if (!c)
                return fs_param_bad_value(log, param);
@@ -255,7 +268,8 @@ EXPORT_SYMBOL(fs_param_is_enum);
 int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
                       struct fs_parameter *param, struct fs_parse_result *result)
 {
-       if (param->type != fs_value_is_string || !*param->string)
+       if (param->type != fs_value_is_string ||
+           (!*param->string && !(p->flags & fs_param_can_be_empty)))
                return fs_param_bad_value(log, param);
        return 0;
 }
@@ -275,7 +289,8 @@ int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
 {
        switch (param->type) {
        case fs_value_is_string:
-               if (kstrtouint(param->string, 0, &result->uint_32) < 0)
+               if ((!*param->string && !(p->flags & fs_param_can_be_empty)) ||
+                   kstrtouint(param->string, 0, &result->uint_32) < 0)
                        break;
                if (result->uint_32 <= INT_MAX)
                        return 0;

diff --git a/include/linux/fs_parser.h b/include/linux/fs_parser.h
index aab0ffc..f103c91 100644 (file)
--- a/include/linux/fs_parser.h
+++ b/include/linux/fs_parser.h
@@ -42,7 +42,7 @@ struct fs_parameter_spec {
        u8                      opt;    /* Option number (returned by fs_parse()) */
        unsigned short          flags;
 #define fs_param_neg_with_no   0x0002  /* "noxxx" is negative param */
-#define fs_param_neg_with_empty        0x0004  /* "xxx=" is negative param */
+#define fs_param_can_be_empty  0x0004  /* "xxx=" is allowed */
 #define fs_param_deprecated    0x0008  /* The param is deprecated */
        const void              *data;
 };