fs_parse: add uid & gid option option parsing helpers

Multiple filesystems take uid and gid as options, and the code to
create the ID from an integer and validate it is standard boilerplate
that can be moved into common helper functions, so do that for
consistency and less cut&paste.

This also helps avoid the buggy pattern noted by Seth Jenkins at
https://lore.kernel.org/lkml/CALxfFW4BXhEwxR0Q5LSkg-8Vb4r2MONKCcUCVioehXQKr35eHg@mail.gmail.com/
because uid/gid parsing will fail before any assignment in most
filesystems.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>
Link: https://lore.kernel.org/r/de859d0a-feb9-473d-a5e2-c195a3d47abb@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/Documentation/filesystems/mount_api.rst b/Documentation/filesystems/mount_api.rst
index 9aaf6ef75eb53b1ef25f20a0641479c48823183e..317934c9e8fcac0049fbbcc59f7759713d4ca55d 100644 (file)
--- a/Documentation/filesystems/mount_api.rst
+++ b/Documentation/filesystems/mount_api.rst
@@ -645,6 +645,8 @@ The members are as follows:
        fs_param_is_blockdev    Blockdev path           * Needs lookup
        fs_param_is_path        Path                    * Needs lookup
        fs_param_is_fd          File descriptor         result->int_32
+       fs_param_is_uid         User ID (u32)           result->uid
+       fs_param_is_gid         Group ID (u32)          result->gid
        ======================= ======================= =====================
 
      Note that if the value is of fs_param_is_bool type, fs_parse() will try
@@ -678,6 +680,8 @@ The members are as follows:
        fsparam_bdev()          fs_param_is_blockdev
        fsparam_path()          fs_param_is_path
        fsparam_fd()            fs_param_is_fd
+       fsparam_uid()           fs_param_is_uid
+       fsparam_gid()           fs_param_is_gid
        ======================= ===============================================
 
      all of which take two arguments, name string and option number - for
@@ -784,8 +788,9 @@ process the parameters it is given.
      option number (which it returns).
 
      If successful, and if the parameter type indicates the result is a
-     boolean, integer or enum type, the value is converted by this function and
-     the result stored in result->{boolean,int_32,uint_32,uint_64}.
+     boolean, integer, enum, uid, or gid type, the value is converted by this
+     function and the result stored in
+     result->{boolean,int_32,uint_32,uint_64,uid,gid}.
 
      If a match isn't initially made, the key is prefixed with "no" and no
      value is present then an attempt will be made to look up the key with the

diff --git a/fs/fs_parser.c b/fs/fs_parser.c
index a4d6ca0b8971e65b1e3b832d591ac01bad10f8d8..24727ec34e5aa434364e87879cccf9fe1ec19d37 100644 (file)
--- a/fs/fs_parser.c
+++ b/fs/fs_parser.c
@@ -308,6 +308,40 @@ int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
 }
 EXPORT_SYMBOL(fs_param_is_fd);
 
+int fs_param_is_uid(struct p_log *log, const struct fs_parameter_spec *p,
+                   struct fs_parameter *param, struct fs_parse_result *result)
+{
+       kuid_t uid;
+
+       if (fs_param_is_u32(log, p, param, result) != 0)
+               return fs_param_bad_value(log, param);
+
+       uid = make_kuid(current_user_ns(), result->uint_32);
+       if (!uid_valid(uid))
+               return inval_plog(log, "Invalid uid '%s'", param->string);
+
+       result->uid = uid;
+       return 0;
+}
+EXPORT_SYMBOL(fs_param_is_uid);
+
+int fs_param_is_gid(struct p_log *log, const struct fs_parameter_spec *p,
+                   struct fs_parameter *param, struct fs_parse_result *result)
+{
+       kgid_t gid;
+
+       if (fs_param_is_u32(log, p, param, result) != 0)
+               return fs_param_bad_value(log, param);
+
+       gid = make_kgid(current_user_ns(), result->uint_32);
+       if (!gid_valid(gid))
+               return inval_plog(log, "Invalid gid '%s'", param->string);
+
+       result->gid = gid;
+       return 0;
+}
+EXPORT_SYMBOL(fs_param_is_gid);
+
 int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
                  struct fs_parameter *param, struct fs_parse_result *result)
 {

diff --git a/include/linux/fs_parser.h b/include/linux/fs_parser.h
index d3350979115f0a050efe9ee0ad7619c32b5c2f91..6cf713a7e6c6fc2402a68c87036264eaed921432 100644 (file)
--- a/include/linux/fs_parser.h
+++ b/include/linux/fs_parser.h
@@ -28,7 +28,7 @@ typedef int fs_param_type(struct p_log *,
  */
 fs_param_type fs_param_is_bool, fs_param_is_u32, fs_param_is_s32, fs_param_is_u64,
        fs_param_is_enum, fs_param_is_string, fs_param_is_blob, fs_param_is_blockdev,
-       fs_param_is_path, fs_param_is_fd;
+       fs_param_is_path, fs_param_is_fd, fs_param_is_uid, fs_param_is_gid;
 
 /*
  * Specification of the type of value a parameter wants.
@@ -57,6 +57,8 @@ struct fs_parse_result {
                int             int_32;         /* For spec_s32/spec_enum */
                unsigned int    uint_32;        /* For spec_u32{,_octal,_hex}/spec_enum */
                u64             uint_64;        /* For spec_u64 */
+               kuid_t          uid;
+               kgid_t          gid;
        };
 };
 
@@ -131,6 +133,8 @@ static inline bool fs_validate_description(const char *name,
 #define fsparam_bdev(NAME, OPT)        __fsparam(fs_param_is_blockdev, NAME, OPT, 0, NULL)
 #define fsparam_path(NAME, OPT)        __fsparam(fs_param_is_path, NAME, OPT, 0, NULL)
 #define fsparam_fd(NAME, OPT)  __fsparam(fs_param_is_fd, NAME, OPT, 0, NULL)
+#define fsparam_uid(NAME, OPT) __fsparam(fs_param_is_uid, NAME, OPT, 0, NULL)
+#define fsparam_gid(NAME, OPT) __fsparam(fs_param_is_gid, NAME, OPT, 0, NULL)
 
 /* String parameter that allows empty argument */
 #define fsparam_string_empty(NAME, OPT) \