userns: Convert tmpfs to use kuid and kgid where appropriate

Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>

include/linux/shmem_fs.h

@@ -28,8 +28,8 @@ struct shmem_sb_info {
 	unsigned long max_inodes;   /* How many inodes are allowed */
 	unsigned long free_inodes;  /* How many are left for allocation */
 	spinlock_t stat_lock;	    /* Serialize shmem_sb_info changes */
-	uid_t uid;		    /* Mount uid for root directory */
-	gid_t gid;		    /* Mount gid for root directory */
+	kuid_t uid;		    /* Mount uid for root directory */
+	kgid_t gid;		    /* Mount gid for root directory */
 	umode_t mode;		    /* Mount mode for root directory */
 	struct mempolicy *mpol;     /* default memory policy for mappings */
 };

init/Kconfig

@@ -953,7 +953,6 @@ config UIDGID_CONVERTED
 	depends on REISERFS_FS = n
 	depends on SQUASHFS = n
 	depends on SYSV_FS = n
-	depends on TMPFS = n
 	depends on UBIFS_FS = n
 	depends on UDF_FS = n
 	depends on UFS_FS = n

mm/shmem.c

@@ -2075,6 +2075,8 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
 			       bool remount)
 {
 	char *this_char, *value, *rest;
+	uid_t uid;
+	gid_t gid;
 
 	while (options != NULL) {
 		this_char = options;
@@ -2134,15 +2136,21 @@ static int shmem_parse_options(char *options, struct shmem_sb_info *sbinfo,
 		} else if (!strcmp(this_char,"uid")) {
 			if (remount)
 				continue;
-			sbinfo->uid = simple_strtoul(value, &rest, 0);
+			uid = simple_strtoul(value, &rest, 0);
 			if (*rest)
 				goto bad_val;
+			sbinfo->uid = make_kuid(current_user_ns(), uid);
+			if (!uid_valid(sbinfo->uid))
+				goto bad_val;
 		} else if (!strcmp(this_char,"gid")) {
 			if (remount)
 				continue;
-			sbinfo->gid = simple_strtoul(value, &rest, 0);
+			gid = simple_strtoul(value, &rest, 0);
 			if (*rest)
 				goto bad_val;
+			sbinfo->gid = make_kgid(current_user_ns(), gid);
+			if (!gid_valid(sbinfo->gid))
+				goto bad_val;
 		} else if (!strcmp(this_char,"mpol")) {
 			if (mpol_parse_str(value, &sbinfo->mpol, 1))
 				goto bad_val;
@@ -2210,10 +2218,12 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
 		seq_printf(seq, ",nr_inodes=%lu", sbinfo->max_inodes);
 	if (sbinfo->mode != (S_IRWXUGO | S_ISVTX))
 		seq_printf(seq, ",mode=%03ho", sbinfo->mode);
-	if (sbinfo->uid != 0)
-		seq_printf(seq, ",uid=%u", sbinfo->uid);
-	if (sbinfo->gid != 0)
-		seq_printf(seq, ",gid=%u", sbinfo->gid);
+	if (!uid_eq(sbinfo->uid, GLOBAL_ROOT_UID))
+		seq_printf(seq, ",uid=%u",
+				from_kuid_munged(&init_user_ns, sbinfo->uid));
+	if (!gid_eq(sbinfo->gid, GLOBAL_ROOT_GID))
+		seq_printf(seq, ",gid=%u",
+				from_kgid_munged(&init_user_ns, sbinfo->gid));
 	shmem_show_mpol(seq, sbinfo->mpol);
 	return 0;
 }