f2fs: support FS_IOC_{GET,SET}FSLABEL

Support two generic fs ioctls FS_IOC_{GET,SET}FSLABEL, letting
f2fs pass generic/492 testcase.

Fixes were made by Eric where:
 - f2fs: fix buffer overruns in FS_IOC_{GET, SET}FSLABEL
   utf16s_to_utf8s() and utf8s_to_utf16s() take the number of characters,
   not the number of bytes.

 - f2fs: fix copying too many bytes in FS_IOC_SETFSLABEL
   Userspace provides a null-terminated string, so don't assume that the
   full FSLABEL_MAX bytes can always be copied.

 - f2fs: add missing authorization check in FS_IOC_SETFSLABEL
   FS_IOC_SETFSLABEL modifies the filesystem superblock, so it shouldn't be
   allowed to regular users.  Require CAP_SYS_ADMIN, like xfs and btrfs do.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

2 files changed, 72 insertions, 0 deletions

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 09ad4116d635..d2b718e33f88 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -418,6 +418,9 @@ static inline bool __has_cursum_space(struct f2fs_journal *journal,
 #define F2FS_IOC_PRECACHE_EXTENTS       _IO(F2FS_IOCTL_MAGIC, 15)
 #define F2FS_IOC_RESIZE_FS              _IOW(F2FS_IOCTL_MAGIC, 16, __u64)
 
+#define F2FS_IOC_GET_VOLUME_NAME        FS_IOC_GETFSLABEL
+#define F2FS_IOC_SET_VOLUME_NAME        FS_IOC_SETFSLABEL
+
 #define F2FS_IOC_SET_ENCRYPTION_POLICY  FS_IOC_SET_ENCRYPTION_POLICY
 #define F2FS_IOC_GET_ENCRYPTION_POLICY  FS_IOC_GET_ENCRYPTION_POLICY
 #define F2FS_IOC_GET_ENCRYPTION_PWSALT  FS_IOC_GET_ENCRYPTION_PWSALT
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index b1f38f2795bc..344e0bd638e5 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -20,6 +20,7 @@
 #include <linux/uio.h>
 #include <linux/uuid.h>
 #include <linux/file.h>
+#include <linux/nls.h>
 
 #include "f2fs.h"
 #include "node.h"
@@ -3081,6 +3082,68 @@ static int f2fs_ioc_resize_fs(struct file *filp, unsigned long arg)
         return ret;
 }
 
+static int f2fs_get_volume_name(struct file *filp, unsigned long arg)
+{
+        struct inode *inode = file_inode(filp);
+        struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+        char *vbuf;
+        int count;
+        int err = 0;
+
+        vbuf = f2fs_kzalloc(sbi, MAX_VOLUME_NAME, GFP_KERNEL);
+        if (!vbuf)
+                return -ENOMEM;
+
+        down_read(&sbi->sb_lock);
+        count = utf16s_to_utf8s(sbi->raw_super->volume_name,
+                        ARRAY_SIZE(sbi->raw_super->volume_name),
+                        UTF16_LITTLE_ENDIAN, vbuf, MAX_VOLUME_NAME);
+        up_read(&sbi->sb_lock);
+
+        if (copy_to_user((char __user *)arg, vbuf,
+                                min(FSLABEL_MAX, count)))
+                err = -EFAULT;
+
+        kvfree(vbuf);
+        return err;
+}
+
+static int f2fs_set_volume_name(struct file *filp, unsigned long arg)
+{
+        struct inode *inode = file_inode(filp);
+        struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+        char *vbuf;
+        int err = 0;
+
+        if (!capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        vbuf = strndup_user((const char __user *)arg, FSLABEL_MAX);
+        if (IS_ERR(vbuf))
+                return PTR_ERR(vbuf);
+
+        err = mnt_want_write_file(filp);
+        if (err)
+                goto out;
+
+        down_write(&sbi->sb_lock);
+
+        memset(sbi->raw_super->volume_name, 0,
+                        sizeof(sbi->raw_super->volume_name));
+        utf8s_to_utf16s(vbuf, strlen(vbuf), UTF16_LITTLE_ENDIAN,
+                        sbi->raw_super->volume_name,
+                        ARRAY_SIZE(sbi->raw_super->volume_name));
+
+        err = f2fs_commit_super(sbi, false);
+
+        up_write(&sbi->sb_lock);
+
+        mnt_drop_write_file(filp);
+out:
+        kfree(vbuf);
+        return err;
+}
+
 long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
         int ret;
@@ -3144,6 +3207,10 @@ long f2fs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                 return f2fs_ioc_precache_extents(filp, arg);
         case F2FS_IOC_RESIZE_FS:
                 return f2fs_ioc_resize_fs(filp, arg);
+        case F2FS_IOC_GET_VOLUME_NAME:
+                return f2fs_get_volume_name(filp, arg);
+        case F2FS_IOC_SET_VOLUME_NAME:
+                return f2fs_set_volume_name(filp, arg);
         default:
                 return -ENOTTY;
         }
@@ -3253,6 +3320,8 @@ long f2fs_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
         case F2FS_IOC_SET_PIN_FILE:
         case F2FS_IOC_PRECACHE_EXTENTS:
         case F2FS_IOC_RESIZE_FS:
+        case F2FS_IOC_GET_VOLUME_NAME:
+        case F2FS_IOC_SET_VOLUME_NAME:
                 break;
         default:
                 return -ENOIOCTLCMD;