[PATCH] exfat: add ioctls for accessing attributes

[PATCH] exfat: add ioctls for accessing attributes

[Jan Cincera]

Add GET and SET attributes ioctls to enable attribute modification.
We already do this in FAT and a few userspace utils made for it would
benefit from this also working on exFAT, namely fatattr.

Signed-off-by: Jan Cincera <hcincera@gmail.com>
---
 fs/exfat/exfat_fs.h |  6 +++
 fs/exfat/file.c     | 97 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 103 insertions(+)

diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
index 729ada9e26e8..ebe8c4b928f4 100644
--- a/fs/exfat/exfat_fs.h
+++ b/fs/exfat/exfat_fs.h
@@ -149,6 +149,12 @@ enum {
 #define DIR_CACHE_SIZE		\
 	(DIV_ROUND_UP(EXFAT_DEN_TO_B(ES_MAX_ENTRY_NUM), SECTOR_SIZE) + 1)
 
+/*
+ * attribute ioctls, same as their FAT equivalents.
+ */
+#define EXFAT_IOCTL_GET_ATTRIBUTES	_IOR('r', 0x10, __u32)
+#define EXFAT_IOCTL_SET_ATTRIBUTES	_IOW('r', 0x11, __u32)
+
 struct exfat_dentry_namebuf {
 	char *lfn;
 	int lfnbuf_len; /* usually MAX_UNINAME_BUF_SIZE */
diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 3cbd270e0cba..b358acbead27 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -8,6 +8,8 @@
 #include <linux/cred.h>
 #include <linux/buffer_head.h>
 #include <linux/blkdev.h>
+#include <linux/fsnotify.h>
+#include <linux/security.h>
 
 #include "exfat_raw.h"
 #include "exfat_fs.h"
@@ -316,6 +318,96 @@ int exfat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
 	return error;
 }
 
+/*
+ * modified ioctls from fat/file.c by Welmer Almesberger
+ */
+static int exfat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
+{
+	u32 attr;
+
+	inode_lock_shared(inode);
+	attr = exfat_make_attr(inode);
+	inode_unlock_shared(inode);
+
+	return put_user(attr, user_attr);
+}
+
+static int exfat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
+{
+	struct inode *inode = file_inode(file);
+	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
+	int is_dir = S_ISDIR(inode->i_mode);
+	u32 attr, oldattr;
+	struct iattr ia;
+	int err;
+
+	err = get_user(attr, user_attr);
+	if (err)
+		goto out;
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+	inode_lock(inode);
+
+	/*
+	 * ATTR_VOLUME and ATTR_SUBDIR cannot be changed; this also
+	 * prevents the user from turning us into a VFAT
+	 * longname entry.  Also, we obviously can't set
+	 * any of the NTFS attributes in the high 24 bits.
+	 */
+	attr &= 0xff & ~(ATTR_VOLUME | ATTR_SUBDIR);
+	/* Merge in ATTR_VOLUME and ATTR_DIR */
+	attr |= (EXFAT_I(inode)->attr & ATTR_VOLUME) |
+		(is_dir ? ATTR_SUBDIR : 0);
+	oldattr = exfat_make_attr(inode);
+
+	/* Equivalent to a chmod() */
+	ia.ia_valid = ATTR_MODE | ATTR_CTIME;
+	ia.ia_ctime = current_time(inode);
+	if (is_dir)
+		ia.ia_mode = exfat_make_mode(sbi, attr, 0777);
+	else
+		ia.ia_mode = exfat_make_mode(sbi, attr, 0666 | (inode->i_mode & 0111));
+
+	/* The root directory has no attributes */
+	if (inode->i_ino == EXFAT_ROOT_INO && attr != ATTR_SUBDIR) {
+		err = -EINVAL;
+		goto out_unlock_inode;
+	}
+
+	if (((attr | oldattr) & ATTR_SYSTEM) &&
+	    !capable(CAP_LINUX_IMMUTABLE)) {
+		err = -EPERM;
+		goto out_unlock_inode;
+	}
+
+	/*
+	 * The security check is questionable...  We single
+	 * out the RO attribute for checking by the security
+	 * module, just because it maps to a file mode.
+	 */
+	err = security_inode_setattr(file_mnt_idmap(file),
+				     file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	/* This MUST be done before doing anything irreversible... */
+	err = exfat_setattr(file_mnt_idmap(file), file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	fsnotify_change(file->f_path.dentry, ia.ia_valid);
+
+	exfat_save_attr(inode, attr);
+	mark_inode_dirty(inode);
+out_unlock_inode:
+	inode_unlock(inode);
+	mnt_drop_write_file(file);
+out:
+	return err;
+}
+
 static int exfat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 {
 	struct fstrim_range range;
@@ -346,8 +438,13 @@ static int exfat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = file_inode(filp);
+	u32 __user *user_attr = (u32 __user *)arg;
 
 	switch (cmd) {
+	case EXFAT_IOCTL_GET_ATTRIBUTES:
+		return exfat_ioctl_get_attributes(inode, user_attr);
+	case EXFAT_IOCTL_SET_ATTRIBUTES:
+		return exfat_ioctl_set_attributes(filp, user_attr);
 	case FITRIM:
 		return exfat_ioctl_fitrim(inode, arg);
 	default:
-- 
2.40.1

Re: [PATCH] exfat: add ioctls for accessing attributes

[Namjae Jeon]

2023-08-16 3:29 GMT+09:00, Jan Cincera <hcincera@gmail.com>:
> Add GET and SET attributes ioctls to enable attribute modification.
> We already do this in FAT and a few userspace utils made for it would
> benefit from this also working on exFAT, namely fatattr.
>
> Signed-off-by: Jan Cincera <hcincera@gmail.com>
> ---
>  fs/exfat/exfat_fs.h |  6 +++
>  fs/exfat/file.c     | 97 +++++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 103 insertions(+)
>
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
> index 729ada9e26e8..ebe8c4b928f4 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -149,6 +149,12 @@ enum {
>  #define DIR_CACHE_SIZE		\
>  	(DIV_ROUND_UP(EXFAT_DEN_TO_B(ES_MAX_ENTRY_NUM), SECTOR_SIZE) + 1)
>
> +/*
> + * attribute ioctls, same as their FAT equivalents.
> + */
> +#define EXFAT_IOCTL_GET_ATTRIBUTES	_IOR('r', 0x10, __u32)
> +#define EXFAT_IOCTL_SET_ATTRIBUTES	_IOW('r', 0x11, __u32)
> +
>  struct exfat_dentry_namebuf {
>  	char *lfn;
>  	int lfnbuf_len; /* usually MAX_UNINAME_BUF_SIZE */
> diff --git a/fs/exfat/file.c b/fs/exfat/file.c
> index 3cbd270e0cba..b358acbead27 100644
> --- a/fs/exfat/file.c
> +++ b/fs/exfat/file.c
> @@ -8,6 +8,8 @@
>  #include <linux/cred.h>
>  #include <linux/buffer_head.h>
>  #include <linux/blkdev.h>
> +#include <linux/fsnotify.h>
> +#include <linux/security.h>
>
>  #include "exfat_raw.h"
>  #include "exfat_fs.h"
> @@ -316,6 +318,96 @@ int exfat_setattr(struct mnt_idmap *idmap, struct
> dentry *dentry,
>  	return error;
>  }
>
> +/*
> + * modified ioctls from fat/file.c by Welmer Almesberger
> + */
> +static int exfat_ioctl_get_attributes(struct inode *inode, u32 __user
> *user_attr)
> +{
> +	u32 attr;
> +
> +	inode_lock_shared(inode);
> +	attr = exfat_make_attr(inode);
> +	inode_unlock_shared(inode);
> +
> +	return put_user(attr, user_attr);
> +}
> +
> +static int exfat_ioctl_set_attributes(struct file *file, u32 __user
> *user_attr)
> +{
> +	struct inode *inode = file_inode(file);
> +	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
> +	int is_dir = S_ISDIR(inode->i_mode);
> +	u32 attr, oldattr;
> +	struct iattr ia;
> +	int err;
> +
> +	err = get_user(attr, user_attr);
> +	if (err)
> +		goto out;
> +
> +	err = mnt_want_write_file(file);
> +	if (err)
> +		goto out;
> +	inode_lock(inode);
> +
> +	/*
> +	 * ATTR_VOLUME and ATTR_SUBDIR cannot be changed; this also
> +	 * prevents the user from turning us into a VFAT
> +	 * longname entry.  Also, we obviously can't set
> +	 * any of the NTFS attributes in the high 24 bits.
> +	 */
This comments seems to be wrong. In particular, The comment about
longfilename and ATTR_VOLUME for vfat should be removed.

> +	attr &= 0xff & ~(ATTR_VOLUME | ATTR_SUBDIR);
> +	/* Merge in ATTR_VOLUME and ATTR_DIR */
> +	attr |= (EXFAT_I(inode)->attr & ATTR_VOLUME) |
> +		(is_dir ? ATTR_SUBDIR : 0);
We need to mask exfat file attribute bits like the following not to
set reserved fields(+ ATTR_SUBDIR). And there is no ATTR_VOLUME field
in exfat.

Table 28 FileAttributes Field Structure
ReadOnly        0	1	This field is mandatory and conforms to the MS-DOS
definition.
Hidden             1     	1	This field is mandatory and conforms to
the MS-DOS definition.
System            2	1	This field is mandatory and conforms to the
MS-DOS definition.
Reserved1       3	1	This field is mandatory and its contents are reserved.
Directory          4	1	This field is mandatory and conforms to the
MS-DOS definition.
Archive            5	1	This field is mandatory and conforms to the
MS-DOS definition.
Reserved2	6	10	This field is mandatory and its contents are reserved.

Thanks.