Commit 9183482f authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Linus Torvalds

fat: Fix ATTR_RO in the case of (~umask & S_WUGO) == 0

If inode->i_mode doesn't have S_WUGO, current code assumes it means
ATTR_RO.  However, if (~[ufd]mask & S_WUGO) == 0, inode->i_mode can't
hold S_WUGO. Therefore the updated directory entry will always have

This adds fat_mode_can_hold_ro() to check it. And if inode->i_mode
can't hold, uses -i_attrs to hold ATTR_RO instead.

With this, we don't set ATTR_RO unless users change it via ioctl() if
(~[ufd]mask & S_WUGO) == 0.

And on FAT_IOCTL_GET_ATTRIBUTES path, this adds ->i_mutex to it for
not returning the partially updated attributes by FAT_IOCTL_SET_ATTRIBUTES
to userland.
Signed-off-by: default avatarOGAWA Hirofumi <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 9c0aa1b8
......@@ -117,6 +117,25 @@ static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
return container_of(inode, struct msdos_inode_info, vfs_inode);
* If ->i_mode can't hold S_IWUGO (i.e. ATTR_RO), we use ->i_attrs to
* save ATTR_RO instead of ->i_mode.
static inline int fat_mode_can_hold_ro(struct inode *inode)
struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
mode_t mask;
if (S_ISDIR(inode->i_mode))
mask = ~sbi->options.fs_dmask;
mask = ~sbi->options.fs_fmask;
if (!(mask & S_IWUGO))
return 0;
return 1;
/* Convert attribute bits and a mask to the UNIX mode. */
static inline mode_t fat_make_mode(struct msdos_sb_info *sbi,
u8 attrs, mode_t mode)
......@@ -133,14 +152,20 @@ static inline mode_t fat_make_mode(struct msdos_sb_info *sbi,
/* Return the FAT attribute byte for this inode */
static inline u8 fat_make_attrs(struct inode *inode)
return ((inode->i_mode & S_IWUGO) ? ATTR_NONE : ATTR_RO) |
(S_ISDIR(inode->i_mode) ? ATTR_DIR : ATTR_NONE) |
u8 attrs = MSDOS_I(inode)->i_attrs;
if (S_ISDIR(inode->i_mode))
attrs |= ATTR_DIR;
if (fat_mode_can_hold_ro(inode) && !(inode->i_mode & S_IWUGO))
attrs |= ATTR_RO;
return attrs;
static inline void fat_save_attrs(struct inode *inode, u8 attrs)
MSDOS_I(inode)->i_attrs = attrs & ATTR_UNUSED;
if (fat_mode_can_hold_ro(inode))
MSDOS_I(inode)->i_attrs = attrs & ATTR_UNUSED;
MSDOS_I(inode)->i_attrs = attrs & (ATTR_UNUSED | ATTR_RO);
static inline unsigned char fat_checksum(const __u8 *name)
......@@ -27,7 +27,12 @@ int fat_generic_ioctl(struct inode *inode, struct file *filp,
switch (cmd) {
u32 attr = fat_make_attrs(inode);
u32 attr;
attr = fat_make_attrs(inode);
return put_user(attr, user_attr);
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