Commit a3082d52 authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Linus Torvalds

fat: add simple validation for directory inode

This detects simple corruption cases of directory, and tries to avoid
further damage to user data.

And performance impact of this validation should be very low, or not
measurable.
Signed-off-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Reported-by: default avatarVegard Nossum <vegard.nossum@oracle.com>
Tested-by: default avatarVegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent a513d869
......@@ -449,6 +449,24 @@ static int fat_calc_dir_size(struct inode *inode)
return 0;
}
static int fat_validate_dir(struct inode *dir)
{
struct super_block *sb = dir->i_sb;
if (dir->i_nlink < 2) {
/* Directory should have "."/".." entries at least. */
fat_fs_error(sb, "corrupted directory (invalid entries)");
return -EIO;
}
if (MSDOS_I(dir)->i_start == 0 ||
MSDOS_I(dir)->i_start == MSDOS_SB(sb)->root_cluster) {
/* Directory should point valid cluster. */
fat_fs_error(sb, "corrupted directory (invalid i_start)");
return -EIO;
}
return 0;
}
/* doesn't deal with root inode */
int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
{
......@@ -475,6 +493,10 @@ int fat_fill_inode(struct inode *inode, struct msdos_dir_entry *de)
MSDOS_I(inode)->mmu_private = inode->i_size;
set_nlink(inode, fat_subdirs(inode));
error = fat_validate_dir(inode);
if (error < 0)
return error;
} else { /* not a directory */
inode->i_generation |= 1;
inode->i_mode = fat_make_mode(sbi, de->attr,
......
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