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authorOGAWA Hirofumi <[email protected]>2016-01-20 14:59:38 -0800
committerLinus Torvalds <[email protected]>2016-01-20 17:09:18 -0800
commita3082d526f2d406d4b488e49a508a0062a23314f (patch)
tree5d4b38520c00134925329278b127ae75ff45e902
parenta513d86983164a1f74a226ab7006deffbf63907e (diff)
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: OGAWA Hirofumi <[email protected]> Reported-by: Vegard Nossum <[email protected]> Tested-by: Vegard Nossum <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
-rw-r--r--fs/fat/inode.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 3ac9078fde65..08ef5fd0d502 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -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,