1 ext4: fail ext4_iget for root directory if unallocated
3 If the root directory has an i_links_count of zero, then when the file
4 system is mounted, then when ext4_fill_super() notices the problem and
5 tries to call iput() the root directory in the error return path,
6 ext4_evict_inode() will try to free the inode on disk, before all of
7 the file system structures are set up, and this will result in an OOPS
8 caused by a NULL pointer dereference.
10 This issue has been assigned CVE-2018-1092.
12 https://bugzilla.kernel.org/show_bug.cgi?id=199179
13 https://bugzilla.redhat.com/show_bug.cgi?id=1560777
15 Reported-by: Wen Xu <wen.xu@gatech.edu>
16 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
17 Cc: stable@vger.kernel.org
19 fs/ext4/inode.c | 6 ++++++
20 1 file changed, 6 insertions(+)
22 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
23 index 435965598cb8..18aa2ef963ad 100644
26 @@ -4732,6 +4732,12 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
28 raw_inode = ext4_raw_inode(&iloc);
30 + if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) {
31 + EXT4_ERROR_INODE(inode, "root inode unallocated");
32 + ret = -EFSCORRUPTED;
36 if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
37 ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
38 if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >