| From 8e4b5eae5decd9dfe5a4ee369c22028f90ab4c44 Mon Sep 17 00:00:00 2001 |
| From: Theodore Ts'o <tytso@mit.edu> |
| Date: Thu, 29 Mar 2018 21:56:09 -0400 |
| Subject: ext4: fail ext4_iget for root directory if unallocated |
| |
| From: Theodore Ts'o <tytso@mit.edu> |
| |
| commit 8e4b5eae5decd9dfe5a4ee369c22028f90ab4c44 upstream. |
| |
| If the root directory has an i_links_count of zero, then when the file |
| system is mounted, then when ext4_fill_super() notices the problem and |
| tries to call iput() the root directory in the error return path, |
| ext4_evict_inode() will try to free the inode on disk, before all of |
| the file system structures are set up, and this will result in an OOPS |
| caused by a NULL pointer dereference. |
| |
| This issue has been assigned CVE-2018-1092. |
| |
| https://bugzilla.kernel.org/show_bug.cgi?id=199179 |
| https://bugzilla.redhat.com/show_bug.cgi?id=1560777 |
| |
| Reported-by: Wen Xu <wen.xu@gatech.edu> |
| Signed-off-by: Theodore Ts'o <tytso@mit.edu> |
| Cc: stable@vger.kernel.org |
| [harsh@prjkt.io: s/EFSCORRUPTED/EUCLEAN/ fs/ext4/inode.c] |
| Signed-off-by: Harsh Shandilya <harsh@prjkt.io> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| fs/ext4/inode.c | 6 ++++++ |
| 1 file changed, 6 insertions(+) |
| |
| --- a/fs/ext4/inode.c |
| +++ b/fs/ext4/inode.c |
| @@ -3975,6 +3975,12 @@ struct inode *ext4_iget(struct super_blo |
| goto bad_inode; |
| raw_inode = ext4_raw_inode(&iloc); |
| |
| + if ((ino == EXT4_ROOT_INO) && (raw_inode->i_links_count == 0)) { |
| + EXT4_ERROR_INODE(inode, "root inode unallocated"); |
| + ret = -EUCLEAN; |
| + goto bad_inode; |
| + } |
| + |
| if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) { |
| ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize); |
| if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize > |
