From 0e07362e1ad97d03cea758a51b86669b9b98b7d7 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Mon, 14 May 2018 07:41:00 +0200 Subject: [PATCH] ext4: fail ext4_iget for root directory if unallocated CVE-2018-1092 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 Signed-off-by: Theodore Ts'o Cc: stable@vger.kernel.org (cherry-picked from 8e4b5eae5decd9dfe5a4ee369c22028f90ab4c44) Signed-off-by: Khalid Elmously Acked-by: Andy Whitcroft Acked-by: Kleber Sacilotto de Souza Signed-off-by: Kleber Sacilotto de Souza --- fs/ext4/inode.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index e4159059a34d..566ccbb1e871 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4680,6 +4680,12 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino) 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 = -EFSCORRUPTED; + 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 > -- 2.39.2