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authorTheodore Ts'o <tytso@mit.edu>2018-03-29 21:56:09 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-04-24 09:32:07 +0200
commit990251318b97ed7153d9adbf633035536c7d685b (patch)
tree021598fded0fd73c50e9de7c2ddf098a1e01da5a /fs
parent51e3b81b386104e1e088dd3abfb3d0c2a93d7631 (diff)
ext4: fail ext4_iget for root directory if unallocated
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 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext4/inode.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f0cabc8c96cb..6e8dbc1e4f95 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4231,6 +4231,12 @@ 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 >