Corrupted ext4_dir_entry_2 struct on disk may have wrong inode number,
when the inode number is 8 (EXT4_JOURNAL_INO) and the file is deleted,
the journal inode is gone, and unmounting such a fs could trigger the
following BUG_ON() in start_this_handle().
BUG_ON(journal->j_flags & JBD2_UNMOUNT);
------------[ cut here ]------------
kernel BUG at fs/jbd2/transaction.c:307!
...
CPU: 1 PID: 1535 Comm: umount Not tainted 3.13.0+ #14
...
Call Trace:
[<ffffffff8119f17a>] ? kmem_cache_alloc+0x1ca/0x1f0
[<ffffffff812850f0>] ? jbd2__journal_start+0x90/0x1e0
[<ffffffff81285153>] jbd2__journal_start+0xf3/0x1e0
[<ffffffff81242a62>] ? ext4_evict_inode+0x1b2/0x4f0
[<ffffffff8126d039>] __ext4_journal_start_sb+0x69/0xe0
[<ffffffff81242a62>] ext4_evict_inode+0x1b2/0x4f0
[<ffffffff811d3b8e>] evict+0x9e/0x190
[<ffffffff811d4373>] iput+0xf3/0x180
[<ffffffff8128f301>] jbd2_journal_destroy+0x191/0x220
[<ffffffff810b0ae0>] ? abort_exclusive_wait+0xb0/0xb0
[<ffffffff8125d004>] ext4_put_super+0x64/0x340
[<ffffffff811bbae2>] generic_shutdown_super+0x72/0xf0
[<ffffffff811bbd77>] kill_block_super+0x27/0x70
[<ffffffff811bc05d>] deactivate_locked_super+0x3d/0x60
[<ffffffff811bc606>] deactivate_super+0x46/0x60
[<ffffffff811d7f47>] mntput_no_expire+0xa7/0x140
[<ffffffff811d939e>] SyS_umount+0x8e/0x100
[<ffffffff81690c29>] system_call_fastpath+0x16/0x1b
Check inode number in ext4_unlink() and return error if the inode number
is reserved or nonexistent(except EXT4_ROOT_INO, as Ted pointed out that
it's a security hole).
Tested by removing a reserved inode(modify the ondisk structure by hand)
and unmounting the fs. Inodes 1-10 have been tested. Also tested by
xfstests.
Signed-off-by: Eryu Guan <guaneryu@xxxxxxxxx>
---
(This is a v2 of an old patch, I forgot about the patch..)
v2: exempt the root inode as Ted suggested, although unlink("/") would be
catched by vfs and unlink a corrupt file with root inode number would be
catched by ext4_lookup, and won't reach ext4_unlink() in both cases
EXT4-fs error (device loop0): ext4_lookup:1441: inode #2: comm rm: 'testfile' linked to parent dir
Aborting journal on device loop0-8.
EXT4-fs (loop0): Remounting filesystem read-only
EXT4-fs error (device loop0): ext4_lookup:1441: inode #2: comm rm: 'testfile' linked to parent dir
fs/ext4/namei.c | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 603e4eb..6e6b312 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2796,9 +2796,11 @@ end_rmdir:
static int ext4_unlink(struct inode *dir, struct dentry *dentry)
{
int retval;
+ unsigned long ino;
struct inode *inode;
struct buffer_head *bh;
struct ext4_dir_entry_2 *de;
+ struct super_block *sb;
handle_t *handle = NULL;
trace_ext4_unlink_enter(dir, dentry);
@@ -2815,13 +2817,20 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
goto end_unlink;
inode = dentry->d_inode;
+ ino = inode->i_ino;
+ sb = dir->i_sb;
retval = -EIO;
- if (le32_to_cpu(de->inode) != inode->i_ino)
+ if (le32_to_cpu(de->inode) != ino)
goto end_unlink;
+ if ((ino < EXT4_FIRST_INO(sb) && ino != EXT4_ROOT_INO) ||
+ ino > le32_to_cpu(EXT4_SB(sb)->s_es->s_inodes_count)) {
+ ext4_error(sb, "reserved or nonexistent inode %lu", ino);
+ goto end_unlink;
+ }
handle = ext4_journal_start(dir, EXT4_HT_DIR,
- EXT4_DATA_TRANS_BLOCKS(dir->i_sb));
+ EXT4_DATA_TRANS_BLOCKS(sb));
if (IS_ERR(handle)) {
retval = PTR_ERR(handle);
handle = NULL;
--
1.8.3.1
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