The rec_len field in the directory entry has to be a multiple of 4. A
corrupted filesystem image can be used to hit a BUG() in
ext4_rec_len_to_disk(), called from make_indexed_dir().
------------[ cut here ]------------
kernel BUG at fs/ext4/ext4.h:2413!
...
RIP: 0010:make_indexed_dir+0x53f/0x5f0
...
Call Trace:
<TASK>
? add_dirent_to_buf+0x1b2/0x200
ext4_add_entry+0x36e/0x480
ext4_add_nondir+0x2b/0xc0
ext4_create+0x163/0x200
path_openat+0x635/0xe90
do_filp_open+0xb4/0x160
? __create_object.isra.0+0x1de/0x3b0
? _raw_spin_unlock+0x12/0x30
do_sys_openat2+0x91/0x150
__x64_sys_open+0x6c/0xa0
do_syscall_64+0x3c/0x80
entry_SYSCALL_64_after_hwframe+0x46/0xb0
The fix simply adds a call to ext4_check_dir_entry() to validate the
directory entry, returning -EFSCORRUPTED if the entry is invalid.
CC: [email protected]
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216540
Signed-off-by: Luís Henriques <[email protected]>
---
* Changes since v1:
As suggested by Ted, I've removed the incorrect 'de->rec_len' check from
previous version and replaced it with a call to ext4_check_dir_entry()
instead, which is a much more complete verification.
fs/ext4/namei.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 3a31b662f661..ed76e89ffbe9 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2254,8 +2254,16 @@ static int make_indexed_dir(handle_t *handle, struct ext4_filename *fname,
memset(de, 0, len); /* wipe old data */
de = (struct ext4_dir_entry_2 *) data2;
top = data2 + len;
- while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top)
+ while ((char *)(de2 = ext4_next_entry(de, blocksize)) < top) {
+ if (ext4_check_dir_entry(dir, NULL, de, bh2, data2, len,
+ (data2 + (blocksize - csum_size) -
+ (char *) de))) {
+ brelse(bh2);
+ brelse(bh);
+ return -EFSCORRUPTED;
+ }
de = de2;
+ }
de->rec_len = ext4_rec_len_to_disk(data2 + (blocksize - csum_size) -
(char *) de, blocksize);
On Wed, Oct 12, 2022 at 10:21:39AM -0400, Theodore Ts'o wrote:
> On Wed, Oct 12, 2022 at 02:16:42PM +0100, Lu?s Henriques wrote:
> > Grr, looks like I accidentally reused a 'git send-email' from shell
> > history which had a '--in-reply-to' in it. Please ignore and sorry about
> > that. I've just resent a new email.
>
> No worries! The --in-reply-to wasn't actually a problem, since b4
> generally will do the right thing (and sometimes humans prefer the
> in-reply-to since they can more easily see the patch that it is
> replacing/obsoleting).
>
> b4 can sometimes get confused when a patch series gets split, and both
> parts of the patch series are in a reply-to mail thread to the
> original patch series, since if it can't use the -vn+1 hueristic or
> the "subject line has stayed the same but has a newer date" hueristic,
> it falls back to "latest patch in the mail thread". So if there are
> two "valid" patches or patch series in an e-mail thread, b4 -c
> (--check-newer-revisions) can get confused. But even in that case,
> that it's more a minor annoyance than anything else.
>
> So in the future, don't feel that you need to resend a patch if
> there's an incorrect/older --in-reply-to; it's not a big deal.
Great, I haven't yet included b4 in my workflow so, to be honest, I didn't
really thought about that tool being confused. What really made me resend
the patch was that I used the *wrong message-ID in the "--in-reply-to"!
And that thread already had a v2 patch, which would could easily confuse
humans. Hopefully, b4 won't be confused by that either.
Cheers,
--
Lu?s