From: "Luís Henriques" <lhenriques@suse.de>
To: "Theodore Ts'o" <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>
Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
"Luís Henriques" <lhenriques@suse.de>,
stable@vger.kernel.org
Subject: [PATCH v2] ext4: fix BUG_ON() when directory entry has invalid rec_len
Date: Wed, 12 Oct 2022 14:13:30 +0100 [thread overview]
Message-ID: <20221012131330.32456-1-lhenriques@suse.de> (raw)
In-Reply-To: <20221010142035.2051-1-lhenriques@suse.de>
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: stable@vger.kernel.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216540
Signed-off-by: Luís Henriques <lhenriques@suse.de>
---
* 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);
next prev parent reply other threads:[~2022-10-12 13:13 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-10 14:20 [PATCH] ext4: fix a NULL pointer when validating an inode bitmap Luís Henriques
2022-10-11 15:56 ` [PATCH v2] " Luís Henriques
2022-11-06 0:32 ` Theodore Ts'o
2022-11-08 14:06 ` Luís Henriques
2022-11-28 22:28 ` Theodore Ts'o
2022-11-29 3:18 ` Baokun Li
2022-11-29 21:00 ` Theodore Ts'o
2022-11-30 3:20 ` Baokun Li
2022-12-01 4:32 ` Theodore Ts'o
2022-12-01 6:20 ` Baokun Li
2022-10-12 13:13 ` Luís Henriques [this message]
2022-10-12 13:16 ` [PATCH v2] ext4: fix BUG_ON() when directory entry has invalid rec_len Luís Henriques
2022-10-12 14:21 ` Theodore Ts'o
2022-10-12 15:18 ` Luís Henriques
2022-11-06 6:16 ` Theodore Ts'o
2022-10-12 13:16 Luís Henriques
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