This is a note to let you know that I've just added the patch titled
ext4: avoid a potential slab-out-of-bounds in ext4_group_desc_csum
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
ext4-avoid-a-potential-slab-out-of-bounds-in-ext4_group_desc_csum.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4f04351888a83e595571de672e0a4a8b74f4fb31 Mon Sep 17 00:00:00 2001
From: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
Date: Thu, 4 May 2023 12:15:25 +0000
Subject: ext4: avoid a potential slab-out-of-bounds in ext4_group_desc_csum
From: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
commit 4f04351888a83e595571de672e0a4a8b74f4fb31 upstream.
When modifying the block device while it is mounted by the filesystem,
syzbot reported the following:
BUG: KASAN: slab-out-of-bounds in crc16+0x206/0x280 lib/crc16.c:58
Read of size 1 at addr ffff888075f5c0a8 by task syz-executor.2/15586
CPU: 1 PID: 15586 Comm: syz-executor.2 Not tainted 6.2.0-rc5-syzkaller-00205-gc96618275234 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/12/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x290 lib/dump_stack.c:106
print_address_description+0x74/0x340 mm/kasan/report.c:306
print_report+0x107/0x1f0 mm/kasan/report.c:417
kasan_report+0xcd/0x100 mm/kasan/report.c:517
crc16+0x206/0x280 lib/crc16.c:58
ext4_group_desc_csum+0x81b/0xb20 fs/ext4/super.c:3187
ext4_group_desc_csum_set+0x195/0x230 fs/ext4/super.c:3210
ext4_mb_clear_bb fs/ext4/mballoc.c:6027 [inline]
ext4_free_blocks+0x191a/0x2810 fs/ext4/mballoc.c:6173
ext4_remove_blocks fs/ext4/extents.c:2527 [inline]
ext4_ext_rm_leaf fs/ext4/extents.c:2710 [inline]
ext4_ext_remove_space+0x24ef/0x46a0 fs/ext4/extents.c:2958
ext4_ext_truncate+0x177/0x220 fs/ext4/extents.c:4416
ext4_truncate+0xa6a/0xea0 fs/ext4/inode.c:4342
ext4_setattr+0x10c8/0x1930 fs/ext4/inode.c:5622
notify_change+0xe50/0x1100 fs/attr.c:482
do_truncate+0x200/0x2f0 fs/open.c:65
handle_truncate fs/namei.c:3216 [inline]
do_open fs/namei.c:3561 [inline]
path_openat+0x272b/0x2dd0 fs/namei.c:3714
do_filp_open+0x264/0x4f0 fs/namei.c:3741
do_sys_openat2+0x124/0x4e0 fs/open.c:1310
do_sys_open fs/open.c:1326 [inline]
__do_sys_creat fs/open.c:1402 [inline]
__se_sys_creat fs/open.c:1396 [inline]
__x64_sys_creat+0x11f/0x160 fs/open.c:1396
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f72f8a8c0c9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f72f97e3168 EFLAGS: 00000246 ORIG_RAX: 0000000000000055
RAX: ffffffffffffffda RBX: 00007f72f8bac050 RCX: 00007f72f8a8c0c9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000280
RBP: 00007f72f8ae7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd165348bf R14: 00007f72f97e3300 R15: 0000000000022000
Replace
le16_to_cpu(sbi->s_es->s_desc_size)
with
sbi->s_desc_size
It reduces ext4's compiled text size, and makes the code more efficient
(we remove an extra indirect reference and a potential byte
swap on big endian systems), and there is no downside. It also avoids the
potential KASAN / syzkaller failure, as a bonus.
Reported-by: syzbot+fc51227e7100c9294894@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+8785e41224a3afd04321@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://syzkaller.appspot.com/bug?id=70d28d11ab14bd7938f3e088365252aa923cff42
Link: https://syzkaller.appspot.com/bug?id=b85721b38583ecc6b5e72ff524c67302abbc30f3
Link: https://lore.kernel.org/all/000000000000ece18705f3b20934@xxxxxxxxxx/
Fixes: 717d50e4971b ("Ext4: Uninitialized Block Groups")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tudor Ambarus <tudor.ambarus@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230504121525.3275886-1-tudor.ambarus@xxxxxxxxxx
Signed-off-by: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ext4/super.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2475,11 +2475,9 @@ static __le16 ext4_group_desc_csum(struc
crc = crc16(crc, (__u8 *)gdp, offset);
offset += sizeof(gdp->bg_checksum); /* skip checksum */
/* for checksum of struct ext4_group_desc do the rest...*/
- if (ext4_has_feature_64bit(sb) &&
- offset < le16_to_cpu(sbi->s_es->s_desc_size))
+ if (ext4_has_feature_64bit(sb) && offset < sbi->s_desc_size)
crc = crc16(crc, (__u8 *)gdp + offset,
- le16_to_cpu(sbi->s_es->s_desc_size) -
- offset);
+ sbi->s_desc_size - offset);
out:
return cpu_to_le16(crc);
Patches currently in stable-queue which might be from tudor.ambarus@xxxxxxxxxx are
queue-5.4/ext4-fix-use-after-free-read-in-ext4_find_extent-for.patch
queue-5.4/ext4-avoid-a-potential-slab-out-of-bounds-in-ext4_group_desc_csum.patch
