[PATCH 4.9 002/101] ntfs: fix use-after-free in ntfs_ucsncmp()

From: Greg Kroah-Hartman
Date: Tue Aug 23 2022 - 04:12:25 EST

From: ChenXiaoSong <chenxiaosong2@xxxxxxxxxx>

commit 38c9c22a85aeed28d0831f230136e9cf6fa2ed44 upstream.

Syzkaller reported use-after-free bug as follows:

==================================================================
BUG: KASAN: use-after-free in ntfs_ucsncmp+0x123/0x130
Read of size 2 at addr ffff8880751acee8 by task a.out/879

CPU: 7 PID: 879 Comm: a.out Not tainted 5.19.0-rc4-next-20220630-00001-gcc5218c8bd2c-dirty #7
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0x1c0/0x2b0
print_address_description.constprop.0.cold+0xd4/0x484
print_report.cold+0x55/0x232
kasan_report+0xbf/0xf0
ntfs_ucsncmp+0x123/0x130
ntfs_are_names_equal.cold+0x2b/0x41
ntfs_attr_find+0x43b/0xb90
ntfs_attr_lookup+0x16d/0x1e0
ntfs_read_locked_attr_inode+0x4aa/0x2360
ntfs_attr_iget+0x1af/0x220
ntfs_read_locked_inode+0x246c/0x5120
ntfs_iget+0x132/0x180
load_system_files+0x1cc6/0x3480
ntfs_fill_super+0xa66/0x1cf0
mount_bdev+0x38d/0x460
legacy_get_tree+0x10d/0x220
vfs_get_tree+0x93/0x300
do_new_mount+0x2da/0x6d0
path_mount+0x496/0x19d0
__x64_sys_mount+0x284/0x300
do_syscall_64+0x3b/0xc0
entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f3f2118d9ea
Code: 48 8b 0d a9 f4 0b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 76 f4 0b 00 f7 d8 64 89 01 48
RSP: 002b:00007ffc269deac8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f3f2118d9ea
RDX: 0000000020000000 RSI: 0000000020000100 RDI: 00007ffc269dec00
RBP: 00007ffc269dec80 R08: 00007ffc269deb00 R09: 00007ffc269dec44
R10: 0000000000000000 R11: 0000000000000202 R12: 000055f81ab1d220
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>

The buggy address belongs to the physical page:
page:0000000085430378 refcount:1 mapcount:1 mapping:0000000000000000 index:0x555c6a81d pfn:0x751ac
memcg:ffff888101f7e180
anon flags: 0xfffffc00a0014(uptodate|lru|mappedtodisk|swapbacked|node=0|zone=1|lastcpupid=0x1fffff)
raw: 000fffffc00a0014 ffffea0001bf2988 ffffea0001de2448 ffff88801712e201
raw: 0000000555c6a81d 0000000000000000 0000000100000000 ffff888101f7e180
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880751acd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880751ace00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880751ace80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
^
ffff8880751acf00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8880751acf80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================

The reason is that struct ATTR_RECORD->name_offset is 6485, end address of
name string is out of bounds.

Fix this by adding sanity check on end address of attribute name string.

[akpm@xxxxxxxxxxxxxxxxxxxx: coding-style cleanups]
[chenxiaosong2@xxxxxxxxxx: cleanup suggested by Hawkins Jiawei]
Link: https://lkml.kernel.org/r/20220709064511.3304299-1-chenxiaosong2@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20220707105329.4020708-1-chenxiaosong2@xxxxxxxxxx
Signed-off-by: ChenXiaoSong <chenxiaosong2@xxxxxxxxxx>
Signed-off-by: Hawkins Jiawei <yin31149@xxxxxxxxx>
Cc: Anton Altaparmakov <anton@xxxxxxxxxx>
Cc: ChenXiaoSong <chenxiaosong2@xxxxxxxxxx>
Cc: Yongqiang Liu <liuyongqiang13@xxxxxxxxxx>
Cc: Zhang Yi <yi.zhang@xxxxxxxxxx>
Cc: Zhang Xiaoxu <zhangxiaoxu5@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/ntfs/attrib.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

--- a/fs/ntfs/attrib.c
+++ b/fs/ntfs/attrib.c
@@ -606,8 +606,12 @@ static int ntfs_attr_find(const ATTR_TYP
a = (ATTR_RECORD*)((u8*)ctx->attr +
le32_to_cpu(ctx->attr->length));
for (;; a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))) {
- if ((u8*)a < (u8*)ctx->mrec || (u8*)a > (u8*)ctx->mrec +
- le32_to_cpu(ctx->mrec->bytes_allocated))
+ u8 *mrec_end = (u8 *)ctx->mrec +
+ le32_to_cpu(ctx->mrec->bytes_allocated);
+ u8 *name_end = (u8 *)a + le16_to_cpu(a->name_offset) +
+ a->name_length * sizeof(ntfschar);
+ if ((u8*)a < (u8*)ctx->mrec || (u8*)a > mrec_end ||
+ name_end > mrec_end)
break;
ctx->attr = a;
if (unlikely(le32_to_cpu(a->type) > le32_to_cpu(type) ||