On 2022/11/29 3:29, Viacheslav Dubeyko wrote:
On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@xxxxxxxxxx> wrote:
From: ZhangPeng <zhangpeng362@xxxxxxxxxx>
Syzbot reported a OOB Write bug:
loop0: detected capacity change from 0 to 64
==================================================================
BUG: KASAN: slab-out-of-bounds in hfs_asc2mac+0x467/0x9a0
fs/hfs/trans.c:133
Write of size 1 at addr ffff88801848314e by task syz-executor391/3632
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1b1/0x28e lib/dump_stack.c:106
print_address_description+0x74/0x340 mm/kasan/report.c:284
print_report+0x107/0x1f0 mm/kasan/report.c:395
kasan_report+0xcd/0x100 mm/kasan/report.c:495
hfs_asc2mac+0x467/0x9a0 fs/hfs/trans.c:133
hfs_cat_build_key+0x92/0x170 fs/hfs/catalog.c:28
hfs_lookup+0x1ab/0x2c0 fs/hfs/dir.c:31
lookup_open fs/namei.c:3391 [inline]
open_last_lookups fs/namei.c:3481 [inline]
path_openat+0x10e6/0x2df0 fs/namei.c:3710
do_filp_open+0x264/0x4f0 fs/namei.c:3740
If in->len is much larger than HFS_NAMELEN(31) which is the maximum
length of an HFS filename, a OOB Write could occur in hfs_asc2mac(). In
that case, when the dst reaches the boundary, the srclen is still
greater than 0, which causes a OOB Write.
Fix this by adding a Check on dstlen before Writing to dst address.
Fixes: 328b92278650 ("[PATCH] hfs: NLS support")
Reported-by: syzbot+dc3b1cf9111ab5fe98e7@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: ZhangPeng <zhangpeng362@xxxxxxxxxx>
---
fs/hfs/trans.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/hfs/trans.c b/fs/hfs/trans.c
index 39f5e343bf4d..886158db07b3 100644
--- a/fs/hfs/trans.c
+++ b/fs/hfs/trans.c
@@ -130,6 +130,8 @@ void hfs_asc2mac(struct super_block *sb, struct hfs_name *out, const struct qstr
dst += size;
dstlen -= size;
} else {
+ if (dstlen == 0)
+ goto out;
Maybe, it makes sense to use dstlen instead of srclen in while()?
We have now:
while (srclen > 0) {
<skipped>
} else {
<skipped>
}
We can use instead:
while (dstlen > 0) {
<skipped>
} else {
<skipped>
}
Will it fix the issue?
Thanks,
Slava.
Thank you for your help.
After testing, it fix the issue.
Would it be better to add dstlen > 0 instead of replacing srclen > 0 with dstlen > 0?
Because there may be dstlen > 0 and srclen <= 0.
we can use:
while (srclen > 0 && dstlen > 0) {
<skipped>
} else {
<skipped>
}
Thanks,
Zhang Peng
*dst++ = ch > 0xff ? '?' : ch;
dstlen--;
}
--
2.25.1
