[PATCH] hfs: Fix OOB Write in hfs_asc2mac

[PATCH] hfs: Fix OOB Write in hfs_asc2mac

[Peng Zhang]

From: ZhangPeng <zhangpeng362@huawei.com>

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@syzkaller.appspotmail.com
Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
---
 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;
 				*dst++ = ch > 0xff ? '?' : ch;
 				dstlen--;
 			}
-- 
2.25.1

Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac

[Viacheslav Dubeyko]

> On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@huawei.com> wrote:
> 
> From: ZhangPeng <zhangpeng362@huawei.com>
> 
> 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@syzkaller.appspotmail.com
> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
> ---
> 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.


> 				*dst++ = ch > 0xff ? '?' : ch;
> 				dstlen--;
> 			}
> -- 
> 2.25.1
> 

Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac

[zhangpeng (AS)]

On 2022/11/29 3:29, Viacheslav Dubeyko wrote:

>> On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@huawei.com> wrote:
>>
>> From: ZhangPeng <zhangpeng362@huawei.com>
>>
>> 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@syzkaller.appspotmail.com
>> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
>> ---
>> 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
>>
>

Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac

[Viacheslav Dubeyko]

> On Nov 28, 2022, at 6:23 PM, zhangpeng (AS) <zhangpeng362@huawei.com> wrote:
> 
> On 2022/11/29 3:29, Viacheslav Dubeyko wrote:
> 
>>> On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@huawei.com> wrote:
>>> 
>>> From: ZhangPeng <zhangpeng362@huawei.com>
>>> 
>>> 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@syzkaller.appspotmail.com
>>> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
>>> ---
>>> 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>
> }
> 

Looks good to me.

Thanks,
Slava.

> 
> Thanks,
> Zhang Peng
> 
>>> 				*dst++ = ch > 0xff ? '?' : ch;
>>> 				dstlen--;
>>> 			}
>>> -- 
>>> 2.25.1

Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac

[zhangpeng (AS)]

On 2022/11/30 3:08, Viacheslav Dubeyko wrote:
>> On Nov 28, 2022, at 6:23 PM, zhangpeng (AS) <zhangpeng362@huawei.com> wrote:
>>
>> On 2022/11/29 3:29, Viacheslav Dubeyko wrote:
>>>> On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@huawei.com> wrote:
>>>>
>>>> From: ZhangPeng <zhangpeng362@huawei.com>
>>>>
>>>> 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@syzkaller.appspotmail.com
>>>> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
>>>> ---
>>>> 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>
>> }
>>
> Looks good to me.

Can I put you down as a Reviewed-by or Suggested-by?

Thanks,
Zhang Peng

> Thanks,
> Slava.
>
>> Thanks,
>> Zhang Peng
>>
>>>> 				*dst++ = ch > 0xff ? '?' : ch;
>>>> 				dstlen--;
>>>> 			}
>>>> -- 
>>>> 2.25.1

Re: [PATCH] hfs: Fix OOB Write in hfs_asc2mac

[Viacheslav Dubeyko]

> On Nov 30, 2022, at 5:53 PM, zhangpeng (AS) <zhangpeng362@huawei.com> wrote:
> 
> 
> On 2022/11/30 3:08, Viacheslav Dubeyko wrote:
>>> On Nov 28, 2022, at 6:23 PM, zhangpeng (AS) <zhangpeng362@huawei.com> wrote:
>>> 
>>> On 2022/11/29 3:29, Viacheslav Dubeyko wrote:
>>>>> On Nov 25, 2022, at 8:36 PM, Peng Zhang <zhangpeng362@huawei.com> wrote:
>>>>> 
>>>>> From: ZhangPeng <zhangpeng362@huawei.com>
>>>>> 
>>>>> 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@syzkaller.appspotmail.com
>>>>> Signed-off-by: ZhangPeng <zhangpeng362@huawei.com>
>>>>> ---
>>>>> 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>
>>> }
>>> 
>> Looks good to me.
> 
> Can I put you down as a Reviewed-by or Suggested-by?

Sure. I hope to see the second version of the patch.

Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>

Thanks,
Slava.

> 
> Thanks,
> Zhang Peng
> 
>> Thanks,
>> Slava.
>> 
>>> Thanks,
>>> Zhang Peng
>>> 
>>>>> 				*dst++ = ch > 0xff ? '?' : ch;
>>>>> 				dstlen--;
>>>>> 			}
>>>>> -- 
>>>>> 2.25.1