[v2] fs/ntfs: fix BUG_ON of ntfs_read_block()

[PATCH v2] fs/ntfs: fix BUG_ON of ntfs_read_block()

Posted by cgel.zte@gmail.com 3 years, 10 months ago

From: xu xin <xu.xin16@zte.com.cn>

As the bug description at
https://lore.kernel.org/lkml/20220623033635.973929-1-xu.xin16@zte.com.cn/
attckers can use this bug to crash the system.

So to avoid panic, remove the BUG_ON, and use ntfs_warning to output a
warning to the syslog and return instead until someone really solve
the problem.

Cc: stable@vger.kernel.org
Reported-by: Zeal Robot <zealci@zte.com.cn>
Reported-by: syzbot+6a5a7672f663cce8b156@syzkaller.appspotmail.com
Reviewed-by: Songyi Zhang <zhang.songyi@zte.com.cn>
Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Jiang Xuexin<jiang.xuexin@zte.com.cn>
Reviewed-by: Zhang wenya<zhang.wenya1@zte.com.cn>
Signed-off-by: xu xin <xu.xin16@zte.com.cn>
---

Change for v2:
 - Use ntfs_warning instead of WARN().
 - Add the tag Cc: stable@vger.kernel.org.
---
 fs/ntfs/aops.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index 5f4fb6ca6f2e..84d68efb4ace 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -183,7 +183,12 @@ static int ntfs_read_block(struct page *page)
 	vol = ni->vol;
 
 	/* $MFT/$DATA must have its complete runlist in memory at all times. */
-	BUG_ON(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni));
+	if (unlikely(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni))) {
+		ntfs_warning(vi->i_sb, "Error because ni->runlist.rl, ni->mft_no, "
+				"and NInoAttr(ni) is null.");
+		unlock_page(page);
+		return -EINVAL;
+	}
 
 	blocksize = vol->sb->s_blocksize;
 	blocksize_bits = vol->sb->s_blocksize_bits;
-- 
2.25.1

Re: [PATCH v2] fs/ntfs: fix BUG_ON of ntfs_read_block()

Posted by Eric Biggers 3 years, 10 months ago

On Thu, Jun 23, 2022 at 09:49:56AM +0000, cgel.zte@gmail.com wrote:
> From: xu xin <xu.xin16@zte.com.cn>
> 
> As the bug description at
> https://lore.kernel.org/lkml/20220623033635.973929-1-xu.xin16@zte.com.cn/
> attckers can use this bug to crash the system.
> 
> So to avoid panic, remove the BUG_ON, and use ntfs_warning to output a
> warning to the syslog and return instead until someone really solve
> the problem.
> 
> Cc: stable@vger.kernel.org
> Reported-by: Zeal Robot <zealci@zte.com.cn>
> Reported-by: syzbot+6a5a7672f663cce8b156@syzkaller.appspotmail.com
> Reviewed-by: Songyi Zhang <zhang.songyi@zte.com.cn>
> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
> Reviewed-by: Jiang Xuexin<jiang.xuexin@zte.com.cn>
> Reviewed-by: Zhang wenya<zhang.wenya1@zte.com.cn>
> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
> ---
> 
> Change for v2:
>  - Use ntfs_warning instead of WARN().
>  - Add the tag Cc: stable@vger.kernel.org.
> ---
>  fs/ntfs/aops.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
> index 5f4fb6ca6f2e..84d68efb4ace 100644
> --- a/fs/ntfs/aops.c
> +++ b/fs/ntfs/aops.c
> @@ -183,7 +183,12 @@ static int ntfs_read_block(struct page *page)
>  	vol = ni->vol;
>  
>  	/* $MFT/$DATA must have its complete runlist in memory at all times. */
> -	BUG_ON(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni));
> +	if (unlikely(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni))) {
> +		ntfs_warning(vi->i_sb, "Error because ni->runlist.rl, ni->mft_no, "
> +				"and NInoAttr(ni) is null.");
> +		unlock_page(page);
> +		return -EINVAL;
> +	}

A better warning message that doesn't rely on implementation details (struct
field and macro names) would be "Runlist of $MFT/$DATA is not cached".  Also,
why does this situation happen in the first place?  Is there a way to prevent
this situation in the first place?

- Eric

Re: [PATCH v2] fs/ntfs: fix BUG_ON of ntfs_read_block()

Posted by Namjae Jeon 3 years, 9 months ago

2022-06-24 2:08 GMT+09:00, Eric Biggers <ebiggers@kernel.org>:
> On Thu, Jun 23, 2022 at 09:49:56AM +0000, cgel.zte@gmail.com wrote:
>> From: xu xin <xu.xin16@zte.com.cn>
>>
>> As the bug description at
>> https://lore.kernel.org/lkml/20220623033635.973929-1-xu.xin16@zte.com.cn/
>> attckers can use this bug to crash the system.
>>
>> So to avoid panic, remove the BUG_ON, and use ntfs_warning to output a
>> warning to the syslog and return instead until someone really solve
>> the problem.
>>
>> Cc: stable@vger.kernel.org
>> Reported-by: Zeal Robot <zealci@zte.com.cn>
>> Reported-by: syzbot+6a5a7672f663cce8b156@syzkaller.appspotmail.com
>> Reviewed-by: Songyi Zhang <zhang.songyi@zte.com.cn>
>> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
>> Reviewed-by: Jiang Xuexin<jiang.xuexin@zte.com.cn>
>> Reviewed-by: Zhang wenya<zhang.wenya1@zte.com.cn>
>> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
>> ---
>>
>> Change for v2:
>>  - Use ntfs_warning instead of WARN().
>>  - Add the tag Cc: stable@vger.kernel.org.
>> ---
>>  fs/ntfs/aops.c | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
>> index 5f4fb6ca6f2e..84d68efb4ace 100644
>> --- a/fs/ntfs/aops.c
>> +++ b/fs/ntfs/aops.c
>> @@ -183,7 +183,12 @@ static int ntfs_read_block(struct page *page)
>>  	vol = ni->vol;
>>
>>  	/* $MFT/$DATA must have its complete runlist in memory at all times. */
>> -	BUG_ON(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni));
>> +	if (unlikely(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni))) {
>> +		ntfs_warning(vi->i_sb, "Error because ni->runlist.rl, ni->mft_no, "
>> +				"and NInoAttr(ni) is null.");
>> +		unlock_page(page);
>> +		return -EINVAL;
>> +	}
>
> A better warning message that doesn't rely on implementation details
> (struct
> field and macro names) would be "Runlist of $MFT/$DATA is not cached".
> Also,
> why does this situation happen in the first place?  Is there a way to
> prevent
> this situation in the first place?

ntfs_mapping_pairs_decompress() should return error pointer instead of NULL.
Callers is checking error value using IS_ERR(). and the mapping pairs
array of @MFT entry is empty, I think it's corrupted, it should cause
mount failure.

I haven't checked if this patch fix the problem. Xu, Can you check it ?

diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
index 97932fb5179c..31263fe0772f 100644
--- a/fs/ntfs/runlist.c
+++ b/fs/ntfs/runlist.c
@@ -766,8 +766,11 @@ runlist_element
*ntfs_mapping_pairs_decompress(const ntfs_volume *vol,
                return ERR_PTR(-EIO);
        }
        /* If the mapping pairs array is valid but empty, nothing to do. */
-       if (!vcn && !*buf)
+       if (!vcn && !*buf) {
+               if (!old_rl)
+                       return ERR_PTR(-EIO);
                return old_rl;
+       }
        /* Current position in runlist array. */
        rlpos = 0;
        /* Allocate first page and set current runlist size to one page. */

>
> - Eric
>

Re: [PATCH v2] fs/ntfs: fix BUG_ON of ntfs_read_block()

Posted by CGEL 3 years, 9 months ago

On Fri, Jun 24, 2022 at 11:33:28AM +0900, Namjae Jeon wrote:
> 2022-06-24 2:08 GMT+09:00, Eric Biggers <ebiggers@kernel.org>:
> > On Thu, Jun 23, 2022 at 09:49:56AM +0000, cgel.zte@gmail.com wrote:
> >> From: xu xin <xu.xin16@zte.com.cn>
> >>
> >> As the bug description at
> >> https://lore.kernel.org/lkml/20220623033635.973929-1-xu.xin16@zte.com.cn/
> >> attckers can use this bug to crash the system.
> >>
> >> So to avoid panic, remove the BUG_ON, and use ntfs_warning to output a
> >> warning to the syslog and return instead until someone really solve
> >> the problem.
> >>
> >> Cc: stable@vger.kernel.org
> >> Reported-by: Zeal Robot <zealci@zte.com.cn>
> >> Reported-by: syzbot+6a5a7672f663cce8b156@syzkaller.appspotmail.com
> >> Reviewed-by: Songyi Zhang <zhang.songyi@zte.com.cn>
> >> Reviewed-by: Yang Yang <yang.yang29@zte.com.cn>
> >> Reviewed-by: Jiang Xuexin<jiang.xuexin@zte.com.cn>
> >> Reviewed-by: Zhang wenya<zhang.wenya1@zte.com.cn>
> >> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
> >> ---
> >>
> >> Change for v2:
> >>  - Use ntfs_warning instead of WARN().
> >>  - Add the tag Cc: stable@vger.kernel.org.
> >> ---
> >>  fs/ntfs/aops.c | 7 ++++++-
> >>  1 file changed, 6 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
> >> index 5f4fb6ca6f2e..84d68efb4ace 100644
> >> --- a/fs/ntfs/aops.c
> >> +++ b/fs/ntfs/aops.c
> >> @@ -183,7 +183,12 @@ static int ntfs_read_block(struct page *page)
> >>  	vol = ni->vol;
> >>
> >>  	/* $MFT/$DATA must have its complete runlist in memory at all times. */
> >> -	BUG_ON(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni));
> >> +	if (unlikely(!ni->runlist.rl && !ni->mft_no && !NInoAttr(ni))) {
> >> +		ntfs_warning(vi->i_sb, "Error because ni->runlist.rl, ni->mft_no, "
> >> +				"and NInoAttr(ni) is null.");
> >> +		unlock_page(page);
> >> +		return -EINVAL;
> >> +	}
> >
> > A better warning message that doesn't rely on implementation details
> > (struct
> > field and macro names) would be "Runlist of $MFT/$DATA is not cached".
> > Also,
> > why does this situation happen in the first place?  Is there a way to
> > prevent
> > this situation in the first place?
> 
> ntfs_mapping_pairs_decompress() should return error pointer instead of NULL.
> Callers is checking error value using IS_ERR(). and the mapping pairs
> array of @MFT entry is empty, I think it's corrupted, it should cause
> mount failure.
> 
> I haven't checked if this patch fix the problem. Xu, Can you check it ?
> 

I have test it and it fixes the problem.

Thanks.

> diff --git a/fs/ntfs/runlist.c b/fs/ntfs/runlist.c
> index 97932fb5179c..31263fe0772f 100644
> --- a/fs/ntfs/runlist.c
> +++ b/fs/ntfs/runlist.c
> @@ -766,8 +766,11 @@ runlist_element
> *ntfs_mapping_pairs_decompress(const ntfs_volume *vol,
>                 return ERR_PTR(-EIO);
>         }
>         /* If the mapping pairs array is valid but empty, nothing to do. */
> -       if (!vcn && !*buf)
> +       if (!vcn && !*buf) {
> +               if (!old_rl)
> +                       return ERR_PTR(-EIO);
>                 return old_rl;
> +       }
>         /* Current position in runlist array. */
>         rlpos = 0;
>         /* Allocate first page and set current runlist size to one page. */
> 
> >
> > - Eric
> >