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[PATCH] bcachefs: Fix invalid shift in validate_sb_layout()

Gianfranco Trad posted 1 patch 1 month ago 
fs/bcachefs/errcode.h  | 1 +
fs/bcachefs/super-io.c | 5 +++++
2 files changed, 6 insertions(+)
[PATCH] bcachefs: Fix invalid shift in validate_sb_layout()
Posted by Gianfranco Trad 1 month ago 
Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
to prevent UBSAN shift-out-of-bounds in validate_sb_layout().

Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
Tested-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
---
 fs/bcachefs/errcode.h  | 1 +
 fs/bcachefs/super-io.c | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
index 649263516ab1..b6cbd716000b 100644
--- a/fs/bcachefs/errcode.h
+++ b/fs/bcachefs/errcode.h
@@ -222,6 +222,7 @@
 	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_type)			\
 	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_nr_superblocks)	\
 	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_superblocks_overlap)	\
+	x(BCH_ERR_invalid_sb_layout,    invalid_sb_layout_sb_max_size_bits)     \
 	x(BCH_ERR_invalid_sb,		invalid_sb_members_missing)		\
 	x(BCH_ERR_invalid_sb,		invalid_sb_members)			\
 	x(BCH_ERR_invalid_sb,		invalid_sb_disk_groups)			\
diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index ce7410d72089..44d0ac9b00dd 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -287,6 +287,11 @@ static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out
 		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
 	}
 
+	if (layout->sb_max_size_bits > BCH_SB_LAYOUT_SIZE_BITS_MAX) {
+		prt_printf(out, "Invalid superblock layout: max_size_bits too high");
+		return -BCH_ERR_invalid_sb_layout_sb_max_size_bits;
+	}
+
 	max_sectors = 1 << layout->sb_max_size_bits;
 
 	prev_offset = le64_to_cpu(layout->sb_offset[0]);
-- 
2.43.0
Re: [PATCH] bcachefs: Fix invalid shift in validate_sb_layout()
Posted by Kent Overstreet 1 month ago 
On Wed, Oct 23, 2024 at 11:30:44PM +0200, Gianfranco Trad wrote:
> Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
> to prevent UBSAN shift-out-of-bounds in validate_sb_layout().
> 
> Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
> Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
> Tested-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
> Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>

looks correct, applied

> ---
>  fs/bcachefs/errcode.h  | 1 +
>  fs/bcachefs/super-io.c | 5 +++++
>  2 files changed, 6 insertions(+)
> 
> diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
> index 649263516ab1..b6cbd716000b 100644
> --- a/fs/bcachefs/errcode.h
> +++ b/fs/bcachefs/errcode.h
> @@ -222,6 +222,7 @@
>  	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_type)			\
>  	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_nr_superblocks)	\
>  	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_superblocks_overlap)	\
> +	x(BCH_ERR_invalid_sb_layout,    invalid_sb_layout_sb_max_size_bits)     \
>  	x(BCH_ERR_invalid_sb,		invalid_sb_members_missing)		\
>  	x(BCH_ERR_invalid_sb,		invalid_sb_members)			\
>  	x(BCH_ERR_invalid_sb,		invalid_sb_disk_groups)			\
> diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
> index ce7410d72089..44d0ac9b00dd 100644
> --- a/fs/bcachefs/super-io.c
> +++ b/fs/bcachefs/super-io.c
> @@ -287,6 +287,11 @@ static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out
>  		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
>  	}
>  
> +	if (layout->sb_max_size_bits > BCH_SB_LAYOUT_SIZE_BITS_MAX) {
> +		prt_printf(out, "Invalid superblock layout: max_size_bits too high");
> +		return -BCH_ERR_invalid_sb_layout_sb_max_size_bits;
> +	}
> +
>  	max_sectors = 1 << layout->sb_max_size_bits;
>  
>  	prev_offset = le64_to_cpu(layout->sb_offset[0]);
> -- 
> 2.43.0
>
Re: [PATCH] bcachefs: Fix invalid shift in validate_sb_layout()
Posted by Gianfranco Trad 1 month ago 
On 23/10/24 23:30, Gianfranco Trad wrote:
> Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
> to prevent UBSAN shift-out-of-bounds in validate_sb_layout().
> 
> Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
> Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
> Tested-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
> Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
> ---
>   fs/bcachefs/errcode.h  | 1 +
>   fs/bcachefs/super-io.c | 5 +++++
>   2 files changed, 6 insertions(+)
> 
> diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
> index 649263516ab1..b6cbd716000b 100644
> --- a/fs/bcachefs/errcode.h
> +++ b/fs/bcachefs/errcode.h
> @@ -222,6 +222,7 @@
>   	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_type)			\
>   	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_nr_superblocks)	\
>   	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_superblocks_overlap)	\
> +	x(BCH_ERR_invalid_sb_layout,    invalid_sb_layout_sb_max_size_bits)     \
>   	x(BCH_ERR_invalid_sb,		invalid_sb_members_missing)		\
>   	x(BCH_ERR_invalid_sb,		invalid_sb_members)			\
>   	x(BCH_ERR_invalid_sb,		invalid_sb_disk_groups)			\
> diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
> index ce7410d72089..44d0ac9b00dd 100644
> --- a/fs/bcachefs/super-io.c
> +++ b/fs/bcachefs/super-io.c
> @@ -287,6 +287,11 @@ static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out
>   		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
>   	}
>   
> +	if (layout->sb_max_size_bits > BCH_SB_LAYOUT_SIZE_BITS_MAX) {
> +		prt_printf(out, "Invalid superblock layout: max_size_bits too high");
> +		return -BCH_ERR_invalid_sb_layout_sb_max_size_bits;
> +	}
> +
>   	max_sectors = 1 << layout->sb_max_size_bits;
>   
>   	prev_offset = le64_to_cpu(layout->sb_offset[0]);

Wondering if this other patch might be considered more correct to 
prevent shift oob, given also [0]:

diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
index ce7410d72089..428172897501 100644
--- a/fs/bcachefs/super-io.c
+++ b/fs/bcachefs/super-io.c
@@ -287,7 +287,7 @@ static int validate_sb_layout(struct bch_sb_layout 
*layout, struct printbuf *out
  		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
  	}

-	max_sectors = 1 << layout->sb_max_size_bits;
+	max_sectors = 1 << min(BCH_SB_LAYOUT_SIZE_BITS_MAX, 
layout->sb_max_size_bits);

  	prev_offset = le64_to_cpu(layout->sb_offset[0]);

Also this patch was already tested by syzbot [1]

[0] 71dac2482ad3c8d4a8b8998a96751f009bad895f ("bcachefs: 
BCH_SB_LAYOUT_SIZE_BITS_MAX")
[1] https://syzkaller.appspot.com/x/log.txt?x=1640b640580000

Thanks for your time,

-- Gian
Re: [PATCH] bcachefs: Fix invalid shift in validate_sb_layout()
Posted by Kent Overstreet 1 month ago 
On Thu, Oct 24, 2024 at 12:48:30PM +0200, Gianfranco Trad wrote:
> On 23/10/24 23:30, Gianfranco Trad wrote:
> > Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
> > to prevent UBSAN shift-out-of-bounds in validate_sb_layout().
> > 
> > Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
> > Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
> > Tested-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
> > Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
> > ---
> >   fs/bcachefs/errcode.h  | 1 +
> >   fs/bcachefs/super-io.c | 5 +++++
> >   2 files changed, 6 insertions(+)
> > 
> > diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
> > index 649263516ab1..b6cbd716000b 100644
> > --- a/fs/bcachefs/errcode.h
> > +++ b/fs/bcachefs/errcode.h
> > @@ -222,6 +222,7 @@
> >   	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_type)			\
> >   	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_nr_superblocks)	\
> >   	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_superblocks_overlap)	\
> > +	x(BCH_ERR_invalid_sb_layout,    invalid_sb_layout_sb_max_size_bits)     \
> >   	x(BCH_ERR_invalid_sb,		invalid_sb_members_missing)		\
> >   	x(BCH_ERR_invalid_sb,		invalid_sb_members)			\
> >   	x(BCH_ERR_invalid_sb,		invalid_sb_disk_groups)			\
> > diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
> > index ce7410d72089..44d0ac9b00dd 100644
> > --- a/fs/bcachefs/super-io.c
> > +++ b/fs/bcachefs/super-io.c
> > @@ -287,6 +287,11 @@ static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out
> >   		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
> >   	}
> > +	if (layout->sb_max_size_bits > BCH_SB_LAYOUT_SIZE_BITS_MAX) {
> > +		prt_printf(out, "Invalid superblock layout: max_size_bits too high");
> > +		return -BCH_ERR_invalid_sb_layout_sb_max_size_bits;
> > +	}
> > +
> >   	max_sectors = 1 << layout->sb_max_size_bits;
> >   	prev_offset = le64_to_cpu(layout->sb_offset[0]);
> 
> Wondering if this other patch might be considered more correct to prevent
> shift oob, given also [0]:

Your first patch looks better, we want to know if we're feeding it
garbage

> 
> diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
> index ce7410d72089..428172897501 100644
> --- a/fs/bcachefs/super-io.c
> +++ b/fs/bcachefs/super-io.c
> @@ -287,7 +287,7 @@ static int validate_sb_layout(struct bch_sb_layout
> *layout, struct printbuf *out
>  		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
>  	}
> 
> -	max_sectors = 1 << layout->sb_max_size_bits;
> +	max_sectors = 1 << min(BCH_SB_LAYOUT_SIZE_BITS_MAX,
> layout->sb_max_size_bits);
> 
>  	prev_offset = le64_to_cpu(layout->sb_offset[0]);
> 
> Also this patch was already tested by syzbot [1]
> 
> [0] 71dac2482ad3c8d4a8b8998a96751f009bad895f ("bcachefs:
> BCH_SB_LAYOUT_SIZE_BITS_MAX")
> [1] https://syzkaller.appspot.com/x/log.txt?x=1640b640580000
> 
> Thanks for your time,
> 
> -- Gian
> 
> 
> 
> 
>
Re: [PATCH] bcachefs: Fix invalid shift in validate_sb_layout()
Posted by Gianfranco Trad 1 month ago 
On 24/10/24 13:24, Kent Overstreet wrote:
> On Thu, Oct 24, 2024 at 12:48:30PM +0200, Gianfranco Trad wrote:
>> On 23/10/24 23:30, Gianfranco Trad wrote:
>>> Add check on layout->sb_max_size_bits against BCH_SB_LAYOUT_SIZE_BITS_MAX
>>> to prevent UBSAN shift-out-of-bounds in validate_sb_layout().
>>>
>>> Reported-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
>>> Closes: https://syzkaller.appspot.com/bug?extid=089fad5a3a5e77825426
>>> Fixes: 03ef80b469d5 ("bcachefs: Ignore unknown mount options")
>>> Tested-by: syzbot+089fad5a3a5e77825426@syzkaller.appspotmail.com
>>> Signed-off-by: Gianfranco Trad <gianf.trad@gmail.com>
>>> ---
>>>    fs/bcachefs/errcode.h  | 1 +
>>>    fs/bcachefs/super-io.c | 5 +++++
>>>    2 files changed, 6 insertions(+)
>>>
>>> diff --git a/fs/bcachefs/errcode.h b/fs/bcachefs/errcode.h
>>> index 649263516ab1..b6cbd716000b 100644
>>> --- a/fs/bcachefs/errcode.h
>>> +++ b/fs/bcachefs/errcode.h
>>> @@ -222,6 +222,7 @@
>>>    	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_type)			\
>>>    	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_nr_superblocks)	\
>>>    	x(BCH_ERR_invalid_sb_layout,	invalid_sb_layout_superblocks_overlap)	\
>>> +	x(BCH_ERR_invalid_sb_layout,    invalid_sb_layout_sb_max_size_bits)     \
>>>    	x(BCH_ERR_invalid_sb,		invalid_sb_members_missing)		\
>>>    	x(BCH_ERR_invalid_sb,		invalid_sb_members)			\
>>>    	x(BCH_ERR_invalid_sb,		invalid_sb_disk_groups)			\
>>> diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
>>> index ce7410d72089..44d0ac9b00dd 100644
>>> --- a/fs/bcachefs/super-io.c
>>> +++ b/fs/bcachefs/super-io.c
>>> @@ -287,6 +287,11 @@ static int validate_sb_layout(struct bch_sb_layout *layout, struct printbuf *out
>>>    		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
>>>    	}
>>> +	if (layout->sb_max_size_bits > BCH_SB_LAYOUT_SIZE_BITS_MAX) {
>>> +		prt_printf(out, "Invalid superblock layout: max_size_bits too high");
>>> +		return -BCH_ERR_invalid_sb_layout_sb_max_size_bits;
>>> +	}
>>> +
>>>    	max_sectors = 1 << layout->sb_max_size_bits;
>>>    	prev_offset = le64_to_cpu(layout->sb_offset[0]);
>>
>> Wondering if this other patch might be considered more correct to prevent
>> shift oob, given also [0]:
> 
> Your first patch looks better, we want to know if we're feeding it
> garbage
> 

Understood. Thanks Kent.
Have a nice day,
--Gian
>>
>> diff --git a/fs/bcachefs/super-io.c b/fs/bcachefs/super-io.c
>> index ce7410d72089..428172897501 100644
>> --- a/fs/bcachefs/super-io.c
>> +++ b/fs/bcachefs/super-io.c
>> @@ -287,7 +287,7 @@ static int validate_sb_layout(struct bch_sb_layout
>> *layout, struct printbuf *out
>>   		return -BCH_ERR_invalid_sb_layout_nr_superblocks;
>>   	}
>>
>> -	max_sectors = 1 << layout->sb_max_size_bits;
>> +	max_sectors = 1 << min(BCH_SB_LAYOUT_SIZE_BITS_MAX,
>> layout->sb_max_size_bits);
>>
>>   	prev_offset = le64_to_cpu(layout->sb_offset[0]);
>>
>> Also this patch was already tested by syzbot [1]
>>
>> [0] 71dac2482ad3c8d4a8b8998a96751f009bad895f ("bcachefs:
>> BCH_SB_LAYOUT_SIZE_BITS_MAX")
>> [1] https://syzkaller.appspot.com/x/log.txt?x=1640b640580000
>>
>> Thanks for your time,
>>
>> -- Gian
>>

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