[PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[Xu Kuohai]

From: Xu Kuohai <xukuohai@huawei.com>

Function __copy_map_value and zero_map_value miscalculated copy offset,
resulting in possible copy of unwanted data to user or kernel.

Fix it.

Fixes: cc48755808c6 ("bpf: Add zero_map_value to zero map value with special fields")
Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
---
 include/linux/bpf.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 74c6f449d81e..c1bd1bd10506 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -315,7 +315,7 @@ static inline void __copy_map_value(struct bpf_map *map, void *dst, void *src, b
 		u32 next_off = map->off_arr->field_off[i];
 
 		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
-		curr_off += map->off_arr->field_sz[i];
+		curr_off = next_off + map->off_arr->field_sz[i];
 	}
 	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
 }
@@ -344,7 +344,7 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
 		u32 next_off = map->off_arr->field_off[i];
 
 		memset(dst + curr_off, 0, next_off - curr_off);
-		curr_off += map->off_arr->field_sz[i];
+		curr_off = next_off + map->off_arr->field_sz[i];
 	}
 	memset(dst + curr_off, 0, map->value_size - curr_off);
 }
-- 
2.30.2

Re: [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[sdf]

On 11/11, Xu Kuohai wrote:
> From: Xu Kuohai <xukuohai@huawei.com>

> Function __copy_map_value and zero_map_value miscalculated copy offset,
> resulting in possible copy of unwanted data to user or kernel.

> Fix it.

> Fixes: cc48755808c6 ("bpf: Add zero_map_value to zero map value with  
> special fields")
> Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
> ---
>   include/linux/bpf.h | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 74c6f449d81e..c1bd1bd10506 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -315,7 +315,7 @@ static inline void __copy_map_value(struct bpf_map  
> *map, void *dst, void *src, b
>   		u32 next_off = map->off_arr->field_off[i];

>   		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
> -		curr_off += map->off_arr->field_sz[i];
> +		curr_off = next_off + map->off_arr->field_sz[i];
>   	}
>   	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
>   }
> @@ -344,7 +344,7 @@ static inline void zero_map_value(struct bpf_map  
> *map, void *dst)
>   		u32 next_off = map->off_arr->field_off[i];

>   		memset(dst + curr_off, 0, next_off - curr_off);
> -		curr_off += map->off_arr->field_sz[i];
> +		curr_off = next_off + map->off_arr->field_sz[i];
>   	}
>   	memset(dst + curr_off, 0, map->value_size - curr_off);
>   }

Hmm, does it mean that it currently works only for the cases where
these special fields are first/last?

Also, what about bpf-next? The same problem seem to exist there?

Might be a good idea to have some selftest to exercise this?

> --
> 2.30.2

Re: [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[Kumar Kartikeya Dwivedi]

On Sat, Nov 12, 2022 at 12:47:52AM IST, sdf@google.com wrote:
> On 11/11, Xu Kuohai wrote:
> > From: Xu Kuohai <xukuohai@huawei.com>
>
> > Function __copy_map_value and zero_map_value miscalculated copy offset,
> > resulting in possible copy of unwanted data to user or kernel.
>
> > Fix it.
>
> > Fixes: cc48755808c6 ("bpf: Add zero_map_value to zero map value with
> > special fields")
> > Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
> > Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
> > ---
> >   include/linux/bpf.h | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
>
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index 74c6f449d81e..c1bd1bd10506 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -315,7 +315,7 @@ static inline void __copy_map_value(struct bpf_map
> > *map, void *dst, void *src, b
> >   		u32 next_off = map->off_arr->field_off[i];
>
> >   		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
> > -		curr_off += map->off_arr->field_sz[i];
> > +		curr_off = next_off + map->off_arr->field_sz[i];
> >   	}
> >   	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
> >   }
> > @@ -344,7 +344,7 @@ static inline void zero_map_value(struct bpf_map
> > *map, void *dst)
> >   		u32 next_off = map->off_arr->field_off[i];
>
> >   		memset(dst + curr_off, 0, next_off - curr_off);
> > -		curr_off += map->off_arr->field_sz[i];
> > +		curr_off = next_off + map->off_arr->field_sz[i];
> >   	}
> >   	memset(dst + curr_off, 0, map->value_size - curr_off);
> >   }
>
> Hmm, does it mean that it currently works only for the cases where
> these special fields are first/last?
>
> Also, what about bpf-next? The same problem seem to exist there?
>

Replied with the patch in the other email.

> Might be a good idea to have some selftest to exercise this?
>

I agree, there was another bug in the same code before this, so I think we
should add tests for this (I should have done that with the commit being
fixed...).

Xu, if you have cycles, can you work on testing a few edge cases and make sure
we don't regress in the future? Otherwise I will take a look next week.

Re: [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[Xu Kuohai]

On 11/12/2022 4:45 AM, Kumar Kartikeya Dwivedi wrote:
> On Sat, Nov 12, 2022 at 12:47:52AM IST, sdf@google.com wrote:
>> On 11/11, Xu Kuohai wrote:
>>> From: Xu Kuohai <xukuohai@huawei.com>
>>
>>> Function __copy_map_value and zero_map_value miscalculated copy offset,
>>> resulting in possible copy of unwanted data to user or kernel.
>>
>>> Fix it.
>>
>>> Fixes: cc48755808c6 ("bpf: Add zero_map_value to zero map value with
>>> special fields")
>>> Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
>>> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
>>> ---
>>>    include/linux/bpf.h | 4 ++--
>>>    1 file changed, 2 insertions(+), 2 deletions(-)
>>
>>> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
>>> index 74c6f449d81e..c1bd1bd10506 100644
>>> --- a/include/linux/bpf.h
>>> +++ b/include/linux/bpf.h
>>> @@ -315,7 +315,7 @@ static inline void __copy_map_value(struct bpf_map
>>> *map, void *dst, void *src, b
>>>    		u32 next_off = map->off_arr->field_off[i];
>>
>>>    		memcpy(dst + curr_off, src + curr_off, next_off - curr_off);
>>> -		curr_off += map->off_arr->field_sz[i];
>>> +		curr_off = next_off + map->off_arr->field_sz[i];
>>>    	}
>>>    	memcpy(dst + curr_off, src + curr_off, map->value_size - curr_off);
>>>    }
>>> @@ -344,7 +344,7 @@ static inline void zero_map_value(struct bpf_map
>>> *map, void *dst)
>>>    		u32 next_off = map->off_arr->field_off[i];
>>
>>>    		memset(dst + curr_off, 0, next_off - curr_off);
>>> -		curr_off += map->off_arr->field_sz[i];
>>> +		curr_off = next_off + map->off_arr->field_sz[i];
>>>    	}
>>>    	memset(dst + curr_off, 0, map->value_size - curr_off);
>>>    }
>>
>> Hmm, does it mean that it currently works only for the cases where
>> these special fields are first/last?
>>
>> Also, what about bpf-next? The same problem seem to exist there?
>>
> 
> Replied with the patch in the other email.
> 
>> Might be a good idea to have some selftest to exercise this?
>>
> 
> I agree, there was another bug in the same code before this, so I think we
> should add tests for this (I should have done that with the commit being
> fixed...).
> 
> Xu, if you have cycles, can you work on testing a few edge cases and make sure
> we don't regress in the future? Otherwise I will take a look next week.
> .

Ok, I'll add a few cases to test_sk_storage_map to capture this

Re: [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[Kumar Kartikeya Dwivedi]

On Fri, Nov 11, 2022 at 06:26:20PM IST, Xu Kuohai wrote:
> From: Xu Kuohai <xukuohai@huawei.com>
>
> Function __copy_map_value and zero_map_value miscalculated copy offset,
> resulting in possible copy of unwanted data to user or kernel.
>
> Fix it.
>
> Fixes: cc48755808c6 ("bpf: Add zero_map_value to zero map value with special fields")
> Fixes: 4d7d7f69f4b1 ("bpf: Adapt copy_map_value for multiple offset case")
> Signed-off-by: Xu Kuohai <xukuohai@huawei.com>
> ---

Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

I also have a fix here for bpf-next, since this won't apply to it:
https://lore.kernel.org/bpf/20221111193224.876706-4-memxor@gmail.com

I think it'd be best if this one gets applied to bpf and mine to bpf-next, and
any conflicts are resolved when merging both trees (the conflict is trivial),
but I'll leave it up to the maintainers to decide.

Re: [PATCH bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf.git (master)
by Andrii Nakryiko <andrii@kernel.org>:

On Fri, 11 Nov 2022 07:56:20 -0500 you wrote:
> From: Xu Kuohai <xukuohai@huawei.com>
> 
> Function __copy_map_value and zero_map_value miscalculated copy offset,
> resulting in possible copy of unwanted data to user or kernel.
> 
> Fix it.
> 
> [...]

Here is the summary with links:
  - [bpf] bpf: Fix offset calculation error in __copy_map_value and zero_map_value
    https://git.kernel.org/bpf/bpf/c/1f6e04a1c7b8

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html