[pbs-devel] [PATCH proxmox-backup] tape: mam: actually enforcing the length when writing attributes

[pbs-devel] [PATCH proxmox-backup] tape: mam: actually enforcing the length when writing attributes

[Dominik Csapak]

we have to check against the length of the attribute, not the u16
maximum value.

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
 pbs-tape/src/sg_tape/mam.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pbs-tape/src/sg_tape/mam.rs b/pbs-tape/src/sg_tape/mam.rs
index 4e995d0b..dc5163a5 100644
--- a/pbs-tape/src/sg_tape/mam.rs
+++ b/pbs-tape/src/sg_tape/mam.rs
@@ -169,7 +169,7 @@ pub fn write_mam_attribute<F: AsRawFd>(
     attr_data.extend(data);
     if !data.is_empty() && data.len() < attribute.len as usize {
         attr_data.resize(attr_data.len() - data.len() + attribute.len as usize, 0);
-    } else if data.len() > u16::MAX as usize {
+    } else if data.len() > attribute.len as usize {
         bail!("data to long");
     }
 
-- 
2.39.2



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Re: [pbs-devel] [PATCH proxmox-backup] tape: mam: actually enforcing the length when writing attributes

[Thomas Lamprecht]

Am 23/05/2024 um 12:08 schrieb Dominik Csapak:
> we have to check against the length of the attribute, not the u16
> maximum value.
> 
> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
> ---
>  pbs-tape/src/sg_tape/mam.rs | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/pbs-tape/src/sg_tape/mam.rs b/pbs-tape/src/sg_tape/mam.rs
> index 4e995d0b..dc5163a5 100644
> --- a/pbs-tape/src/sg_tape/mam.rs
> +++ b/pbs-tape/src/sg_tape/mam.rs
> @@ -169,7 +169,7 @@ pub fn write_mam_attribute<F: AsRawFd>(
>      attr_data.extend(data);
>      if !data.is_empty() && data.len() < attribute.len as usize {
>          attr_data.resize(attr_data.len() - data.len() + attribute.len as usize, 0);
> -    } else if data.len() > u16::MAX as usize {
> +    } else if data.len() > attribute.len as usize {
>          bail!("data to long");

Can we extend this error with the attribute name, the length we got and
the defined max length to have some more info for when a user runs into
this?

Something like:

bail!("attribute '{}' length {} is over the maximum allowed length {}", ...);

Or is this error already extended/concatenated with similar info somewhere
in the return chain (sorry, just doing a quick review directly in my MUA)


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Re: [pbs-devel] [PATCH proxmox-backup] tape: mam: actually enforcing the length when writing attributes

[Dominik Csapak]

On 5/24/24 09:50, Thomas Lamprecht wrote:
> Am 23/05/2024 um 12:08 schrieb Dominik Csapak:
>> we have to check against the length of the attribute, not the u16
>> maximum value.
>>
>> Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
>> ---
>>   pbs-tape/src/sg_tape/mam.rs | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/pbs-tape/src/sg_tape/mam.rs b/pbs-tape/src/sg_tape/mam.rs
>> index 4e995d0b..dc5163a5 100644
>> --- a/pbs-tape/src/sg_tape/mam.rs
>> +++ b/pbs-tape/src/sg_tape/mam.rs
>> @@ -169,7 +169,7 @@ pub fn write_mam_attribute<F: AsRawFd>(
>>       attr_data.extend(data);
>>       if !data.is_empty() && data.len() < attribute.len as usize {
>>           attr_data.resize(attr_data.len() - data.len() + attribute.len as usize, 0);
>> -    } else if data.len() > u16::MAX as usize {
>> +    } else if data.len() > attribute.len as usize {
>>           bail!("data to long");
> 
> Can we extend this error with the attribute name, the length we got and
> the defined max length to have some more info for when a user runs into
> this?
> 
> Something like:
> 
> bail!("attribute '{}' length {} is over the maximum allowed length {}", ...);
> 
> Or is this error already extended/concatenated with similar info somewhere
> in the return chain (sorry, just doing a quick review directly in my MUA)


it's logged with:

could not set MAM attribute {id}: {err}

and from the id we can infer the maximum length

but printing the expected/actual len probably make sense


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Re: [pbs-devel] [PATCH proxmox-backup] tape: mam: actually enforcing the length when writing attributes

[Thomas Lamprecht]

Am 24/05/2024 um 10:19 schrieb Dominik Csapak:
> On 5/24/24 09:50, Thomas Lamprecht wrote:
>> Am 23/05/2024 um 12:08 schrieb Dominik Csapak:
>>> +    } else if data.len() > attribute.len as usize {
>>>           bail!("data to long");
>>
>> Can we extend this error with the attribute name, the length we got and
>> the defined max length to have some more info for when a user runs into
>> this?
>>
>> Something like:
>>
>> bail!("attribute '{}' length {} is over the maximum allowed length {}", ...);
>>
>> Or is this error already extended/concatenated with similar info somewhere
>> in the return chain (sorry, just doing a quick review directly in my MUA)
> 
> 
> it's logged with:
> 
> could not set MAM attribute {id}: {err}

OK, thanks for checking.

> and from the id we can infer the maximum length

It still is nice for the end user to get to see that, if some (description
or label) attribute would become more free form in the future, even if
we'd say that's unlikely it's IMO just way to cheap to even thinking about
not doing it..

> 
> but printing the expected/actual len probably make sense
> 

Yeah, please print both, got and expected.



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