Re: [REGRESSION][BISECTED] erroneous buffer overflow detected in bch2_xattr_validate

[Alan Huang]

Thanks,
Alan



> On May 2, 2025, at 01:22, Jan Hendrik Farr <kernel@xxxxxxxx> wrote:
> 
>> 
>> I wonder if the __counted_by(x_name_len) in struct bch_xattr is needed, since there is also a value after x_name.
> 
> Wait a minute. Are you saying that the value with length x_val_len
> is behind the name (of length x_name_len) at the end of the struct.
> So essentially the flexible array member x_name has a length of
> x_name_len + x_val_len and contains both the name and value?

Yes.

> 
> If that's the case:
> 
> 1. that's not at all clear from the struct definition
> 2. __counted_by(x_name_len) is not correct in that case
> 

Both clang and gcc say:

    • p->array has at least p->count number of elements available all the time. 

Note the at least here. Though I think the counted_by is misleading here.

> 
> Best Regards
> Jan