Re: [PATCH bpf] lib/buildid: handle memfd_secret() files in build_id_parse()

[Shakeel Butt <shakeel.butt@linux.dev>]

On Mon, Oct 14, 2024 at 04:56:31PM GMT, Andrii Nakryiko wrote:
> From memfd_secret(2) manpage:
> 
>   The memory areas backing the file created with memfd_secret(2) are
>   visible only to the processes that have access to the file descriptor.
>   The memory region is removed from the kernel page tables and only the
>   page tables of the processes holding the file descriptor map the
>   corresponding physical memory. (Thus, the pages in the region can't be
>   accessed by the kernel itself, so that, for example, pointers to the
>   region can't be passed to system calls.)
> 
> We need to handle this special case gracefully in build ID fetching
> code. Return -EACCESS whenever secretmem file is passed to build_id_parse()
> family of APIs. Original report and repro can be found in [0].
> 
>   [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/
> 
> Reported-by: Yi Lai <yi1.lai@intel.com>
> Suggested-by: Shakeel Butt <shakeel.butt@linux.dev>
> Fixes: de3ec364c3c3 ("lib/buildid: add single folio-based file reader abstraction")
> Signed-off-by: Andrii Nakryiko <andrii@kernel.org>

Acked-by: Shakeel Butt <shakeel.butt@linux.dev>