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

[Jiri Olsa]

On Thu, Mar 06, 2025 at 01:06:58PM +0800, Chen Linxuan wrote:
> Backport of a similar change from commit 5ac9b4e935df ("lib/buildid:
> Handle memfd_secret() files in build_id_parse()") to address an issue
> where accessing secret memfd contents through build_id_parse() would
> trigger faults.
> 
> Original report and repro can be found in [0].
> 
>   [0] https://lore.kernel.org/bpf/ZwyG8Uro%2FSyTXAni@ly-workstation/
> 
> This repro will cause BUG: unable to handle kernel paging request in
> build_id_parse in 5.15/6.1/6.6.

hi,
so this patch is meant for one of 5.15/6.1/6.6?

if so you need to send it separately and add that to the subject,
please check Documentation/process/stable-kernel-rules.rst

and you can check other stable kernel patches on the mailing list
like [1][2]

thanks,
jirka


[1] https://lore.kernel.org/bpf/20241206153403.273068-2-daniel@xxxxxxxxxxxxx/
[2] https://lore.kernel.org/bpf/20241104175256.2327164-3-jolsa@xxxxxxxxxx/

> 
> Some other discussions can be found in [1].
> 
>   [1] https://lore.kernel.org/bpf/20241104175256.2327164-1-jolsa@xxxxxxxxxx/T/#u
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 88a16a130933 ("perf: Add build id data in mmap2 event")
> Signed-off-by: Chen Linxuan <chenlinxuan@xxxxxxxxxx>
> ---
>  lib/buildid.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/lib/buildid.c b/lib/buildid.c
> index 9fc46366597e..b78d119ed1f7 100644
> --- a/lib/buildid.c
> +++ b/lib/buildid.c
> @@ -157,6 +157,12 @@ int build_id_parse(struct vm_area_struct *vma, unsigned char *build_id,
>  	if (!vma->vm_file)
>  		return -EINVAL;
>  
> +#ifdef CONFIG_SECRETMEM
> +	/* reject secretmem folios created with memfd_secret() */
> +	if (vma->vm_file->f_mapping->a_ops == &secretmem_aops)
> +		return -EFAULT;
> +#endif
> +
>  	page = find_get_page(vma->vm_file->f_mapping, 0);
>  	if (!page)
>  		return -EFAULT;	/* page not mapped */
> -- 
> 2.48.1
>