Re: [PATCH v2] debugfs: Fix lockdown check for mmap_prepare

[Lorenzo Stoakes]

On Mon, Jun 15, 2026 at 06:47:50PM +0800, Chun-Yi Lee wrote:
> From: Chun-Yi Lee <jlee@xxxxxxxx>
>
> Commit 651fdda8406d ("relay: update relay to use mmap_prepare")
> changed the `mmap` file operation to `mmap_prepare` for relayfs, but
> the lockdown check in debugfs was not updated accordingly.
>
> This prevents debugfs from being locked down when the kernel is in
> integrity mode if a file uses `mmap_prepare` but not `mmap`.
>
> Since the conversion to `mmap_prepare` across the kernel is not yet
> complete, update the lockdown check to look for both `mmap` and
> `mmap_prepare` to ensure comprehensive coverage.
>
> Fixes: 651fdda8406d ("relay: update relay to use mmap_prepare")
> Signed-off-by: Chun-Yi Lee <jlee@xxxxxxxx>

LGTM so:

Reviewed-by: Lorenzo Stoakes <ljs@xxxxxxxxxx>

> Cc: David Howells <dhowells@xxxxxxxxxx>
> Cc: Lorenzo Stoakes <ljs@xxxxxxxxxx>
> Cc: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Rafael J. Wysocki <rafael@xxxxxxxxxx>
> Cc: Matthew Garrett <mjg59@xxxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Cc: Danilo Krummrich <dakr@xxxxxxxxxx>
> Cc: driver-core@xxxxxxxxxxxxxxx
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> v2:
> - Add explicit From tag to match Signed-off-by.
> - Fix Lorenzo's email address.
> - Add Cc stable for backporting.
> - Check both mmap and mmap_prepare as suggested by Lorenzo.
>
>  fs/debugfs/file.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
> index edd6aafbfbaa..08de6652a4f3 100644
> --- a/fs/debugfs/file.c
> +++ b/fs/debugfs/file.c
> @@ -273,7 +273,8 @@ static int debugfs_locked_down(struct inode *inode,
>  	    (!real_fops ||
>  	     (!real_fops->unlocked_ioctl &&
>  	      !real_fops->compat_ioctl &&
> -	      !real_fops->mmap)))
> +	      !real_fops->mmap &&
> +	      !real_fops->mmap_prepare)))
>  		return 0;
>
>  	if (security_locked_down(LOCKDOWN_DEBUGFS))
> --
> 2.43.0
>

Cheers, Lorenzo