Re: [PATCH v3] mm/memfd: add F_SEAL_EXEC

[Kees Cook]

On Fri, Dec 02, 2022 at 01:33:59AM +0000, jeffxu@xxxxxxxxxxxx wrote:
> From: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
> 
> The new F_SEAL_EXEC flag will prevent modification of the exec bits:
> written as traditional octal mask, 0111, or as named flags, S_IXUSR |
> S_IXGRP | S_IXOTH. Any chmod(2) or similar call that attempts to modify
> any of these bits after the seal is applied will fail with errno EPERM.
> 
> This will preserve the execute bits as they are at the time of sealing,
> so the memfd will become either permanently executable or permanently
> un-executable.
> 
> Co-developed-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> Signed-off-by: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>

Oh, one note on tag ordering here. Since you're sending it, I would
expect this to read as:

  From: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
  ...
  Signed-off-by: Daniel Verkamp <dverkamp@xxxxxxxxxxxx>
  Co-developed-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
  Signed-off-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>

-- 
Kees Cook