Re: + mseal-fix-is_madv_discard.patch added to mm-hotfixes-unstable branch

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On Wed, Aug 7, 2024 at 11:59 AM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>
> The patch titled
>      Subject: mseal: fix is_madv_discard()
> has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
>      mseal-fix-is_madv_discard.patch
>
> This patch will shortly appear at
>      https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mseal-fix-is_madv_discard.patch
>
> This patch will later appear in the mm-hotfixes-unstable branch at
>     git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
>
> Before you just go and hit "reply", please:
>    a) Consider who else should be cc'ed
>    b) Prefer to cc a suitable mailing list as well
>    c) Ideally: find the original patch on the mailing list and do a
>       reply-to-all to that, adding suitable additional cc's
>
> *** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
>
> The -mm tree is included into linux-next via the mm-everything
> branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
> and is updated there every 2-3 working days
>
> ------------------------------------------------------
> From: Pedro Falcato <pedro.falcato@xxxxxxxxx>
> Subject: mseal: fix is_madv_discard()
> Date: Wed, 7 Aug 2024 18:33:35 +0100
>
> is_madv_discard did its check wrong. MADV_ flags are not bitwise,
> they're normal sequential numbers. So, for instance:
>         behavior & (/* ... */ | MADV_REMOVE)
>
> tagged both MADV_REMOVE and MADV_RANDOM (bit 0 set) as
> discard operations. This is obviously incorrect, so use
> a switch statement instead.
>
> Link: https://lkml.kernel.org/r/20240807173336.2523757-1-pedro.falcato@xxxxxxxxx
> Link: https://lkml.kernel.org/r/20240807173336.2523757-2-pedro.falcato@xxxxxxxxx
> Fixes: 8be7258aad44 ("mseal: add mseal syscall")
> Signed-off-by: Pedro Falcato <pedro.falcato@xxxxxxxxx>
> Cc: Jeff Xu <jeffxu@xxxxxxxxxxxx>
> Cc: Kees Cook <kees@xxxxxxxxxx>
> Cc: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
> Cc: Shuah Khan <shuah@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
    Tested-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>
    Reviewed-by: Jeff Xu <jeffxu@xxxxxxxxxxxx>

In case needed.
Thanks
-Jeff

> ---
>
>  mm/mseal.c |   14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
>
> --- a/mm/mseal.c~mseal-fix-is_madv_discard
> +++ a/mm/mseal.c
> @@ -40,9 +40,17 @@ static bool can_modify_vma(struct vm_are
>
>  static bool is_madv_discard(int behavior)
>  {
> -       return  behavior &
> -               (MADV_FREE | MADV_DONTNEED | MADV_DONTNEED_LOCKED |
> -                MADV_REMOVE | MADV_DONTFORK | MADV_WIPEONFORK);
> +       switch (behavior) {
> +       case MADV_FREE:
> +       case MADV_DONTNEED:
> +       case MADV_DONTNEED_LOCKED:
> +       case MADV_REMOVE:
> +       case MADV_DONTFORK:
> +       case MADV_WIPEONFORK:
> +               return true;
> +       }
> +
> +       return false;
>  }
>
>  static bool is_ro_anon(struct vm_area_struct *vma)
> _
>
> Patches currently in -mm which might be from pedro.falcato@xxxxxxxxx are
>
> mseal-fix-is_madv_discard.patch
> selftests-mm-add-mseal-test-for-no-discard-madvise.patch
>





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