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Message-ID: <CABi2SkXHyF+dHo7Rv5V1jPZ4B5_v4Hva-A4XphtRMQJTrw_jqQ@mail.gmail.com>
Date: Thu, 24 Jul 2025 11:40:01 -0700
From: Jeff Xu <jeffxu@...omium.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, "Liam R . Howlett" <Liam.Howlett@...cle.com>,
David Hildenbrand <david@...hat.com>, Vlastimil Babka <vbabka@...e.cz>, Jann Horn <jannh@...gle.com>,
Pedro Falcato <pfalcato@...e.de>, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Kees Cook <kees@...nel.org>, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3 3/5] mm/mseal: small cleanups
Hi Lorenzo,
On Wed, Jul 16, 2025 at 10:38 AM Lorenzo Stoakes
<lorenzo.stoakes@...cle.com> wrote:
>
> Drop the wholly unnecessary set_vma_sealed() helper(), which is used only
> once, and place VMA_ITERATOR() declarations in the correct place.
>
> Retain vma_is_sealed(), and use it instead of the confusingly named
> can_modify_vma(), so it's abundantly clear what's being tested, rather then
> a nebulous sense of 'can the VMA be modified'.
>
> No functional change intended.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> Reviewed-by: Pedro Falcato <pfalcato@...e.de>
> Acked-by: David Hildenbrand <david@...hat.com>
Acked-by: Jeff Xu <jeffxu@...omium.org>
Thanks and regards
-Jeff
> ---
> mm/madvise.c | 2 +-
> mm/mprotect.c | 2 +-
> mm/mremap.c | 2 +-
> mm/mseal.c | 9 +--------
> mm/vma.c | 4 ++--
> mm/vma.h | 20 ++------------------
> 6 files changed, 8 insertions(+), 31 deletions(-)
>
> diff --git a/mm/madvise.c b/mm/madvise.c
> index dc3d8497b0f4..da6e0e7c00b5 100644
> --- a/mm/madvise.c
> +++ b/mm/madvise.c
> @@ -1286,7 +1286,7 @@ static bool can_madvise_modify(struct madvise_behavior *madv_behavior)
> struct vm_area_struct *vma = madv_behavior->vma;
>
> /* If the VMA isn't sealed we're good. */
> - if (can_modify_vma(vma))
> + if (!vma_is_sealed(vma))
> return true;
>
> /* For a sealed VMA, we only care about discard operations. */
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> index 88709c01177b..807939177065 100644
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -605,7 +605,7 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
> unsigned long charged = 0;
> int error;
>
> - if (!can_modify_vma(vma))
> + if (vma_is_sealed(vma))
> return -EPERM;
>
> if (newflags == oldflags) {
> diff --git a/mm/mremap.c b/mm/mremap.c
> index 5b7fe8f36074..8e93eca86721 100644
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -1649,7 +1649,7 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
> return -EFAULT;
>
> /* If mseal()'d, mremap() is prohibited. */
> - if (!can_modify_vma(vma))
> + if (vma_is_sealed(vma))
> return -EPERM;
>
> /* Align to hugetlb page size, if required. */
> diff --git a/mm/mseal.c b/mm/mseal.c
> index 1308e88ab184..adbcc65e9660 100644
> --- a/mm/mseal.c
> +++ b/mm/mseal.c
> @@ -15,11 +15,6 @@
> #include <linux/sched.h>
> #include "internal.h"
>
> -static inline void set_vma_sealed(struct vm_area_struct *vma)
> -{
> - vm_flags_set(vma, VM_SEALED);
> -}
> -
> static int mseal_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
> struct vm_area_struct **prev, unsigned long start,
> unsigned long end, vm_flags_t newflags)
> @@ -36,7 +31,7 @@ static int mseal_fixup(struct vma_iterator *vmi, struct vm_area_struct *vma,
> goto out;
> }
>
> - set_vma_sealed(vma);
> + vm_flags_set(vma, VM_SEALED);
> out:
> *prev = vma;
> return ret;
> @@ -53,7 +48,6 @@ static int check_mm_seal(unsigned long start, unsigned long end)
> {
> struct vm_area_struct *vma;
> unsigned long nstart = start;
> -
> VMA_ITERATOR(vmi, current->mm, start);
>
> /* going through each vma to check. */
> @@ -78,7 +72,6 @@ static int apply_mm_seal(unsigned long start, unsigned long end)
> {
> unsigned long nstart;
> struct vm_area_struct *vma, *prev;
> -
> VMA_ITERATOR(vmi, current->mm, start);
>
> vma = vma_iter_load(&vmi);
> diff --git a/mm/vma.c b/mm/vma.c
> index fc502b741dcf..75fd2759964b 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -1351,7 +1351,7 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
> }
>
> /* Don't bother splitting the VMA if we can't unmap it anyway */
> - if (!can_modify_vma(vms->vma)) {
> + if (vma_is_sealed(vms->vma)) {
> error = -EPERM;
> goto start_split_failed;
> }
> @@ -1371,7 +1371,7 @@ static int vms_gather_munmap_vmas(struct vma_munmap_struct *vms,
> for_each_vma_range(*(vms->vmi), next, vms->end) {
> long nrpages;
>
> - if (!can_modify_vma(next)) {
> + if (vma_is_sealed(next)) {
> error = -EPERM;
> goto modify_vma_failed;
> }
> diff --git a/mm/vma.h b/mm/vma.h
> index 85db5e880fcc..b123a9cdedb0 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -559,31 +559,15 @@ struct vm_area_struct *vma_iter_next_rewind(struct vma_iterator *vmi,
> }
>
> #ifdef CONFIG_64BIT
> -
> static inline bool vma_is_sealed(struct vm_area_struct *vma)
> {
> return (vma->vm_flags & VM_SEALED);
> }
> -
> -/*
> - * check if a vma is sealed for modification.
> - * return true, if modification is allowed.
> - */
> -static inline bool can_modify_vma(struct vm_area_struct *vma)
> -{
> - if (unlikely(vma_is_sealed(vma)))
> - return false;
> -
> - return true;
> -}
> -
> #else
> -
> -static inline bool can_modify_vma(struct vm_area_struct *vma)
> +static inline bool vma_is_sealed(struct vm_area_struct *vma)
> {
> - return true;
> + return false;
> }
> -
> #endif
>
> #if defined(CONFIG_STACK_GROWSUP)
> --
> 2.50.1
>
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