* Re: [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent
2022-08-03 22:03 [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent Peter Xu
@ 2022-08-04 9:02 ` Vlastimil Babka (SUSE)
2022-08-04 11:01 ` David Hildenbrand
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: Vlastimil Babka (SUSE) @ 2022-08-04 9:02 UTC (permalink / raw)
To: Peter Xu, linux-kernel, linux-mm
Cc: Yang Shi, Andrew Morton, Nadav Amit, David Hildenbrand,
Konstantin Khlebnikov
On 8/4/22 00:03, Peter Xu wrote:
> These bits should only be valid when the ptes are present. Introducing two
> booleans for it and set it to false when !pte_present().
>
> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
> Fixes: b1d4d9e0cbd0 ("proc/smaps: carefully handle migration entries", 2012-05-31)
> Signed-off-by: Peter Xu <peterx@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
> ---
> fs/proc/task_mmu.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 9913f3be9fd2..482f91577f8c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> struct vm_area_struct *vma = walk->vma;
> bool locked = !!(vma->vm_flags & VM_LOCKED);
> struct page *page = NULL;
> - bool migration = false;
> + bool migration = false, young = false, dirty = false;
>
> if (pte_present(*pte)) {
> page = vm_normal_page(vma, addr, *pte);
> + young = pte_young(*pte);
> + dirty = pte_dirty(*pte);
> } else if (is_swap_pte(*pte)) {
> swp_entry_t swpent = pte_to_swp_entry(*pte);
>
> @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> if (!page)
> return;
>
> - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte),
> - locked, migration);
> + smaps_account(mss, page, false, young, dirty, locked, migration);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent
2022-08-03 22:03 [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent Peter Xu
2022-08-04 9:02 ` Vlastimil Babka (SUSE)
@ 2022-08-04 11:01 ` David Hildenbrand
2022-08-04 17:43 ` Yang Shi
2022-08-04 22:40 ` Andrew Morton
3 siblings, 0 replies; 6+ messages in thread
From: David Hildenbrand @ 2022-08-04 11:01 UTC (permalink / raw)
To: Peter Xu, linux-kernel, linux-mm
Cc: Yang Shi, Andrew Morton, Nadav Amit, Konstantin Khlebnikov
On 04.08.22 00:03, Peter Xu wrote:
> These bits should only be valid when the ptes are present. Introducing two
> booleans for it and set it to false when !pte_present().
>
> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
> Fixes: b1d4d9e0cbd0 ("proc/smaps: carefully handle migration entries", 2012-05-31)
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> fs/proc/task_mmu.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 9913f3be9fd2..482f91577f8c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> struct vm_area_struct *vma = walk->vma;
> bool locked = !!(vma->vm_flags & VM_LOCKED);
> struct page *page = NULL;
> - bool migration = false;
> + bool migration = false, young = false, dirty = false;
>
> if (pte_present(*pte)) {
> page = vm_normal_page(vma, addr, *pte);
> + young = pte_young(*pte);
> + dirty = pte_dirty(*pte);
> } else if (is_swap_pte(*pte)) {
> swp_entry_t swpent = pte_to_swp_entry(*pte);
>
> @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> if (!page)
> return;
>
> - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte),
> - locked, migration);
> + smaps_account(mss, page, false, young, dirty, locked, migration);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent
2022-08-03 22:03 [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent Peter Xu
2022-08-04 9:02 ` Vlastimil Babka (SUSE)
2022-08-04 11:01 ` David Hildenbrand
@ 2022-08-04 17:43 ` Yang Shi
2022-08-04 22:40 ` Andrew Morton
3 siblings, 0 replies; 6+ messages in thread
From: Yang Shi @ 2022-08-04 17:43 UTC (permalink / raw)
To: Peter Xu
Cc: linux-kernel, linux-mm, Andrew Morton, Nadav Amit,
David Hildenbrand, Konstantin Khlebnikov
On Wed, Aug 3, 2022 at 3:03 PM Peter Xu <peterx@redhat.com> wrote:
>
> These bits should only be valid when the ptes are present. Introducing two
> booleans for it and set it to false when !pte_present().
>
> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>
> Fixes: b1d4d9e0cbd0 ("proc/smaps: carefully handle migration entries", 2012-05-31)
> Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
> ---
> fs/proc/task_mmu.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 9913f3be9fd2..482f91577f8c 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> struct vm_area_struct *vma = walk->vma;
> bool locked = !!(vma->vm_flags & VM_LOCKED);
> struct page *page = NULL;
> - bool migration = false;
> + bool migration = false, young = false, dirty = false;
>
> if (pte_present(*pte)) {
> page = vm_normal_page(vma, addr, *pte);
> + young = pte_young(*pte);
> + dirty = pte_dirty(*pte);
> } else if (is_swap_pte(*pte)) {
> swp_entry_t swpent = pte_to_swp_entry(*pte);
>
> @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> if (!page)
> return;
>
> - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte),
> - locked, migration);
> + smaps_account(mss, page, false, young, dirty, locked, migration);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> --
> 2.32.0
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent
2022-08-03 22:03 [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent Peter Xu
` (2 preceding siblings ...)
2022-08-04 17:43 ` Yang Shi
@ 2022-08-04 22:40 ` Andrew Morton
2022-08-05 15:52 ` Peter Xu
3 siblings, 1 reply; 6+ messages in thread
From: Andrew Morton @ 2022-08-04 22:40 UTC (permalink / raw)
To: Peter Xu
Cc: linux-kernel, linux-mm, Yang Shi, Nadav Amit, David Hildenbrand,
Konstantin Khlebnikov
On Wed, 3 Aug 2022 18:03:29 -0400 Peter Xu <peterx@redhat.com> wrote:
> These bits should only be valid when the ptes are present. Introducing two
> booleans for it and set it to false when !pte_present().
Please (always) describe the user visible runtime effects of the bug
which is being fixed?
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> struct vm_area_struct *vma = walk->vma;
> bool locked = !!(vma->vm_flags & VM_LOCKED);
> struct page *page = NULL;
> - bool migration = false;
> + bool migration = false, young = false, dirty = false;
>
> if (pte_present(*pte)) {
> page = vm_normal_page(vma, addr, *pte);
> + young = pte_young(*pte);
> + dirty = pte_dirty(*pte);
> } else if (is_swap_pte(*pte)) {
> swp_entry_t swpent = pte_to_swp_entry(*pte);
>
> @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> if (!page)
> return;
>
> - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte),
> - locked, migration);
> + smaps_account(mss, page, false, young, dirty, locked, migration);
> }
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> --
> 2.32.0
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] mm/smaps: Don't access young/dirty bit if pte unpresent
2022-08-04 22:40 ` Andrew Morton
@ 2022-08-05 15:52 ` Peter Xu
0 siblings, 0 replies; 6+ messages in thread
From: Peter Xu @ 2022-08-05 15:52 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-kernel, linux-mm, Yang Shi, Nadav Amit, David Hildenbrand,
Konstantin Khlebnikov
On Thu, Aug 04, 2022 at 03:40:50PM -0700, Andrew Morton wrote:
> On Wed, 3 Aug 2022 18:03:29 -0400 Peter Xu <peterx@redhat.com> wrote:
>
> > These bits should only be valid when the ptes are present. Introducing two
> > booleans for it and set it to false when !pte_present().
>
> Please (always) describe the user visible runtime effects of the bug
> which is being fixed?
Will do in the future.
For this specific one I'll add some more details:
The bug is found during code reading and no real world issue reported,
but logically such an error can cause incorrect readings for either smaps
or smaps_rollup output on quite a few fields.
For example, it could cause over-estimate on values like Shared_Dirty,
Private_Dirty, Referenced; or it could also cause under-estimate on
values like LazyFree, Shared_Clean, Private_Clean.
Meanwhile I think I overlooked the pmd handling which seems to have the
same issue but done in another commit.. Will repost soon.
Thanks,
>
>
> > --- a/fs/proc/task_mmu.c
> > +++ b/fs/proc/task_mmu.c
> > @@ -527,10 +527,12 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> > struct vm_area_struct *vma = walk->vma;
> > bool locked = !!(vma->vm_flags & VM_LOCKED);
> > struct page *page = NULL;
> > - bool migration = false;
> > + bool migration = false, young = false, dirty = false;
> >
> > if (pte_present(*pte)) {
> > page = vm_normal_page(vma, addr, *pte);
> > + young = pte_young(*pte);
> > + dirty = pte_dirty(*pte);
> > } else if (is_swap_pte(*pte)) {
> > swp_entry_t swpent = pte_to_swp_entry(*pte);
> >
> > @@ -560,8 +562,7 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
> > if (!page)
> > return;
> >
> > - smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte),
> > - locked, migration);
> > + smaps_account(mss, page, false, young, dirty, locked, migration);
> > }
> >
> > #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> > --
> > 2.32.0
>
--
Peter Xu
^ permalink raw reply [flat|nested] 6+ messages in thread