vma_adjust modifies a VMA and possibly its neighbors. Mark them as locked
before making the modifications.
Signed-off-by: Suren Baghdasaryan <[email protected]>
---
mm/mmap.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/mm/mmap.c b/mm/mmap.c
index f89c9b058105..ed58cf0689b2 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -710,6 +710,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
long adjust_next = 0;
int remove_next = 0;
+ vma_mark_locked(vma);
+ if (next)
+ vma_mark_locked(next);
+
if (next && !insert) {
struct vm_area_struct *exporter = NULL, *importer = NULL;
@@ -754,8 +758,11 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
* If next doesn't have anon_vma, import from vma after
* next, if the vma overlaps with it.
*/
- if (remove_next == 2 && !next->anon_vma)
+ if (remove_next == 2 && !next->anon_vma) {
exporter = next->vm_next;
+ if (exporter)
+ vma_mark_locked(exporter);
+ }
} else if (end > next->vm_start) {
/*
@@ -931,6 +938,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
* "vma->vm_next" gap must be updated.
*/
next = vma->vm_next;
+ if (next)
+ vma_mark_locked(next);
} else {
/*
* For the scope of the comment "next" and
--
2.37.2.789.g6183377224-goog
Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit :
> vma_adjust modifies a VMA and possibly its neighbors. Mark them as locked
> before making the modifications.
>
> Signed-off-by: Suren Baghdasaryan <[email protected]>
> ---
> mm/mmap.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index f89c9b058105..ed58cf0689b2 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -710,6 +710,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> long adjust_next = 0;
> int remove_next = 0;
>
> + vma_mark_locked(vma);
> + if (next)
> + vma_mark_locked(next);
> +
I was wondering if the VMAs insert and expand should be locked too.
For expand, I can't see any valid reason, but for insert, I'm puzzled.
I would think that it is better to lock the VMA to be inserted but I can't
really justify that.
It may be nice to detail why this is not need to lock insert and expand here.
> if (next && !insert) {
> struct vm_area_struct *exporter = NULL, *importer = NULL;
>
> @@ -754,8 +758,11 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> * If next doesn't have anon_vma, import from vma after
> * next, if the vma overlaps with it.
> */
> - if (remove_next == 2 && !next->anon_vma)
> + if (remove_next == 2 && !next->anon_vma) {
> exporter = next->vm_next;
> + if (exporter)
> + vma_mark_locked(exporter);
> + }
>
> } else if (end > next->vm_start) {
> /*
> @@ -931,6 +938,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> * "vma->vm_next" gap must be updated.
> */
> next = vma->vm_next;
> + if (next)
> + vma_mark_locked(next);
> } else {
> /*
> * For the scope of the comment "next" and
On Tue, Sep 6, 2022 at 8:35 AM Laurent Dufour <[email protected]> wrote:
>
> Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit :
> > vma_adjust modifies a VMA and possibly its neighbors. Mark them as locked
> > before making the modifications.
> >
> > Signed-off-by: Suren Baghdasaryan <[email protected]>
> > ---
> > mm/mmap.c | 11 ++++++++++-
> > 1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/mmap.c b/mm/mmap.c
> > index f89c9b058105..ed58cf0689b2 100644
> > --- a/mm/mmap.c
> > +++ b/mm/mmap.c
> > @@ -710,6 +710,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> > long adjust_next = 0;
> > int remove_next = 0;
> >
> > + vma_mark_locked(vma);
> > + if (next)
> > + vma_mark_locked(next);
> > +
>
> I was wondering if the VMAs insert and expand should be locked too.
>
> For expand, I can't see any valid reason, but for insert, I'm puzzled.
> I would think that it is better to lock the VMA to be inserted but I can't
> really justify that.
>
> It may be nice to detail why this is not need to lock insert and expand here.
'expand' is always locked before it's passed to __vma_adjust() by
vma_merge(). It has to be locked before we decide "Can it merge with
the predecessor?" here
https://elixir.bootlin.com/linux/latest/source/mm/mmap.c#L1201 because
a change in VMA can affect that decision. I spent many hours tracking
the issue caused by not locking the VMA before making this decision.
It might be good to add a comment about this...
AFAIKT 'insert' is only used by __split_vma() and it's always a brand
new VMA which is not yet linked into mm->mmap. Any reason
__vma_adjust() should lock it?
>
> > if (next && !insert) {
> > struct vm_area_struct *exporter = NULL, *importer = NULL;
> >
> > @@ -754,8 +758,11 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> > * If next doesn't have anon_vma, import from vma after
> > * next, if the vma overlaps with it.
> > */
> > - if (remove_next == 2 && !next->anon_vma)
> > + if (remove_next == 2 && !next->anon_vma) {
> > exporter = next->vm_next;
> > + if (exporter)
> > + vma_mark_locked(exporter);
> > + }
> >
> > } else if (end > next->vm_start) {
> > /*
> > @@ -931,6 +938,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
> > * "vma->vm_next" gap must be updated.
> > */
> > next = vma->vm_next;
> > + if (next)
> > + vma_mark_locked(next);
> > } else {
> > /*
> > * For the scope of the comment "next" and
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
>
Le 09/09/2022 à 02:51, Suren Baghdasaryan a écrit :
> On Tue, Sep 6, 2022 at 8:35 AM Laurent Dufour <[email protected]> wrote:
>>
>> Le 01/09/2022 à 19:34, Suren Baghdasaryan a écrit :
>>> vma_adjust modifies a VMA and possibly its neighbors. Mark them as locked
>>> before making the modifications.
>>>
>>> Signed-off-by: Suren Baghdasaryan <[email protected]>
>>> ---
>>> mm/mmap.c | 11 ++++++++++-
>>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/mm/mmap.c b/mm/mmap.c
>>> index f89c9b058105..ed58cf0689b2 100644
>>> --- a/mm/mmap.c
>>> +++ b/mm/mmap.c
>>> @@ -710,6 +710,10 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
>>> long adjust_next = 0;
>>> int remove_next = 0;
>>>
>>> + vma_mark_locked(vma);
>>> + if (next)
>>> + vma_mark_locked(next);
>>> +
>>
>> I was wondering if the VMAs insert and expand should be locked too.
>>
>> For expand, I can't see any valid reason, but for insert, I'm puzzled.
>> I would think that it is better to lock the VMA to be inserted but I can't
>> really justify that.
>>
>> It may be nice to detail why this is not need to lock insert and expand here.
>
> 'expand' is always locked before it's passed to __vma_adjust() by
> vma_merge(). It has to be locked before we decide "Can it merge with
> the predecessor?" here
> https://elixir.bootlin.com/linux/latest/source/mm/mmap.c#L1201 because
> a change in VMA can affect that decision. I spent many hours tracking
> the issue caused by not locking the VMA before making this decision.
> It might be good to add a comment about this...
>
> AFAIKT 'insert' is only used by __split_vma() and it's always a brand
> new VMA which is not yet linked into mm->mmap. Any reason
> __vma_adjust() should lock it?
No, I think that's good this way.
>
>>
>>> if (next && !insert) {
>>> struct vm_area_struct *exporter = NULL, *importer = NULL;
>>>
>>> @@ -754,8 +758,11 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
>>> * If next doesn't have anon_vma, import from vma after
>>> * next, if the vma overlaps with it.
>>> */
>>> - if (remove_next == 2 && !next->anon_vma)
>>> + if (remove_next == 2 && !next->anon_vma) {
>>> exporter = next->vm_next;
>>> + if (exporter)
>>> + vma_mark_locked(exporter);
>>> + }
>>>
>>> } else if (end > next->vm_start) {
>>> /*
>>> @@ -931,6 +938,8 @@ int __vma_adjust(struct vm_area_struct *vma, unsigned long start,
>>> * "vma->vm_next" gap must be updated.
>>> */
>>> next = vma->vm_next;
>>> + if (next)
>>> + vma_mark_locked(next);
>>> } else {
>>> /*
>>> * For the scope of the comment "next" and
>>
>> --
>> To unsubscribe from this group and stop receiving emails from it, send an email to [email protected].
>>