2023-05-17 02:28:37

by Peter Collingbourne

Subject: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()

Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
the call to swap_free() before the call to set_pte_at(), which meant that
the MTE tags could end up being freed before set_pte_at() had a chance
to restore them. Fix it by adding a call to the arch_swap_restore() hook
before the call to swap_free().

Signed-off-by: Peter Collingbourne <[email protected]>
Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
Cc: <[email protected]> # 6.1
Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
Reported-by: Qun-wei Lin (林群崴) <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
---
v2:
- Call arch_swap_restore() directly instead of via arch_do_swap_page()

mm/memory.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/mm/memory.c b/mm/memory.c
index f69fbc251198..fc25764016b3 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3932,6 +3932,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
}
}

+ /*
+ * Some architectures may have to restore extra metadata to the page
+ * when reading from swap. This metadata may be indexed by swap entry
+ * so this must be called before swap_free().
+ */
+ arch_swap_restore(entry, folio);
+
/*
* Remove the swap entry and conditionally try to free up the swapcache.
* We're already holding a reference on the page but haven't mapped it
--
2.40.1.606.ga4b1b128d6-goog

2023-05-17 04:32:18

by Huang, Ying

Subject: Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()

Peter Collingbourne <[email protected]> writes:

> Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
> the call to swap_free() before the call to set_pte_at(), which meant that
> the MTE tags could end up being freed before set_pte_at() had a chance
> to restore them. Fix it by adding a call to the arch_swap_restore() hook
> before the call to swap_free().
>
> Signed-off-by: Peter Collingbourne <[email protected]>
> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
> Cc: <[email protected]> # 6.1
> Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
> Reported-by: Qun-wei Lin (林群崴) <[email protected]>
> Closes: https://lore.kernel.org/all/[email protected]/
> ---
> v2:
> - Call arch_swap_restore() directly instead of via arch_do_swap_page()
>
> mm/memory.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index f69fbc251198..fc25764016b3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3932,6 +3932,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> }
> }
>
> + /*
> + * Some architectures may have to restore extra metadata to the page
> + * when reading from swap. This metadata may be indexed by swap entry
> + * so this must be called before swap_free().
> + */
> + arch_swap_restore(entry, folio);
> +
> /*
> * Remove the swap entry and conditionally try to free up the swapcache.
> * We're already holding a reference on the page but haven't mapped it

Should you add

Suggested-by: David Hildenbrand <[email protected]>

for 1/3 and 2/3.

It looks good for me for swap code related part. Feel free to add

Acked-by: "Huang, Ying" <[email protected]>

to 1/3 and 2/3.

Best Regards,
Huang, Ying

2023-05-17 09:27:00

by David Hildenbrand

Subject: Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()

On 17.05.23 05:40, Huang, Ying wrote:
> Peter Collingbourne <[email protected]> writes:
>
>> Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
>> the call to swap_free() before the call to set_pte_at(), which meant that
>> the MTE tags could end up being freed before set_pte_at() had a chance
>> to restore them. Fix it by adding a call to the arch_swap_restore() hook
>> before the call to swap_free().
>>
>> Signed-off-by: Peter Collingbourne <[email protected]>
>> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
>> Cc: <[email protected]> # 6.1
>> Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
>> Reported-by: Qun-wei Lin (林群崴) <[email protected]>
>> Closes: https://lore.kernel.org/all/[email protected]/
>> ---
>> v2:
>> - Call arch_swap_restore() directly instead of via arch_do_swap_page()
>>
>> mm/memory.c | 7 +++++++
>> 1 file changed, 7 insertions(+)
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index f69fbc251198..fc25764016b3 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -3932,6 +3932,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>> }
>> }
>>
>> + /*
>> + * Some architectures may have to restore extra metadata to the page
>> + * when reading from swap. This metadata may be indexed by swap entry
>> + * so this must be called before swap_free().
>> + */
>> + arch_swap_restore(entry, folio);
>> +
>> /*
>> * Remove the swap entry and conditionally try to free up the swapcache.
>> * We're already holding a reference on the page but haven't mapped it
>
> Should you add
>
> Suggested-by: David Hildenbrand <[email protected]>
>
> for 1/3 and 2/3.

For 1/3, I think I rather only explained the problem in the first patch
and didn't really suggest this.

Acked-by: David Hildenbrand <[email protected]>

--
Thanks,

David / dhildenb

2023-05-17 15:07:36

by Steven Price

Subject: Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()

On 17/05/2023 03:21, Peter Collingbourne wrote:
> Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
> the call to swap_free() before the call to set_pte_at(), which meant that
> the MTE tags could end up being freed before set_pte_at() had a chance
> to restore them. Fix it by adding a call to the arch_swap_restore() hook
> before the call to swap_free().
>
> Signed-off-by: Peter Collingbourne <[email protected]>
> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
> Cc: <[email protected]> # 6.1
> Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
> Reported-by: Qun-wei Lin (林群崴) <[email protected]>
> Closes: https://lore.kernel.org/all/[email protected]/

Reviewed-by: Steven Price <[email protected]>

> ---
> v2:
> - Call arch_swap_restore() directly instead of via arch_do_swap_page()
>
> mm/memory.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index f69fbc251198..fc25764016b3 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3932,6 +3932,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
> }
> }
>
> + /*
> + * Some architectures may have to restore extra metadata to the page
> + * when reading from swap. This metadata may be indexed by swap entry
> + * so this must be called before swap_free().
> + */
> + arch_swap_restore(entry, folio);
> +
> /*
> * Remove the swap entry and conditionally try to free up the swapcache.
> * We're already holding a reference on the page but haven't mapped it

2023-05-19 16:46:59

by Catalin Marinas

Subject: Re: [PATCH v3 1/3] mm: Call arch_swap_restore() from do_swap_page()

On Tue, May 16, 2023 at 07:21:11PM -0700, Peter Collingbourne wrote:
> Commit c145e0b47c77 ("mm: streamline COW logic in do_swap_page()") moved
> the call to swap_free() before the call to set_pte_at(), which meant that
> the MTE tags could end up being freed before set_pte_at() had a chance
> to restore them. Fix it by adding a call to the arch_swap_restore() hook
> before the call to swap_free().
>
> Signed-off-by: Peter Collingbourne <[email protected]>
> Link: https://linux-review.googlesource.com/id/I6470efa669e8bd2f841049b8c61020c510678965
> Cc: <[email protected]> # 6.1
> Fixes: c145e0b47c77 ("mm: streamline COW logic in do_swap_page()")
> Reported-by: Qun-wei Lin (林群崴) <[email protected]>
> Closes: https://lore.kernel.org/all/[email protected]/

Acked-by: Catalin Marinas <[email protected]>