When the kernel copy a page from ksm_might_need_to_copy(), but runs
into an uncorrectable error, it will crash since poisoned page is
consumed by kernel, this is similar to Copy-on-write poison recovery,
When an error is detected during the page copy, return VM_FAULT_HWPOISON,
which help us to avoid system crash. Note, memory failure on a KSM
page will be skipped, but still call memory_failure_queue() to be
consistent with general memory failure process.

Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
v2: fix type error

 mm/ksm.c      | 8 ++++++--
 mm/memory.c   | 3 +++
 mm/swapfile.c | 2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index dd02780c387f..83e2f74ae7da 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
 		new_page = NULL;
 	}
 	if (new_page) {
-		copy_user_highpage(new_page, page, address, vma);
-
+		if (copy_mc_user_highpage(new_page, page, address, vma)) {
+			put_page(new_page);
+			new_page = ERR_PTR(-EHWPOISON);
+			memory_failure_queue(page_to_pfn(page), 0);
+			return new_page;
+		}
 		SetPageDirty(new_page);
 		__SetPageUptodate(new_page);
 		__SetPageLocked(new_page);
diff --git a/mm/memory.c b/mm/memory.c
index aad226daf41b..5b2c137dfb2a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		if (unlikely(!page)) {
 			ret = VM_FAULT_OOM;
 			goto out_page;
+		} else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
+			ret = VM_FAULT_HWPOISON;
+			goto out_page;
 		}
 		folio = page_folio(page);
 
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 908a529bca12..d479811bc311 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
 
 	swapcache = page;
 	page = ksm_might_need_to_copy(page, vma, addr);
-	if (unlikely(!page))
+	if (IS_ERR_OR_NULL(page))
 		return -ENOMEM;
 
 	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
-- 
2.35.3

On 2022/12/9 15:28, Kefeng Wang wrote:
> When the kernel copy a page from ksm_might_need_to_copy(), but runs
> into an uncorrectable error, it will crash since poisoned page is
> consumed by kernel, this is similar to Copy-on-write poison recovery,
> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
> which help us to avoid system crash. Note, memory failure on a KSM
> page will be skipped, but still call memory_failure_queue() to be
> consistent with general memory failure process.

Thanks for your patch.

> 
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> ---
> v2: fix type error
> 
>  mm/ksm.c      | 8 ++++++--
>  mm/memory.c   | 3 +++
>  mm/swapfile.c | 2 +-
>  3 files changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/mm/ksm.c b/mm/ksm.c
> index dd02780c387f..83e2f74ae7da 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -2629,8 +2629,12 @@ struct page *ksm_might_need_to_copy(struct page *page,
>  		new_page = NULL;
>  	}
>  	if (new_page) {
> -		copy_user_highpage(new_page, page, address, vma);
> -
> +		if (copy_mc_user_highpage(new_page, page, address, vma)) {
> +			put_page(new_page);
> +			new_page = ERR_PTR(-EHWPOISON);
> +			memory_failure_queue(page_to_pfn(page), 0);
> +			return new_page;
> +		}
>  		SetPageDirty(new_page);
>  		__SetPageUptodate(new_page);
>  		__SetPageLocked(new_page);
> diff --git a/mm/memory.c b/mm/memory.c
> index aad226daf41b..5b2c137dfb2a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3840,6 +3840,9 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
>  		if (unlikely(!page)) {
>  			ret = VM_FAULT_OOM;
>  			goto out_page;
> +		} else if (unlikely(PTR_ERR(page) == -EHWPOISON)) {
> +			ret = VM_FAULT_HWPOISON;
> +			goto out_page;
>  		}
>  		folio = page_folio(page);
>  
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 908a529bca12..d479811bc311 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>  
>  	swapcache = page;
>  	page = ksm_might_need_to_copy(page, vma, addr);
> -	if (unlikely(!page))
> +	if (IS_ERR_OR_NULL(page))

IMHO, it might be better to install a hwpoison entry here. Or later swapoff ops will trigger
the uncorrectable error again?

Thanks,
Miaohe Lin

On 2022/12/12 10:36, Miaohe Lin wrote:
> On 2022/12/9 15:28, Kefeng Wang wrote:
>> When the kernel copy a page from ksm_might_need_to_copy(), but runs
>> into an uncorrectable error, it will crash since poisoned page is
>> consumed by kernel, this is similar to Copy-on-write poison recovery,
>> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
>> which help us to avoid system crash. Note, memory failure on a KSM
>> page will be skipped, but still call memory_failure_queue() to be
>> consistent with general memory failure process.
...
>   
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 908a529bca12..d479811bc311 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -1767,7 +1767,7 @@ static int unuse_pte(struct vm_area_struct *vma, pmd_t *pmd,
>   
>   	swapcache = page;
>   	page = ksm_might_need_to_copy(page, vma, addr);
> -	if (unlikely(!page))
> +	if (IS_ERR_OR_NULL(page))
> IMHO, it might be better to install a hwpoison entry here. Or later swapoff ops will trigger
> the uncorrectable error again?
Thanks for you suggestion, will do in v3.
> Thanks,
> Miaohe Lin
>

On Fri, 9 Dec 2022 15:28:01 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:

> When the kernel copy a page from ksm_might_need_to_copy(), but runs
> into an uncorrectable error, it will crash since poisoned page is
> consumed by kernel, this is similar to Copy-on-write poison recovery,
> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
> which help us to avoid system crash. Note, memory failure on a KSM
> page will be skipped, but still call memory_failure_queue() to be
> consistent with general memory failure process.

Thanks.  Sorry, lots of paperwork and bureaucracy:


Is a copy of the oops(?) output available?

Did someone else report this?  If so, is a Reported-by available for
that?  And a Link: for the Reported-by:, which is a coming thing.

Can we identify a Fixes: target?

Is a cc:stable appropriate?

On 2022/12/10 8:50, Andrew Morton wrote:
> On Fri, 9 Dec 2022 15:28:01 +0800 Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>
>> When the kernel copy a page from ksm_might_need_to_copy(), but runs
>> into an uncorrectable error, it will crash since poisoned page is
>> consumed by kernel, this is similar to Copy-on-write poison recovery,
>> When an error is detected during the page copy, return VM_FAULT_HWPOISON,
>> which help us to avoid system crash. Note, memory failure on a KSM
>> page will be skipped, but still call memory_failure_queue() to be
>> consistent with general memory failure process.
> Thanks.  Sorry, lots of paperwork and bureaucracy:
>
>
> Is a copy of the oops(?) output available?
>
> Did someone else report this?  If so, is a Reported-by available for
> that?  And a Link: for the Reported-by:, which is a coming thing.
>
> Can we identify a Fixes: target?
>
> Is a cc:stable appropriate?
We are trying to support ARCH_HAS_COPY_MC on arm64[1] and trying to 
recover from CoW faults[2],
also tony do the same thing(recover from CoW) on X86[3]. The kernel copy 
in ksm_might_need_to_copy()
could recover, this is an enhance of COPY_MC, so I think no need to add 
Fixes and stable.

Thanks.

[1] 
https://lore.kernel.org/linux-arm-kernel/20220812070557.1028499-1-tongtiangen@huawei.com/
[2] 
https://lore.kernel.org/linux-arm-kernel/20220812070557.1028499-5-tongtiangen@huawei.com/
[3] 
https://lore.kernel.org/lkml/20221031201029.102123-2-tony.luck@intel.com/


>