2023-07-01 08:05:16

by Miaohe Lin

Subject: [PATCH] mm: memory-failure: fix potential page refcnt leak in memory_failure()

put_ref_page() is not called to drop extra refcnt when comes from madvise
in the case pfn is valid but pgmap is NULL leading to page refcnt leak.

Fixes: 1e8aaedb182d ("mm,memory_failure: always pin the page in madvise_inject_error")
Signed-off-by: Miaohe Lin <[email protected]>
---
mm/memory-failure.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index e245191e6b04..65e2d4c5b50d 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2080,8 +2080,6 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
{
int rc = -ENXIO;

- put_ref_page(pfn, flags);
-
/* device metadata space is not recoverable */
if (!pgmap_pfn_valid(pgmap, pfn))
goto out;
@@ -2157,6 +2155,7 @@ int memory_failure(unsigned long pfn, int flags)

if (pfn_valid(pfn)) {
pgmap = get_dev_pagemap(pfn, NULL);
+ put_ref_page(pfn, flags);
if (pgmap) {
res = memory_failure_dev_pagemap(pfn, flags,
pgmap);
--
2.33.0

2023-07-03 07:13:55

by Naoya Horiguchi

Subject: Re: [PATCH] mm: memory-failure: fix potential page refcnt leak in memory_failure()

On Sat, Jul 01, 2023 at 03:28:37PM +0800, Miaohe Lin wrote:
> put_ref_page() is not called to drop extra refcnt when comes from madvise
> in the case pfn is valid but pgmap is NULL leading to page refcnt leak.

Is this test scenario realistic one? I don't think that we can call madvise() for
such a device memory page. If this is the case, this issue can be thought as
potentioal one (so no need to send to stable).

>
> Fixes: 1e8aaedb182d ("mm,memory_failure: always pin the page in madvise_inject_error")
> Signed-off-by: Miaohe Lin <[email protected]>

Anyway, the patch looks good to me. Thanks you.

Acked-by: Naoya Horiguchi <[email protected]>

> ---
> mm/memory-failure.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index e245191e6b04..65e2d4c5b50d 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -2080,8 +2080,6 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
> {
> int rc = -ENXIO;
>
> - put_ref_page(pfn, flags);
> -
> /* device metadata space is not recoverable */
> if (!pgmap_pfn_valid(pgmap, pfn))
> goto out;
> @@ -2157,6 +2155,7 @@ int memory_failure(unsigned long pfn, int flags)
>
> if (pfn_valid(pfn)) {
> pgmap = get_dev_pagemap(pfn, NULL);
> + put_ref_page(pfn, flags);
> if (pgmap) {
> res = memory_failure_dev_pagemap(pfn, flags,
> pgmap);
> --
> 2.33.0
>
>
>

2023-07-03 11:30:09

by Miaohe Lin

Subject: Re: [PATCH] mm: memory-failure: fix potential page refcnt leak in memory_failure()

On 2023/7/3 14:37, Naoya Horiguchi wrote:
> On Sat, Jul 01, 2023 at 03:28:37PM +0800, Miaohe Lin wrote:
>> put_ref_page() is not called to drop extra refcnt when comes from madvise
>> in the case pfn is valid but pgmap is NULL leading to page refcnt leak.
>
> Is this test scenario realistic one? I don't think that we can call madvise() for
> such a device memory page. If this is the case, this issue can be thought as
> potentioal one (so no need to send to stable).

This is a theoretical problem. If pagemap can ever be NULL after page refcnt is increased, this
would occur. I think it's not needed to send to stable too.

>
>>
>> Fixes: 1e8aaedb182d ("mm,memory_failure: always pin the page in madvise_inject_error")
>> Signed-off-by: Miaohe Lin <[email protected]>
>
> Anyway, the patch looks good to me. Thanks you.
>
> Acked-by: Naoya Horiguchi <[email protected]>

Thanks for your review and comment.