* FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree
@ 2019-11-18 16:37 gregkh
2019-11-18 16:40 ` Greg KH
0 siblings, 1 reply; 5+ messages in thread
From: gregkh @ 2019-11-18 16:37 UTC (permalink / raw)
To: vinmenon, akpm, hughd, mhocko, minchan, minchan, stable, torvalds; +Cc: stable
The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 5df373e95689b9519b8557da7c5bd0db0856d776 Mon Sep 17 00:00:00 2001
From: Vinayak Menon <vinmenon@codeaurora.org>
Date: Fri, 15 Nov 2019 17:35:00 -0800
Subject: [PATCH] mm/page_io.c: do not free shared swap slots
The following race is observed due to which a processes faulting on a
swap entry, finds the page neither in swapcache nor swap. This causes
zram to give a zero filled page that gets mapped to the process,
resulting in a user space crash later.
Consider parent and child processes Pa and Pb sharing the same swap slot
with swap_count 2. Swap is on zram with SWP_SYNCHRONOUS_IO set.
Virtual address 'VA' of Pa and Pb points to the shared swap entry.
Pa Pb
fault on VA fault on VA
do_swap_page do_swap_page
lookup_swap_cache fails lookup_swap_cache fails
Pb scheduled out
swapin_readahead (deletes zram entry)
swap_free (makes swap_count 1)
Pb scheduled in
swap_readpage (swap_count == 1)
Takes SWP_SYNCHRONOUS_IO path
zram enrty absent
zram gives a zero filled page
Fix this by making sure that swap slot is freed only when swap count
drops down to one.
Link: http://lkml.kernel.org/r/1571743294-14285-1-git-send-email-vinmenon@codeaurora.org
Fixes: aa8d22a11da9 ("mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference")
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Suggested-by: Minchan Kim <minchan@google.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page_io.c b/mm/page_io.c
index 24ee600f9131..60a66a58b9bf 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -73,6 +73,7 @@ static void swap_slot_free_notify(struct page *page)
{
struct swap_info_struct *sis;
struct gendisk *disk;
+ swp_entry_t entry;
/*
* There is no guarantee that the page is in swap cache - the software
@@ -104,11 +105,10 @@ static void swap_slot_free_notify(struct page *page)
* we again wish to reclaim it.
*/
disk = sis->bdev->bd_disk;
- if (disk->fops->swap_slot_free_notify) {
- swp_entry_t entry;
+ entry.val = page_private(page);
+ if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
unsigned long offset;
- entry.val = page_private(page);
offset = swp_offset(entry);
SetPageDirty(page);
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree
2019-11-18 16:37 FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree gregkh
@ 2019-11-18 16:40 ` Greg KH
2019-11-19 10:57 ` Vinayak Menon
0 siblings, 1 reply; 5+ messages in thread
From: Greg KH @ 2019-11-18 16:40 UTC (permalink / raw)
To: vinmenon, akpm, hughd, mhocko, minchan, minchan, stable, torvalds
On Mon, Nov 18, 2019 at 05:37:16PM +0100, gregkh@linuxfoundation.org wrote:
>
> The patch below does not apply to the 4.19-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
Note, this applies, but just breaks the build, so it needs a backport
for 4.19 if people want to see it there.
thanks,
greg k-h
> ------------------ original commit in Linus's tree ------------------
>
> >From 5df373e95689b9519b8557da7c5bd0db0856d776 Mon Sep 17 00:00:00 2001
> From: Vinayak Menon <vinmenon@codeaurora.org>
> Date: Fri, 15 Nov 2019 17:35:00 -0800
> Subject: [PATCH] mm/page_io.c: do not free shared swap slots
>
> The following race is observed due to which a processes faulting on a
> swap entry, finds the page neither in swapcache nor swap. This causes
> zram to give a zero filled page that gets mapped to the process,
> resulting in a user space crash later.
>
> Consider parent and child processes Pa and Pb sharing the same swap slot
> with swap_count 2. Swap is on zram with SWP_SYNCHRONOUS_IO set.
> Virtual address 'VA' of Pa and Pb points to the shared swap entry.
>
> Pa Pb
>
> fault on VA fault on VA
> do_swap_page do_swap_page
> lookup_swap_cache fails lookup_swap_cache fails
> Pb scheduled out
> swapin_readahead (deletes zram entry)
> swap_free (makes swap_count 1)
> Pb scheduled in
> swap_readpage (swap_count == 1)
> Takes SWP_SYNCHRONOUS_IO path
> zram enrty absent
> zram gives a zero filled page
>
> Fix this by making sure that swap slot is freed only when swap count
> drops down to one.
>
> Link: http://lkml.kernel.org/r/1571743294-14285-1-git-send-email-vinmenon@codeaurora.org
> Fixes: aa8d22a11da9 ("mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference")
> Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
> Suggested-by: Minchan Kim <minchan@google.com>
> Acked-by: Minchan Kim <minchan@kernel.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>
> diff --git a/mm/page_io.c b/mm/page_io.c
> index 24ee600f9131..60a66a58b9bf 100644
> --- a/mm/page_io.c
> +++ b/mm/page_io.c
> @@ -73,6 +73,7 @@ static void swap_slot_free_notify(struct page *page)
> {
> struct swap_info_struct *sis;
> struct gendisk *disk;
> + swp_entry_t entry;
>
> /*
> * There is no guarantee that the page is in swap cache - the software
> @@ -104,11 +105,10 @@ static void swap_slot_free_notify(struct page *page)
> * we again wish to reclaim it.
> */
> disk = sis->bdev->bd_disk;
> - if (disk->fops->swap_slot_free_notify) {
> - swp_entry_t entry;
> + entry.val = page_private(page);
> + if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
> unsigned long offset;
>
> - entry.val = page_private(page);
> offset = swp_offset(entry);
>
> SetPageDirty(page);
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree
2019-11-18 16:40 ` Greg KH
@ 2019-11-19 10:57 ` Vinayak Menon
2019-11-21 20:34 ` Greg KH
2019-11-25 16:43 ` Sasha Levin
0 siblings, 2 replies; 5+ messages in thread
From: Vinayak Menon @ 2019-11-19 10:57 UTC (permalink / raw)
To: Greg KH, akpm, hughd, mhocko, minchan, minchan, stable, torvalds
On 11/18/2019 10:10 PM, Greg KH wrote:
> On Mon, Nov 18, 2019 at 05:37:16PM +0100, gregkh@linuxfoundation.org wrote:
>> The patch below does not apply to the 4.19-stable tree.
>> If someone wants it applied there, or to any other stable or longterm
>> tree, then please email the backport, including the original git commit
>> id to <stable@vger.kernel.org>.
> Note, this applies, but just breaks the build, so it needs a backport
> for 4.19 if people want to see it there.
The version below fixes the build on 4.19.
>
> thanks,
>
> greg k-h
From 3745cc4bb5cddbc1058889e4f779492060d5e550 Mon Sep 17 00:00:00 2001
From: Vinayak Menon <vinmenon@codeaurora.org>
Date: Fri, 15 Nov 2019 17:35:00 -0800
Subject: [PATCH] mm/page_io.c: do not free shared swap slots
commit 5df373e95689b9519b8557da7c5bd0db0856d776 upstream.
The following race is observed due to which a processes faulting on a
swap entry, finds the page neither in swapcache nor swap. This causes
zram to give a zero filled page that gets mapped to the process,
resulting in a user space crash later.
Consider parent and child processes Pa and Pb sharing the same swap slot
with swap_count 2. Swap is on zram with SWP_SYNCHRONOUS_IO set.
Virtual address 'VA' of Pa and Pb points to the shared swap entry.
Pa Pb
fault on VA fault on VA
do_swap_page do_swap_page
lookup_swap_cache fails lookup_swap_cache fails
Pb scheduled out
swapin_readahead (deletes zram entry)
swap_free (makes swap_count 1)
Pb scheduled in
swap_readpage (swap_count == 1)
Takes SWP_SYNCHRONOUS_IO path
zram enrty absent
zram gives a zero filled page
Fix this by making sure that swap slot is freed only when swap count
drops down to one.
Link: http://lkml.kernel.org/r/1571743294-14285-1-git-send-email-vinmenon@codeaurora.org
Fixes: aa8d22a11da9 ("mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference")
Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Suggested-by: Minchan Kim <minchan@google.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
mm/page_io.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/mm/page_io.c b/mm/page_io.c
index abc1466..e763047 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -77,6 +77,7 @@ static void swap_slot_free_notify(struct page *page)
{
struct swap_info_struct *sis;
struct gendisk *disk;
+ swp_entry_t entry;
/*
* There is no guarantee that the page is in swap cache - the software
@@ -108,11 +109,11 @@ static void swap_slot_free_notify(struct page *page)
* we again wish to reclaim it.
*/
disk = sis->bdev->bd_disk;
- if (disk->fops->swap_slot_free_notify) {
- swp_entry_t entry;
+ entry.val = page_private(page);
+ if (disk->fops->swap_slot_free_notify &&
+ __swap_count(sis, entry) == 1) {
unsigned long offset;
- entry.val = page_private(page);
offset = swp_offset(entry);
SetPageDirty(page);
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation
>
>> ------------------ original commit in Linus's tree ------------------
>>
>> >From 5df373e95689b9519b8557da7c5bd0db0856d776 Mon Sep 17 00:00:00 2001
>> From: Vinayak Menon <vinmenon@codeaurora.org>
>> Date: Fri, 15 Nov 2019 17:35:00 -0800
>> Subject: [PATCH] mm/page_io.c: do not free shared swap slots
>>
>> The following race is observed due to which a processes faulting on a
>> swap entry, finds the page neither in swapcache nor swap. This causes
>> zram to give a zero filled page that gets mapped to the process,
>> resulting in a user space crash later.
>>
>> Consider parent and child processes Pa and Pb sharing the same swap slot
>> with swap_count 2. Swap is on zram with SWP_SYNCHRONOUS_IO set.
>> Virtual address 'VA' of Pa and Pb points to the shared swap entry.
>>
>> Pa Pb
>>
>> fault on VA fault on VA
>> do_swap_page do_swap_page
>> lookup_swap_cache fails lookup_swap_cache fails
>> Pb scheduled out
>> swapin_readahead (deletes zram entry)
>> swap_free (makes swap_count 1)
>> Pb scheduled in
>> swap_readpage (swap_count == 1)
>> Takes SWP_SYNCHRONOUS_IO path
>> zram enrty absent
>> zram gives a zero filled page
>>
>> Fix this by making sure that swap slot is freed only when swap count
>> drops down to one.
>>
>> Link: http://lkml.kernel.org/r/1571743294-14285-1-git-send-email-vinmenon@codeaurora.org
>> Fixes: aa8d22a11da9 ("mm: swap: SWP_SYNCHRONOUS_IO: skip swapcache only if swapped page has no other reference")
>> Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
>> Suggested-by: Minchan Kim <minchan@google.com>
>> Acked-by: Minchan Kim <minchan@kernel.org>
>> Cc: Michal Hocko <mhocko@suse.com>
>> Cc: Hugh Dickins <hughd@google.com>
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
>> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
>>
>> diff --git a/mm/page_io.c b/mm/page_io.c
>> index 24ee600f9131..60a66a58b9bf 100644
>> --- a/mm/page_io.c
>> +++ b/mm/page_io.c
>> @@ -73,6 +73,7 @@ static void swap_slot_free_notify(struct page *page)
>> {
>> struct swap_info_struct *sis;
>> struct gendisk *disk;
>> + swp_entry_t entry;
>>
>> /*
>> * There is no guarantee that the page is in swap cache - the software
>> @@ -104,11 +105,10 @@ static void swap_slot_free_notify(struct page *page)
>> * we again wish to reclaim it.
>> */
>> disk = sis->bdev->bd_disk;
>> - if (disk->fops->swap_slot_free_notify) {
>> - swp_entry_t entry;
>> + entry.val = page_private(page);
>> + if (disk->fops->swap_slot_free_notify && __swap_count(entry) == 1) {
>> unsigned long offset;
>>
>> - entry.val = page_private(page);
>> offset = swp_offset(entry);
>>
>> SetPageDirty(page);
>>
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree
2019-11-19 10:57 ` Vinayak Menon
@ 2019-11-21 20:34 ` Greg KH
2019-11-25 16:43 ` Sasha Levin
1 sibling, 0 replies; 5+ messages in thread
From: Greg KH @ 2019-11-21 20:34 UTC (permalink / raw)
To: Vinayak Menon; +Cc: akpm, hughd, mhocko, minchan, minchan, stable, torvalds
On Tue, Nov 19, 2019 at 10:57:13AM +0000, Vinayak Menon wrote:
>
> On 11/18/2019 10:10 PM, Greg KH wrote:
> > On Mon, Nov 18, 2019 at 05:37:16PM +0100, gregkh@linuxfoundation.org wrote:
> >> The patch below does not apply to the 4.19-stable tree.
> >> If someone wants it applied there, or to any other stable or longterm
> >> tree, then please email the backport, including the original git commit
> >> id to <stable@vger.kernel.org>.
> > Note, this applies, but just breaks the build, so it needs a backport
> > for 4.19 if people want to see it there.
>
> The version below fixes the build on 4.19.
The patch you sent was totally corrupted, I couldn't figure out how to
fix it up. Please resend it in a format I can apply it in.
thanks,
greg k-h
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree
2019-11-19 10:57 ` Vinayak Menon
2019-11-21 20:34 ` Greg KH
@ 2019-11-25 16:43 ` Sasha Levin
1 sibling, 0 replies; 5+ messages in thread
From: Sasha Levin @ 2019-11-25 16:43 UTC (permalink / raw)
To: Vinayak Menon
Cc: Greg KH, akpm, hughd, mhocko, minchan, minchan, stable, torvalds
On Tue, Nov 19, 2019 at 10:57:13AM +0000, Vinayak Menon wrote:
>
>On 11/18/2019 10:10 PM, Greg KH wrote:
>> On Mon, Nov 18, 2019 at 05:37:16PM +0100, gregkh@linuxfoundation.org wrote:
>>> The patch below does not apply to the 4.19-stable tree.
>>> If someone wants it applied there, or to any other stable or longterm
>>> tree, then please email the backport, including the original git commit
>>> id to <stable@vger.kernel.org>.
>> Note, this applies, but just breaks the build, so it needs a backport
>> for 4.19 if people want to see it there.
>
>The version below fixes the build on 4.19.
I've fixed it up based on the version sent by Vinayak and queued it up
for 4.19.
--
Thanks,
Sasha
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2019-11-25 16:43 UTC | newest]
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2019-11-18 16:37 FAILED: patch "[PATCH] mm/page_io.c: do not free shared swap slots" failed to apply to 4.19-stable tree gregkh
2019-11-18 16:40 ` Greg KH
2019-11-19 10:57 ` Vinayak Menon
2019-11-21 20:34 ` Greg KH
2019-11-25 16:43 ` Sasha Levin
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