* [PATCH] mm: do not access page->mapping directly on page_endio @ 2017-02-22 5:39 Minchan Kim 2017-02-22 12:11 ` Michal Hocko 0 siblings, 1 reply; 6+ messages in thread From: Minchan Kim @ 2017-02-22 5:39 UTC (permalink / raw) To: Andrew Morton Cc: linux-kernel, kernel-team, Minchan Kim, Matthew Wilcox, stable With rw_page, page_endio is used for completing IO on a page and it propagates write error to the address space if the IO fails. The problem is it accesses page->mapping directly which might be okay for file-backed pages but it shouldn't for anonymous page. Otherwise, it can corrupt one of field from anon_vma under us and system goes panic randomly. Cc: Matthew Wilcox <willy@infradead.org> Cc: <stable@vger.kernel.org> Signed-off-by: Minchan Kim <minchan@kernel.org> --- mm/filemap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 2ba46f410c7c..1944c631e3e6 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err) unlock_page(page); } else { if (err) { + struct address_space *mapping; + SetPageError(page); - if (page->mapping) - mapping_set_error(page->mapping, err); + mapping = page_mapping(page); + if (mapping) + mapping_set_error(mapping, err); } end_page_writeback(page); } -- 2.7.4 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: do not access page->mapping directly on page_endio 2017-02-22 5:39 [PATCH] mm: do not access page->mapping directly on page_endio Minchan Kim @ 2017-02-22 12:11 ` Michal Hocko 2017-02-22 14:35 ` Minchan Kim 0 siblings, 1 reply; 6+ messages in thread From: Michal Hocko @ 2017-02-22 12:11 UTC (permalink / raw) To: Minchan Kim Cc: Andrew Morton, linux-kernel, kernel-team, Matthew Wilcox, stable On Wed 22-02-17 14:39:24, Minchan Kim wrote: > With rw_page, page_endio is used for completing IO on a page > and it propagates write error to the address space if the IO > fails. The problem is it accesses page->mapping directly which > might be okay for file-backed pages but it shouldn't for > anonymous page. Otherwise, it can corrupt one of field from > anon_vma under us and system goes panic randomly. I was about to say that anonymous pages shouldn't hit that path because the end_swap_bio_write doesn call page_endio. But then I've noticed that zram does call this function. On a closer look, though, it doesn't seem to call it with err != 0 so it cannot hit this path. So I am wondering whether this actually fixes anything. Why it has been marked for stable? > > Cc: Matthew Wilcox <willy@infradead.org> > Cc: <stable@vger.kernel.org> > Signed-off-by: Minchan Kim <minchan@kernel.org> > --- > mm/filemap.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 2ba46f410c7c..1944c631e3e6 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err) > unlock_page(page); > } else { > if (err) { > + struct address_space *mapping; > + > SetPageError(page); > - if (page->mapping) > - mapping_set_error(page->mapping, err); > + mapping = page_mapping(page); > + if (mapping) > + mapping_set_error(mapping, err); > } > end_page_writeback(page); > } > -- > 2.7.4 -- Michal Hocko SUSE Labs ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: do not access page->mapping directly on page_endio 2017-02-22 12:11 ` Michal Hocko @ 2017-02-22 14:35 ` Minchan Kim 2017-02-22 14:53 ` Michal Hocko 0 siblings, 1 reply; 6+ messages in thread From: Minchan Kim @ 2017-02-22 14:35 UTC (permalink / raw) To: Michal Hocko Cc: Andrew Morton, linux-kernel, kernel-team, Matthew Wilcox, stable On Wed, Feb 22, 2017 at 01:11:00PM +0100, Michal Hocko wrote: > On Wed 22-02-17 14:39:24, Minchan Kim wrote: > > With rw_page, page_endio is used for completing IO on a page > > and it propagates write error to the address space if the IO > > fails. The problem is it accesses page->mapping directly which > > might be okay for file-backed pages but it shouldn't for > > anonymous page. Otherwise, it can corrupt one of field from > > anon_vma under us and system goes panic randomly. > > I was about to say that anonymous pages shouldn't hit that path because > the end_swap_bio_write doesn call page_endio. But then I've noticed that No. For driver to support rw_page, every swap_writepage calls rw_page. swap_writepage bdev_writepage ops->rw_page > zram does call this function. On a closer look, though, it doesn't seem > to call it with err != 0 so it cannot hit this path. So I am wondering > whether this actually fixes anything. Why it has been marked for stable? Look at other drivers to support rw_page, not zram, esp, brd. They can be used for swap device and then can hit the case. In fact, I encountered the BUG during zram development(i.e., it doesn't land to upstream) and it was really hard to figure it out because it made random crash, sometime mmap_sem lockdep, sometime other places where places never related to zram/zsmalloc, sometime not reproducible. When I consider how that bug is subtle and people do fast-swap test as brd, it's worth to add stable mark, I think. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: do not access page->mapping directly on page_endio 2017-02-22 14:35 ` Minchan Kim @ 2017-02-22 14:53 ` Michal Hocko 2017-02-23 23:26 ` Minchan Kim 0 siblings, 1 reply; 6+ messages in thread From: Michal Hocko @ 2017-02-22 14:53 UTC (permalink / raw) To: Minchan Kim Cc: Andrew Morton, linux-kernel, kernel-team, Matthew Wilcox, stable On Wed 22-02-17 23:35:17, Minchan Kim wrote: > On Wed, Feb 22, 2017 at 01:11:00PM +0100, Michal Hocko wrote: > > On Wed 22-02-17 14:39:24, Minchan Kim wrote: > > > With rw_page, page_endio is used for completing IO on a page > > > and it propagates write error to the address space if the IO > > > fails. The problem is it accesses page->mapping directly which > > > might be okay for file-backed pages but it shouldn't for > > > anonymous page. Otherwise, it can corrupt one of field from > > > anon_vma under us and system goes panic randomly. > > > > I was about to say that anonymous pages shouldn't hit that path because > > the end_swap_bio_write doesn call page_endio. But then I've noticed that > > No. For driver to support rw_page, every swap_writepage calls rw_page. > > swap_writepage > bdev_writepage > ops->rw_page Ohh, you are right, I have missed this option. I was looking at the normal swapout path which uses bio. > > zram does call this function. On a closer look, though, it doesn't seem > > to call it with err != 0 so it cannot hit this path. So I am wondering > > whether this actually fixes anything. Why it has been marked for stable? > > Look at other drivers to support rw_page, not zram, esp, brd. > They can be used for swap device and then can hit the case. > > In fact, I encountered the BUG during zram development(i.e., it doesn't > land to upstream) and it was really hard to figure it out because it made > random crash, sometime mmap_sem lockdep, sometime other places where > places never related to zram/zsmalloc, sometime not reproducible. > > When I consider how that bug is subtle and people do fast-swap test as brd, > it's worth to add stable mark, I think. Sure, could you add this to the changelog. Along with Fixes tag? I suspect it is dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()") which has introduced this but I didn't look too close. The patch is trivially correct. -- Michal Hocko SUSE Labs ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: do not access page->mapping directly on page_endio 2017-02-22 14:53 ` Michal Hocko @ 2017-02-23 23:26 ` Minchan Kim 2017-02-24 9:13 ` Michal Hocko 0 siblings, 1 reply; 6+ messages in thread From: Minchan Kim @ 2017-02-23 23:26 UTC (permalink / raw) To: Michal Hocko Cc: Andrew Morton, linux-kernel, kernel-team, Matthew Wilcox, stable On Wed, Feb 22, 2017 at 03:53:16PM +0100, Michal Hocko wrote: > On Wed 22-02-17 23:35:17, Minchan Kim wrote: > > On Wed, Feb 22, 2017 at 01:11:00PM +0100, Michal Hocko wrote: > > > On Wed 22-02-17 14:39:24, Minchan Kim wrote: > > > > With rw_page, page_endio is used for completing IO on a page > > > > and it propagates write error to the address space if the IO > > > > fails. The problem is it accesses page->mapping directly which > > > > might be okay for file-backed pages but it shouldn't for > > > > anonymous page. Otherwise, it can corrupt one of field from > > > > anon_vma under us and system goes panic randomly. > > > > > > I was about to say that anonymous pages shouldn't hit that path because > > > the end_swap_bio_write doesn call page_endio. But then I've noticed that > > > > No. For driver to support rw_page, every swap_writepage calls rw_page. > > > > swap_writepage > > bdev_writepage > > ops->rw_page > > Ohh, you are right, I have missed this option. I was looking at the > normal swapout path which uses bio. > > > > zram does call this function. On a closer look, though, it doesn't seem > > > to call it with err != 0 so it cannot hit this path. So I am wondering > > > whether this actually fixes anything. Why it has been marked for stable? > > > > Look at other drivers to support rw_page, not zram, esp, brd. > > They can be used for swap device and then can hit the case. > > > > In fact, I encountered the BUG during zram development(i.e., it doesn't > > land to upstream) and it was really hard to figure it out because it made > > random crash, sometime mmap_sem lockdep, sometime other places where > > places never related to zram/zsmalloc, sometime not reproducible. > > > > When I consider how that bug is subtle and people do fast-swap test as brd, > > it's worth to add stable mark, I think. > > Sure, could you add this to the changelog. Along with Fixes tag? I > suspect it is dd6bd0d9c7db ("swap: use bdev_read_page() / > bdev_write_page()") which has introduced this but I didn't look too > close. The patch is trivially correct. Sure. Thanks for the review. Andrew, Could you change description with this? >From 9efb87a873db67a9e6ebf44fdabf7d05fe4b4e21 Mon Sep 17 00:00:00 2001 From: Minchan Kim <minchan@kernel.org> Date: Fri, 4 Nov 2016 09:12:39 +0900 Subject: [PATCH v2] mm: do not access page->mapping directly on page_endio With rw_page, page_endio is used for completing IO on a page and it propagates write error to the address space if the IO fails. The problem is it accesses page->mapping directly which might be okay for file-backed pages but it shouldn't for anonymous page. Otherwise, it can corrupt one of field from anon_vma under us and system goes panic randomly. swap_writepage bdev_writepage ops->rw_page I encountered the BUG during developing new zram feature and it was really hard to figure it out because it made random crash, somtime mmap_sem lockdep, sometime other places where places never related to zram/zsmalloc, and not reproducible with some configuration. When I consider how that bug is subtle and people do fast-swap test with brd, it's worth to add stable mark, I think. Fixes: dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()") Cc: Michal Hocko <mhocko@kernel.org> Cc: Matthew Wilcox <willy@infradead.org> Cc: <stable@vger.kernel.org> Signed-off-by: Minchan Kim <minchan@kernel.org> --- * from v1 * add more detailed description with Fix tag - Michal mm/filemap.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index 2ba46f410c7c..1944c631e3e6 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err) unlock_page(page); } else { if (err) { + struct address_space *mapping; + SetPageError(page); - if (page->mapping) - mapping_set_error(page->mapping, err); + mapping = page_mapping(page); + if (mapping) + mapping_set_error(mapping, err); } end_page_writeback(page); } -- 2.7.4 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] mm: do not access page->mapping directly on page_endio 2017-02-23 23:26 ` Minchan Kim @ 2017-02-24 9:13 ` Michal Hocko 0 siblings, 0 replies; 6+ messages in thread From: Michal Hocko @ 2017-02-24 9:13 UTC (permalink / raw) To: Minchan Kim Cc: Andrew Morton, linux-kernel, kernel-team, Matthew Wilcox, stable On Fri 24-02-17 08:26:09, Minchan Kim wrote: [...] > >From 9efb87a873db67a9e6ebf44fdabf7d05fe4b4e21 Mon Sep 17 00:00:00 2001 > From: Minchan Kim <minchan@kernel.org> > Date: Fri, 4 Nov 2016 09:12:39 +0900 > Subject: [PATCH v2] mm: do not access page->mapping directly on page_endio > > With rw_page, page_endio is used for completing IO on a page > and it propagates write error to the address space if the IO > fails. The problem is it accesses page->mapping directly which > might be okay for file-backed pages but it shouldn't for > anonymous page. Otherwise, it can corrupt one of field from > anon_vma under us and system goes panic randomly. > > swap_writepage > bdev_writepage > ops->rw_page > > I encountered the BUG during developing new zram feature and > it was really hard to figure it out because it made random > crash, somtime mmap_sem lockdep, sometime other places where > places never related to zram/zsmalloc, and not reproducible > with some configuration. > > When I consider how that bug is subtle and people do fast-swap > test with brd, it's worth to add stable mark, I think. > > Fixes: dd6bd0d9c7db ("swap: use bdev_read_page() / bdev_write_page()") > Cc: Michal Hocko <mhocko@kernel.org> > Cc: Matthew Wilcox <willy@infradead.org> > Cc: <stable@vger.kernel.org> > Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Michal Hocko <mhocko@suse.com> Thanks for the chagelog update > --- > * from v1 > * add more detailed description with Fix tag - Michal > > mm/filemap.c | 7 +++++-- > 1 file changed, 5 insertions(+), 2 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 2ba46f410c7c..1944c631e3e6 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -1008,9 +1008,12 @@ void page_endio(struct page *page, bool is_write, int err) > unlock_page(page); > } else { > if (err) { > + struct address_space *mapping; > + > SetPageError(page); > - if (page->mapping) > - mapping_set_error(page->mapping, err); > + mapping = page_mapping(page); > + if (mapping) > + mapping_set_error(mapping, err); > } > end_page_writeback(page); > } > -- > 2.7.4 -- Michal Hocko SUSE Labs ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2017-02-24 9:13 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2017-02-22 5:39 [PATCH] mm: do not access page->mapping directly on page_endio Minchan Kim 2017-02-22 12:11 ` Michal Hocko 2017-02-22 14:35 ` Minchan Kim 2017-02-22 14:53 ` Michal Hocko 2017-02-23 23:26 ` Minchan Kim 2017-02-24 9:13 ` Michal Hocko
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