mm: cleancache: fix corruption on missed inode invalidation
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Message ID 20181112095734.17979-1-ptikhomirov@virtuozzo.com
State New
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Series
  • mm: cleancache: fix corruption on missed inode invalidation
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Commit Message

Pavel Tikhomirov Nov. 12, 2018, 9:57 a.m. UTC
If all pages are deleted from the mapping by memory reclaim and also
moved to the cleancache:

__delete_from_page_cache
  (no shadow case)
  unaccount_page_cache_page
    cleancache_put_page
  page_cache_delete
    mapping->nrpages -= nr
    (nrpages becomes 0)

We don't clean the cleancache for an inode after final file truncation
(removal).

truncate_inode_pages_final
  check (nrpages || nrexceptional) is false
    no truncate_inode_pages
      no cleancache_invalidate_inode(mapping)

These way when reading the new file created with same inode we may get
these trash leftover pages from cleancache and see wrong data instead of
the contents of the new file.

Fix it by always doing truncate_inode_pages which is already ready for
nrpages == 0 && nrexceptional == 0 case and just invalidates inode.

Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Vasily Averin <vvs@virtuozzo.com>
Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
---
 mm/truncate.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Jan Kara Nov. 12, 2018, 11:31 a.m. UTC | #1
On Mon 12-11-18 12:57:34, Pavel Tikhomirov wrote:
> If all pages are deleted from the mapping by memory reclaim and also
> moved to the cleancache:
> 
> __delete_from_page_cache
>   (no shadow case)
>   unaccount_page_cache_page
>     cleancache_put_page
>   page_cache_delete
>     mapping->nrpages -= nr
>     (nrpages becomes 0)
> 
> We don't clean the cleancache for an inode after final file truncation
> (removal).
> 
> truncate_inode_pages_final
>   check (nrpages || nrexceptional) is false
>     no truncate_inode_pages
>       no cleancache_invalidate_inode(mapping)
> 
> These way when reading the new file created with same inode we may get
> these trash leftover pages from cleancache and see wrong data instead of
> the contents of the new file.
> 
> Fix it by always doing truncate_inode_pages which is already ready for
> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
> 
> Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")
> To: Andrew Morton <akpm@linux-foundation.org>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Matthew Wilcox <willy@infradead.org>
> Cc: Andi Kleen <ak@linux.intel.com>
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Reviewed-by: Vasily Averin <vvs@virtuozzo.com>
> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
> ---
>  mm/truncate.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)

The patch looks good but can you add a short comment before the
truncate_inode_pages() call explaining why it needs to be called always?
Something like:

	 /*
	  * Cleancache needs notification even if there are no pages or
	  * shadow entries...
	  */

Otherwise you can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> 
> diff --git a/mm/truncate.c b/mm/truncate.c
> index 45d68e90b703..4c56c19e76eb 100644
> --- a/mm/truncate.c
> +++ b/mm/truncate.c
> @@ -517,9 +517,9 @@ void truncate_inode_pages_final(struct address_space *mapping)
>  		 */
>  		xa_lock_irq(&mapping->i_pages);
>  		xa_unlock_irq(&mapping->i_pages);
> -
> -		truncate_inode_pages(mapping, 0);
>  	}
> +
> +	truncate_inode_pages(mapping, 0);
>  }
>  EXPORT_SYMBOL(truncate_inode_pages_final);
>  
> -- 
> 2.17.1
>
Andrey Ryabinin Nov. 12, 2018, 11:40 a.m. UTC | #2
On 11/12/18 2:31 PM, Jan Kara wrote:
> On Mon 12-11-18 12:57:34, Pavel Tikhomirov wrote:
>> If all pages are deleted from the mapping by memory reclaim and also
>> moved to the cleancache:
>>
>> __delete_from_page_cache
>>   (no shadow case)
>>   unaccount_page_cache_page
>>     cleancache_put_page
>>   page_cache_delete
>>     mapping->nrpages -= nr
>>     (nrpages becomes 0)
>>
>> We don't clean the cleancache for an inode after final file truncation
>> (removal).
>>
>> truncate_inode_pages_final
>>   check (nrpages || nrexceptional) is false
>>     no truncate_inode_pages
>>       no cleancache_invalidate_inode(mapping)
>>
>> These way when reading the new file created with same inode we may get
>> these trash leftover pages from cleancache and see wrong data instead of
>> the contents of the new file.
>>
>> Fix it by always doing truncate_inode_pages which is already ready for
>> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
>>
>> Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")
>> To: Andrew Morton <akpm@linux-foundation.org>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Cc: Mel Gorman <mgorman@techsingularity.net>
>> Cc: Jan Kara <jack@suse.cz>
>> Cc: Matthew Wilcox <willy@infradead.org>
>> Cc: Andi Kleen <ak@linux.intel.com>
>> Cc: linux-mm@kvack.org
>> Cc: linux-kernel@vger.kernel.org
>> Reviewed-by: Vasily Averin <vvs@virtuozzo.com>
>> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
>> Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
>> ---
>>  mm/truncate.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> The patch looks good but can you add a short comment before the
> truncate_inode_pages() call explaining why it needs to be called always?
> Something like:
> 
> 	 /*
> 	  * Cleancache needs notification even if there are no pages or
> 	  * shadow entries...
> 	  */

Or we can just call cleancache_invalidate_inode(mapping) on else branch,
so the code would be more self-explanatory, and also avoid
function call in no-cleancache setups, which should the most of setups.
Jan Kara Nov. 12, 2018, 11:54 a.m. UTC | #3
On Mon 12-11-18 14:40:06, Andrey Ryabinin wrote:
> 
> 
> On 11/12/18 2:31 PM, Jan Kara wrote:
> > On Mon 12-11-18 12:57:34, Pavel Tikhomirov wrote:
> >> If all pages are deleted from the mapping by memory reclaim and also
> >> moved to the cleancache:
> >>
> >> __delete_from_page_cache
> >>   (no shadow case)
> >>   unaccount_page_cache_page
> >>     cleancache_put_page
> >>   page_cache_delete
> >>     mapping->nrpages -= nr
> >>     (nrpages becomes 0)
> >>
> >> We don't clean the cleancache for an inode after final file truncation
> >> (removal).
> >>
> >> truncate_inode_pages_final
> >>   check (nrpages || nrexceptional) is false
> >>     no truncate_inode_pages
> >>       no cleancache_invalidate_inode(mapping)
> >>
> >> These way when reading the new file created with same inode we may get
> >> these trash leftover pages from cleancache and see wrong data instead of
> >> the contents of the new file.
> >>
> >> Fix it by always doing truncate_inode_pages which is already ready for
> >> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
> >>
> >> Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")
> >> To: Andrew Morton <akpm@linux-foundation.org>
> >> Cc: Johannes Weiner <hannes@cmpxchg.org>
> >> Cc: Mel Gorman <mgorman@techsingularity.net>
> >> Cc: Jan Kara <jack@suse.cz>
> >> Cc: Matthew Wilcox <willy@infradead.org>
> >> Cc: Andi Kleen <ak@linux.intel.com>
> >> Cc: linux-mm@kvack.org
> >> Cc: linux-kernel@vger.kernel.org
> >> Reviewed-by: Vasily Averin <vvs@virtuozzo.com>
> >> Reviewed-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
> >> Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
> >> ---
> >>  mm/truncate.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > The patch looks good but can you add a short comment before the
> > truncate_inode_pages() call explaining why it needs to be called always?
> > Something like:
> > 
> > 	 /*
> > 	  * Cleancache needs notification even if there are no pages or
> > 	  * shadow entries...
> > 	  */
> 
> Or we can just call cleancache_invalidate_inode(mapping) on else branch,
> so the code would be more self-explanatory, and also avoid
> function call in no-cleancache setups, which should the most of setups.

That is workable for me as well although I'd be somewhat worried that if we
have calls to inform cleancache about final inode teardown in two different
places, they can get out of sync easily. So I somewhat prefer the current
solution + comment.

								Honza
Andrew Morton Nov. 15, 2018, 10:29 p.m. UTC | #4
On Mon, 12 Nov 2018 12:31:53 +0100 Jan Kara <jack@suse.cz> wrote:

> >  mm/truncate.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> The patch looks good but can you add a short comment before the
> truncate_inode_pages() call explaining why it needs to be called always?
> Something like:
> 
> 	 /*
> 	  * Cleancache needs notification even if there are no pages or
> 	  * shadow entries...
> 	  */

--- a/mm/truncate.c~mm-cleancache-fix-corruption-on-missed-inode-invalidation-fix
+++ a/mm/truncate.c
@@ -519,6 +519,10 @@ void truncate_inode_pages_final(struct a
 		xa_unlock_irq(&mapping->i_pages);
 	}
 
+	/*
+	 * Cleancache needs notification even if there are no pages or shadow
+	 * entries.
+	 */
 	truncate_inode_pages(mapping, 0);
 }
 EXPORT_SYMBOL(truncate_inode_pages_final);
Andrew Morton Nov. 15, 2018, 10:31 p.m. UTC | #5
On Mon, 12 Nov 2018 12:57:34 +0300 Pavel Tikhomirov <ptikhomirov@virtuozzo.com> wrote:

> If all pages are deleted from the mapping by memory reclaim and also
> moved to the cleancache:
> 
> __delete_from_page_cache
>   (no shadow case)
>   unaccount_page_cache_page
>     cleancache_put_page
>   page_cache_delete
>     mapping->nrpages -= nr
>     (nrpages becomes 0)
> 
> We don't clean the cleancache for an inode after final file truncation
> (removal).
> 
> truncate_inode_pages_final
>   check (nrpages || nrexceptional) is false
>     no truncate_inode_pages
>       no cleancache_invalidate_inode(mapping)
> 
> These way when reading the new file created with same inode we may get
> these trash leftover pages from cleancache and see wrong data instead of
> the contents of the new file.
> 
> Fix it by always doing truncate_inode_pages which is already ready for
> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
> 

Data corruption sounds serious.  Shouldn't we backport this into
-stable kernels?
Vasily Averin Nov. 16, 2018, 7:55 a.m. UTC | #6
On 11/16/18 1:31 AM, Andrew Morton wrote:
> On Mon, 12 Nov 2018 12:57:34 +0300 Pavel Tikhomirov <ptikhomirov@virtuozzo.com> wrote:
> 
>> If all pages are deleted from the mapping by memory reclaim and also
>> moved to the cleancache:
>>
>> __delete_from_page_cache
>>   (no shadow case)
>>   unaccount_page_cache_page
>>     cleancache_put_page
>>   page_cache_delete
>>     mapping->nrpages -= nr
>>     (nrpages becomes 0)
>>
>> We don't clean the cleancache for an inode after final file truncation
>> (removal).
>>
>> truncate_inode_pages_final
>>   check (nrpages || nrexceptional) is false
>>     no truncate_inode_pages
>>       no cleancache_invalidate_inode(mapping)
>>
>> These way when reading the new file created with same inode we may get
>> these trash leftover pages from cleancache and see wrong data instead of
>> the contents of the new file.
>>
>> Fix it by always doing truncate_inode_pages which is already ready for
>> nrpages == 0 && nrexceptional == 0 case and just invalidates inode.
>>
> 
> Data corruption sounds serious.  Shouldn't we backport this into
> -stable kernels?

Yes, it was broken in 4.14 kernel and it should affect all who uses cleancache
Fixes: commit 91b0abe36a7b ("mm + fs: store shadow entries in page cache")

Patch
diff mbox series

diff --git a/mm/truncate.c b/mm/truncate.c
index 45d68e90b703..4c56c19e76eb 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -517,9 +517,9 @@  void truncate_inode_pages_final(struct address_space *mapping)
 		 */
 		xa_lock_irq(&mapping->i_pages);
 		xa_unlock_irq(&mapping->i_pages);
-
-		truncate_inode_pages(mapping, 0);
 	}
+
+	truncate_inode_pages(mapping, 0);
 }
 EXPORT_SYMBOL(truncate_inode_pages_final);