linux-kernel - Re: BUG: Bad rss-counter state mm:ffff8800c5a96000 idx:3 val:3894

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Date:	Tue, 29 Dec 2015 10:30:37 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michal Hocko <mhocko@...nel.org>
Cc:	Jeremiah Mahler <jmmahler@...il.com>, linux-kernel@...r.kernel.org,
	Kees Cook <keescook@...omium.org>,
	Andy Lutomirski <luto@...capital.net>,
	Will Drewry <wad@...omium.org>, Ingo Molnar <mingo@...nel.org>,
	Tejun Heo <tj@...nel.org>
Subject: Re: BUG: Bad rss-counter state mm:ffff8800c5a96000 idx:3 val:3894

On Tue, 29 Dec 2015 17:23:47 +0100 Michal Hocko <mhocko@...nel.org> wrote:

> [CCing Andrew]
> 
> On Thu 24-12-15 09:12:53, Jeremiah Mahler wrote:
> > all,
> > 
> > I have started seeing a "Bad rss-counter" message in the logs with
> > the latest linux-next 20151222+.
> > 
> >   [  458.282192] BUG: Bad rss-counter state mm:ffff8800c5a96000 idx:3 val:3894
> 
> This is MM_SHMEMPAGES so an "unamapped" shmem memory. One possible
> reason might be an unitialized zap_details used from unmap_mapping_range
> during truncate introduced by "mm, oom: introduce oom reaper" from the
> mmotm tree. There is a fix for this which is still pending
> http://lkml.kernel.org/r/1450487091-7822-1-git-send-email-sasha.levin%40oracle.com

That won't be getting fixed until linux-next returns from holidays.

This:

--- a/mm/memory.c~mm-oom-introduce-oom-reaper-fix-5-fix
+++ a/mm/memory.c
@@ -2415,7 +2415,7 @@ static inline void unmap_mapping_range_t
 void unmap_mapping_range(struct address_space *mapping,
 		loff_t const holebegin, loff_t const holelen, int even_cows)
 {
-	struct zap_details details;
+	struct zap_details details = { };
 	pgoff_t hba = holebegin >> PAGE_SHIFT;
 	pgoff_t hlen = (holelen + PAGE_SIZE - 1) >> PAGE_SHIFT;
 
_

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