From: Weijie Yang <weijie.yang@samsung.com>
Date: Wed, 29 Oct 2014 21:50:57 +0000 (-0700)
Subject: zram: avoid NULL pointer access in concurrent situation
X-Git-Tag: omap-for-v3.19/fixes-not-urgent-part1~39^2~2
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5a99e95b8d1cd47f6feddcdca6c71d22060df8a2;p=pandora-kernel.git

zram: avoid NULL pointer access in concurrent situation

There is a rare NULL pointer bug in mem_used_total_show() and
mem_used_max_store() in concurrent situation, like this:

zram is not initialized, process A is a mem_used_total reader which runs
periodically, while process B try to init zram.

	process A 				process B
  access meta, get a NULL value
						init zram, done
  init_done() is true
  access meta->mem_pool, get a NULL pointer BUG

This patch fixes this issue.

Signed-off-by: Weijie Yang <weijie.yang@samsung.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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