From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Date: Thu, 26 May 2011 23:25:52 +0000 (-0700)
Subject: proc: put check_mem_permission after __get_free_page in mem_write
X-Git-Tag: v3.0-rc1~76
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=30cd8903913dac7b0918807cac46be3ecde5a5a7;p=pandora-kernel.git

proc: put check_mem_permission after __get_free_page in mem_write

It whould be better if put check_mem_permission after __get_free_page in
mem_write, to be same as function mem_read.

Hugh Dickins explained the reason.

    check_mem_permission gets a reference to the mm.  If we __get_free_page
    after check_mem_permission, imagine what happens if the system is out
    of memory, and the mm we're looking at is selected for killing by the
    OOM killer: while we wait in __get_free_page for more memory, no memory
    is freed from the selected mm because it cannot reach exit_mmap while
    we hold that reference.

Reported-by: Jovi Zhang <bookjovi@gmail.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Stephen Wilson <wilsons@start.ca>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---

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