From ff8b16d7e15a8ba2a6086645614a483e048e3fbf Mon Sep 17 00:00:00 2001
From: Wu Fengguang <fengguang.wu@intel.com>
Date: Thu, 4 Nov 2010 01:56:49 +0800
Subject: vmstat: fix offset calculation on void*

Fix regression introduced by commit 79da826aee6 ("writeback: report
dirty thresholds in /proc/vmstat").

The incorrect pointer arithmetic can result in problems like this:

  BUG: unable to handle kernel paging request at 07c06d16
  IP: [<c050c336>] strnlen+0x6/0x20
  Call Trace:
   [<c050a249>] ? string+0x39/0xe0
   [<c042be6b>] ? __wake_up_common+0x4b/0x80
   [<c050afcc>] ? vsnprintf+0x1ec/0x380
   [<c04b380e>] ? seq_printf+0x2e/0x60
   [<c04829a6>] ? vmstat_show+0x26/0x30
   [<c04b3bb6>] ? seq_read+0xa6/0x380
   [<c04b3b10>] ? seq_read+0x0/0x380
   [<c04d5d2f>] ? proc_reg_read+0x5f/0x90
   [<c049c4a1>] ? vfs_read+0xa1/0x140
   [<c04d5cd0>] ? proc_reg_read+0x0/0x90
   [<c049c981>] ? sys_read+0x41/0x70
   [<c0402bd0>] ? sysenter_do_call+0x12/0x26

Reported-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Michael Rubin <mrubin@google.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 mm/vmstat.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

(limited to 'mm')

diff --git a/mm/vmstat.c b/mm/vmstat.c
index cd2e42be..42eac4d 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -949,7 +949,7 @@ static void *vmstat_start(struct seq_file *m, loff_t *pos)
 	v[PGPGIN] /= 2;		/* sectors -> kbytes */
 	v[PGPGOUT] /= 2;
 #endif
-	return m->private + *pos;
+	return (unsigned long *)m->private + *pos;
 }
 
 static void *vmstat_next(struct seq_file *m, void *arg, loff_t *pos)
-- 
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