linux-kernel - [PATCH 3.12 20/39] m68k/mm: Check for mm != NULL in do_page

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Date:	Mon, 25 Jan 2016 12:50:01 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	stable@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Oliver Neukum <ONeukum@...e.com>, Jiri Slaby <jslaby@...e.cz>
Subject: [PATCH 3.12 20/39] m68k/mm: Check for mm != NULL in do_page_fault() debug code

From: Geert Uytterhoeven <geert@...ux-m68k.org>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 4e25c0e92f8eaf69bc51d1d523bcb7268e7dd162 upstream.

When DEBUG is enabled, do_page_fault() may dereference a NULL pointer,
causing recursive bus errors.

Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: Oliver Neukum <ONeukum@...e.com>
Signed-off-by: Jiri Slaby <jslaby@...e.cz>
---
 arch/m68k/mm/fault.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/m68k/mm/fault.c b/arch/m68k/mm/fault.c
index f0eef0491f77..97136b5e47e0 100644
--- a/arch/m68k/mm/fault.c
+++ b/arch/m68k/mm/fault.c
@@ -77,8 +77,7 @@ int do_page_fault(struct pt_regs *regs, unsigned long address,
 
 #ifdef DEBUG
 	printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
-		regs->sr, regs->pc, address, error_code,
-		current->mm->pgd);
+		regs->sr, regs->pc, address, error_code, mm ? mm->pgd : NULL);
 #endif
 
 	/*
-- 
2.7.0