linux-kernel - [PATCH] Re: [SPARC32] NULL pointer derefference

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Message-ID: <Pine.LNX.4.61.0707310831080.4116@mtfhpc.demon.co.uk>
Date:	Tue, 31 Jul 2007 08:55:20 +0100 (BST)
From:	Mark Fortescue <mark@...hpc.demon.co.uk>
To:	David Miller <davem@...emloft.net>
cc:	aaw@...gle.com, akpm@...ux-foundation.org,
	linux-arch@...r.kernel.org, sparclinux@...r.kernel.org,
	wli@...omorphy.com, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] Re: [SPARC32] NULL pointer derefference

Hi David,

I have formulated a patch that prevents the update_mmu_cache from doing 
enything if there is no context available. This apears to have no 
immediate, undesirable side effects.

This worked better than the alternative of setting up a context to work with.

Can you for see any issues in doing this?

If not, can you check+apply the attached (un-mangled) patch.

diff -ruNpd linux-2.6/arch/sparc/mm/sun4c.c linux-test/arch/sparc/mm/sun4c.c
--- linux-2.6/arch/sparc/mm/sun4c.c	2007-07-30 03:19:15.000000000 +0100
+++ linux-test/arch/sparc/mm/sun4c.c	2007-07-31 08:28:13.000000000 +0100
@@ -1999,6 +2029,9 @@ void sun4c_update_mmu_cache(struct vm_ar
  	unsigned long flags;
  	int pseg;

+	if (vma->vm_mm->context == NO_CONTEXT)
+		return;
+
  	local_irq_save(flags);
  	address &= PAGE_MASK;
  	if ((pseg = sun4c_get_segmap(address)) == invalid_segment) {

Regards
 	Mark Fortescue.
View attachment "mmu-cache-fix.patch" of type "TEXT/PLAIN" (1184 bytes)