Re: [BUGFIX] NULL pointer dereference in __vm_enough_memory()

From: Fengguang Wu
Date: Sun Aug 12 2007 - 01:29:48 EST


On Sat, Aug 11, 2007 at 06:17:14PM +0400, Cyrill Gorcunov wrote:
> [Fengguang Wu - Sat, Aug 11, 2007 at 09:21:31PM +0800]
> | Andrew,
> |
> | I'm not sure if this patch is the right fix for the bug. But it do
> | stops the oops message. The bug also happens in 2.6.23-rc1-mm2/2.6.23-rc2-mm2.
> | I'm running debian/sid. The .config is attached.
> |
> |
>
> [...snip...]
>
> Even if you're right you have to make the same patch for
> mm/nommu.c but I've an anticipation the problem is growing
> up from another point (and I'm really hoping that I'm wrong ;)

Thank you, the patch is updated to:
===

Fix possible NULL pointer deference on __vm_enough_memory().

Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
---
mm/mmap.c | 3 ++-
mm/nommu.c | 3 ++-
2 files changed, 4 insertions(+), 2 deletions(-)

--- linux-2.6.23-rc2-mm2.orig/mm/mmap.c
+++ linux-2.6.23-rc2-mm2/mm/mmap.c
@@ -166,7 +166,8 @@ int __vm_enough_memory(long pages, int c

/* Don't let a single process grow too big:
leave 3% of the size of this process for other processes */
- allowed -= current->mm->total_vm / 32;
+ if (current->mm)
+ allowed -= current->mm->total_vm / 32;

/*
* cast `allowed' as a signed long because vm_committed_space
--- linux-2.6.23-rc2-mm2.orig/mm/nommu.c
+++ linux-2.6.23-rc2-mm2/mm/nommu.c
@@ -1342,7 +1342,8 @@ int __vm_enough_memory(long pages, int c

/* Don't let a single process grow too big:
leave 3% of the size of this process for other processes */
- allowed -= current->mm->total_vm / 32;
+ if (current->mm)
+ allowed -= current->mm->total_vm / 32;

/*
* cast `allowed' as a signed long because vm_committed_space

-
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