[uml-devel] fix SEGV in handle_page_fault() when current->mm is NULL

[uml-devel] fix SEGV in handle_page_fault() when current->mm is NULL

[Nicolas S. Dade]

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In a non-uml kernel a get_user() when current->mm is NULL (kernel thread, or
userspace process being torn down) returns error. In uml it SEGVs. The bug is
that handle_page_fault() does not check for NULL before using mm. The
trivial attached patch fixes this.

-Nicolas Dade

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--- linux-2.6.21.2/arch/um/kernel/trap.c.orig	2007-05-24 02:22:42.000000000 -0700
+++ linux-2.6.21.2/arch/um/kernel/trap.c	2007-05-24 02:23:45.000000000 -0700
@@ -51,6 +51,9 @@
 	 * fail. */
 	if (in_atomic())
 		goto out_nosemaphore;
+	/* If we have no user-space just fail */
+	if (!mm)
+		goto out_nosemaphore;
 
 	down_read(&mm->mmap_sem);
 	vma = find_vma(mm, address);

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Re: [uml-devel] fix SEGV in handle_page_fault() when current->mm is NULL

[Blaisorblade]

On giovedì 24 maggio 2007, Nicolas S. Dade wrote:
> In a non-uml kernel a get_user() when current->mm is NULL (kernel thread,
> or userspace process being torn down) returns error. In uml it SEGVs. The
> bug is that handle_page_fault() does not check for NULL before using mm.
> The trivial attached patch fixes this.
>
> -Nicolas Dade

Acked-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>

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Inform me of my mistakes, so I can add them to my list!
Paolo Giarrusso, aka Blaisorblade
http://www.user-mode-linux.org/~blaisorblade

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Re: [uml-devel] fix SEGV in handle_page_fault() when current->mm is NULL

[Jeff Dike]

On Thu, May 24, 2007 at 02:29:04AM -0700, Nicolas S. Dade wrote:
> In a non-uml kernel a get_user() when current->mm is NULL (kernel thread, or
> userspace process being torn down) returns error. In uml it SEGVs. The bug is
> that handle_page_fault() does not check for NULL before using mm. The
> trivial attached patch fixes this.

Can I have a Signed-off-by on this?

				Jeff

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