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* [PATCH] xen/p2m: Fix one by off error in checking the P2M tree directory.
@ 2012-09-04 20:17 Konrad Rzeszutek Wilk
  2012-09-04 20:44 ` Konrad Rzeszutek Wilk
  0 siblings, 1 reply; 2+ messages in thread
From: Konrad Rzeszutek Wilk @ 2012-09-04 20:17 UTC (permalink / raw)
  To: linux-kernel; +Cc: xen-devel, Konrad Rzeszutek Wilk

We would the full P2M top directory from 0->MAX_DOMAIN_PAGES (inclusive).

Which meant that if the kernel was compiled with MAX_DOMAIN_PAGES=512
we would try to use the 512th entry. Fortunately for us the p2m_top_index
has a check for this:

 BUG_ON(pfn >= MAX_P2M_PFN);

which we hit and saw this:

(XEN) domain_crash_sync called from entry.S
(XEN) Domain 0 (vcpu#0) crashed on cpu#0:
(XEN) ----[ Xen-4.1.2-OVM  x86_64  debug=n  Tainted:    C ]----
(XEN) CPU:    0
(XEN) RIP:    e033:[<ffffffff819cadeb>]
(XEN) RFLAGS: 0000000000000212   EM: 1   CONTEXT: pv guest
(XEN) rax: ffffffff81db5000   rbx: ffffffff81db4000   rcx: 0000000000000000
(XEN) rdx: 0000000000480211   rsi: 0000000000000000   rdi: ffffffff81db4000
(XEN) rbp: ffffffff81793db8   rsp: ffffffff81793d38   r8:  0000000008000000
(XEN) r9:  4000000000000000   r10: 0000000000000000   r11: ffffffff81db7000
(XEN) r12: 0000000000000ff8   r13: ffffffff81df1ff8   r14: ffffffff81db6000
(XEN) r15: 0000000000000ff8   cr0: 000000008005003b   cr4: 00000000000026f0
(XEN) cr3: 0000000661795000   cr2: 0000000000000000

Fixes-Oracle-Bug: 14570662
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 arch/x86/xen/p2m.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 0bfaf5b..af11f00 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -695,7 +695,7 @@ bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_
 	if (p2m_index(set_pfn))
 		return false;
 
-	for (pfn = 0; pfn <= MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
+	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
 		topidx = p2m_top_index(pfn);
 
 		if (!p2m_top[topidx])
-- 
1.7.7.6


^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH] xen/p2m: Fix one by off error in checking the P2M tree directory.
  2012-09-04 20:17 [PATCH] xen/p2m: Fix one by off error in checking the P2M tree directory Konrad Rzeszutek Wilk
@ 2012-09-04 20:44 ` Konrad Rzeszutek Wilk
  0 siblings, 0 replies; 2+ messages in thread
From: Konrad Rzeszutek Wilk @ 2012-09-04 20:44 UTC (permalink / raw)
  To: linux-kernel; +Cc: xen-devel

On Tue, Sep 04, 2012 at 04:17:14PM -0400, Konrad Rzeszutek Wilk wrote:
> We would the full P2M top directory from 0->MAX_DOMAIN_PAGES (inclusive).

.. We would traverse the full P2M top directory (from 0->MAX_DOMAIN_PAGES
inclusive) when trying to figure out whether we can re-use some of the
P2M middle leafs.

> 
> Which meant that if the kernel was compiled with MAX_DOMAIN_PAGES=512
> we would try to use the 512th entry. Fortunately for us the p2m_top_index
> has a check for this:
> 
>  BUG_ON(pfn >= MAX_P2M_PFN);
> 
> which we hit and saw this:
> 
> (XEN) domain_crash_sync called from entry.S
> (XEN) Domain 0 (vcpu#0) crashed on cpu#0:
> (XEN) ----[ Xen-4.1.2-OVM  x86_64  debug=n  Tainted:    C ]----
> (XEN) CPU:    0
> (XEN) RIP:    e033:[<ffffffff819cadeb>]
> (XEN) RFLAGS: 0000000000000212   EM: 1   CONTEXT: pv guest
> (XEN) rax: ffffffff81db5000   rbx: ffffffff81db4000   rcx: 0000000000000000
> (XEN) rdx: 0000000000480211   rsi: 0000000000000000   rdi: ffffffff81db4000
> (XEN) rbp: ffffffff81793db8   rsp: ffffffff81793d38   r8:  0000000008000000
> (XEN) r9:  4000000000000000   r10: 0000000000000000   r11: ffffffff81db7000
> (XEN) r12: 0000000000000ff8   r13: ffffffff81df1ff8   r14: ffffffff81db6000
> (XEN) r15: 0000000000000ff8   cr0: 000000008005003b   cr4: 00000000000026f0
> (XEN) cr3: 0000000661795000   cr2: 0000000000000000
> 
> Fixes-Oracle-Bug: 14570662
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> ---
>  arch/x86/xen/p2m.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
> index 0bfaf5b..af11f00 100644
> --- a/arch/x86/xen/p2m.c
> +++ b/arch/x86/xen/p2m.c
> @@ -695,7 +695,7 @@ bool __init early_can_reuse_p2m_middle(unsigned long set_pfn, unsigned long set_
>  	if (p2m_index(set_pfn))
>  		return false;
>  
> -	for (pfn = 0; pfn <= MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
> +	for (pfn = 0; pfn < MAX_DOMAIN_PAGES; pfn += P2M_PER_PAGE) {
>  		topidx = p2m_top_index(pfn);
>  
>  		if (!p2m_top[topidx])
> -- 
> 1.7.7.6

^ permalink raw reply	[flat|nested] 2+ messages in thread

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