[PATCH] x86/vmx: Avoid hitting BUG_ON() after EPTP-related domain_crash()

[PATCH] x86/vmx: Avoid hitting BUG_ON() after EPTP-related domain_crash()

[Andrew Cooper]

If the EPTP pointer can't be located in the altp2m list, the domain
is (legitimately) crashed.

Under those circumstances, execution will continue and guarentee to hit the
BUG_ON(idx >= MAX_ALTP2M) (unfortunately, just out of context).

Return from vmx_vmexit_handler() after the domain_crash(), which also has the
side effect of reentering the scheduler more promptly.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Jun Nakajima <jun.nakajima@intel.com>
CC: Kevin Tian <kevin.tian@intel.com>
CC: Razvan Cojocaru <rcojocaru@bitdefender.com>
CC: Tamas K Lengyel <tamas@tklengyel.com>
---
 xen/arch/x86/hvm/vmx/vmx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index bcf95f9..257efbe 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -3666,6 +3666,8 @@ void vmx_vmexit_handler(struct cpu_user_regs *regs)
             {
                 gdprintk(XENLOG_ERR, "EPTP not found in alternate p2m list\n");
                 domain_crash(v->domain);
+
+                return;
             }
         }
 
-- 
2.1.4


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Re: [PATCH] x86/vmx: Avoid hitting BUG_ON() after EPTP-related domain_crash()

[Razvan Cojocaru]

On 08/01/2018 03:07 PM, Andrew Cooper wrote:
> If the EPTP pointer can't be located in the altp2m list, the domain
> is (legitimately) crashed.
> 
> Under those circumstances, execution will continue and guarentee to hit the
> BUG_ON(idx >= MAX_ALTP2M) (unfortunately, just out of context).
> 
> Return from vmx_vmexit_handler() after the domain_crash(), which also has the
> side effect of reentering the scheduler more promptly.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Reviewed-by: Razvan Cojocaru <rcojocaru@bitdefender.com>


Thanks,
Razvan

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Re: [PATCH] x86/vmx: Avoid hitting BUG_ON() after EPTP-related domain_crash()

[Tian, Kevin]

> From: Andrew Cooper [mailto:andrew.cooper3@citrix.com]
> Sent: Wednesday, August 1, 2018 8:08 PM
> 
> If the EPTP pointer can't be located in the altp2m list, the domain
> is (legitimately) crashed.
> 
> Under those circumstances, execution will continue and guarentee to hit
> the
> BUG_ON(idx >= MAX_ALTP2M) (unfortunately, just out of context).
> 
> Return from vmx_vmexit_handler() after the domain_crash(), which also
> has the
> side effect of reentering the scheduler more promptly.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Kevin Tian <kevin.tian@intel.com>

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