Re: [Xen-devel] [PATCH] x86/nHVM: avoid NULL deref during INVLPG intercept handling

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 05/02/16 07:37, Jan Beulich wrote:
> When intercepting (or emulating) L1 guest INVLPG, the nested P2M
> pointer may be (is?) NULL, and hence there's no point in calling
> p2m_flush(). In fact doing so would cause a dereference of that NULL
> pointer at least in the ASSERT() right at the beginning of the
> function.
> 
> While so far nothing supports hap_invlpg() being reachable from the
> INVLPG intercept paths (only INVLPG insn emulation would lead there),
> and hence the code in question (added by dd6de3ab99 ["Implement
> Nested-on-Nested"]) appears to be dead, this seems to be the change
> which can be agreed on as an immediate fix. Ideally, however, the
> problematic code would go away altogether. See thread at
> lists.xenproject.org/archives/html/xen-devel/2016-01/msg03762.html.
>    
> Reported-by: ÃËËÃÂÂ <liuling-it@xxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: George Dunlap <george.dunlap@xxxxxxxxxx>



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