Re: [Xen-devel] [PATCH for-4.10] x86/hvm: Don't corrupt the HVM context stream when writing the MSR record

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Nov 16, 2017 at 10:45:16PM +0000, Andrew Cooper wrote:
> Ever since it was introduced in c/s bd1f0b45ff, hvm_save_cpu_msrs() has had a
> bug whereby it corrupts the HVM context stream if some, but fewer than the
> maximum number of MSRs are written.
> 
> _hvm_init_entry() creates an hvm_save_descriptor with length for
> msr_count_max, but in the case that we write fewer than max, h->cur only moves
> forward by the amount of space used, causing the subsequent
> hvm_save_descriptor to be written within the bounds of the previous one.
> 
> To resolve this, reduce the length reported by the descriptor to match the
> actual number of bytes used.
> 
> A typical failure on the destination side looks like:
> 
>     (XEN) HVM4 restore: CPU_MSR 0
>     (XEN) HVM4.0 restore: not enough data left to read 56 MSR bytes
>     (XEN) HVM4 restore: failed to load entry 20/0
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel