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Re: [PATCH v2] xen: detect uninitialized xenbus in xenbus_init
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>, jgross@xxxxxxxx
- From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
- Date: Fri, 19 Nov 2021 17:32:15 -0500
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- Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, jbeulich@xxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>, stable@xxxxxxxxxxxxxxx
- Delivery-date: Fri, 19 Nov 2021 22:32:41 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11/19/21 3:29 PM, Stefano Stabellini wrote:
From: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
If the xenstore page hasn't been allocated properly, reading the value
of the related hvm_param (HVM_PARAM_STORE_PFN) won't actually return
error. Instead, it will succeed and return zero. Instead of attempting
to xen_remap a bad guest physical address, detect this condition and
return early.
Note that although a guest physical address of zero for
HVM_PARAM_STORE_PFN is theoretically possible, it is not a good choice
and zero has never been validly used in that capacity.
Also recognize the invalid value of INVALID_PFN which is ULLONG_MAX.
For 32-bit Linux, any pfn above ULONG_MAX would get truncated. Pfns
above ULONG_MAX should never be passed by the Xen tools to HVM guests
anyway, so check for this condition and return early.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrvsky@xxxxxxxxxx>
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