Re: [Xen-devel] [PATCH] gnttab: fix page_alloc + grant_table deadlock

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 05.11.13 at 21:46, Matt Wilson <msw@xxxxxxxxx> wrote:
> On Thu, Oct 31, 2013 at 09:29:16PM +0100, Radim KrÄmÃÅ wrote:
>> The patch takes grant_table->lock first in gnttab_transfer() and keeps
>> it longer, which also saves one unlock()+lock().
>> 
>> Based on analysis from Ulrich Obergfell <uobergfe@xxxxxxxxxx>.
> 
> This is XSA-73. This patch is much smaller than the patches provided
> in the advisory. Andrew, can you comment on why your fix should be
> applied instead of this one?

I think the reason is quite obvious: Extending a locked region is
always a bad idea if there's an alternative not doing so. The more
so for locks we know can be heavily contended.

Jan

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