It's the 'addr' input to mmap(), and currently consuming stack rubble.
Coverity-ID: 1500115
Fixes: c7a7f14b92 ("tests/resource: Extend to check that the grant frames are mapped correctly")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>