Description: netback fails to honor grant mapping errors
References:
 https://xenbits.xen.org/xsa/advisory-367.html
 https://lore.kernel.org/lkml/20210304110053.8787-1-jgross@suse.com/
Notes:
Bugs:
upstream: released (5.12-rc2) [8310b77b48c5558c140e7a57a702e7819e62f04e, 2991397d23ec597405b116d96de3813420bdcbc3]
5.10-upstream-stable: released (5.10.21) [545c837d6789afcb23da5494a22e459952fb823f, fa00c0c826ddea48e0dc9c7944506dd67a7be6d2]
4.19-upstream-stable: released (4.19.179) [1a999d25ef536a14f6a7c25778836857adfba3f8, b62d8b5c814be957ce164453ddf4852167908841]
4.9-upstream-stable: released (4.9.260)  [d1ae0cfd1fab27d170caf905e519198cb144d523, 2154a1c60be3ccf59b62af636acd2aa44a531432]
sid: released (5.10.24-1)
4.19-buster-security: released (4.19.181-1)
4.9-stretch-security: released (4.9.258-1) [bugfix/all/xen-gnttab-handle-p2m-update-errors-on-a-per-slot-ba.patch, bugfix/all/xen-netback-respect-gnttab_map_refs-s-return-value.patch]