[PATCH AUTOSEL 4.14 65/67] x86/pti: Check the return value of pti_user_pagetable_walk_p4d()

From: Jiang Biao [ Upstream commit b2b7d986a89b6c94b1331a909de1217214fb08c1 ] pti_user_pagetable_walk_p4d() can return NULL, so the return value should be checked to prevent a NULL pointer dereference. Add the check and a warning when the P4D allocation fails. Signed-off-by: Jiang Biao

[PATCH AUTOSEL 4.14 65/67] x86/pti: Check the return value of pti_user_pagetable_walk_p4d()

From: Jiang Biao [ Upstream commit b2b7d986a89b6c94b1331a909de1217214fb08c1 ] pti_user_pagetable_walk_p4d() can return NULL, so the return value should be checked to prevent a NULL pointer dereference. Add the check and a warning when the P4D allocation fails. Signed-off-by: Jiang Biao