From c4a323871bc221fd11b51c62a3bccf2ea2b9fddd Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 20 Nov 2017 12:38:44 +0100 Subject: [PATCH] s390: always save and restore all registers on context switch commit fbbd7f1a51965b50dd12924841da0d478f3da71b upstream. The switch_to() macro has an optimization to avoid saving and restoring register contents that aren't needed for kernel threads. There is however the possibility that a kernel thread execve's a user space program. In such a case the execve'd process can partially see the contents of the previous process, which shouldn't be allowed. To avoid this, simply always save and restore register contents on context switch. Fixes: fdb6d070effba ("switch_to: dont restore/save access & fpu regs for kernel threads") Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky [bwh: Backported to 3.2: - The save/restore functions are different here - FP restore is non-lazy, so drop the comment about it being lazy - Adjust filename] Signed-off-by: Ben Hutchings --- Reading git-format-patch failed