[tip: x86/urgent] x86/doublefault/32: Fix stack canaries in the double fault handler

[tip-bot2 for Andy Lutomirski]

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     3580d0b29cab08483f84a16ce6a1151a1013695f
Gitweb:        https://git.kernel.org/tip/3580d0b29cab08483f84a16ce6a1151a1013695f
Author:        Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate:    Thu, 21 Nov 2019 11:50:12 +01:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Thu, 21 Nov 2019 19:37:42 +01:00

x86/doublefault/32: Fix stack canaries in the double fault handler

The double fault TSS was missing GS setup, which is needed for stack
canaries to work.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxx
---
 arch/x86/kernel/doublefault.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kernel/doublefault.c b/arch/x86/kernel/doublefault.c
index 0b8cedb..d5c9b13 100644
--- a/arch/x86/kernel/doublefault.c
+++ b/arch/x86/kernel/doublefault.c
@@ -65,6 +65,9 @@ struct x86_hw_tss doublefault_tss __cacheline_aligned = {
 	.ss		= __KERNEL_DS,
 	.ds		= __USER_DS,
 	.fs		= __KERNEL_PERCPU,
+#ifndef CONFIG_X86_32_LAZY_GS
+	.gs		= __KERNEL_STACK_CANARY,
+#endif
 
 	.__cr3		= __pa_nodebug(swapper_pg_dir),
 };