linux-kernel - [PATCH 4.19 271/306] x86/doublefault/32: Fix stack canaries in the double fault handler

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Message-Id: <20191127203134.623566738@linuxfoundation.org>
Date:   Wed, 27 Nov 2019 21:32:01 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, stable@...nel.org
Subject: [PATCH 4.19 271/306] x86/doublefault/32: Fix stack canaries in the double fault handler

From: Andy Lutomirski <luto@...nel.org>

commit 3580d0b29cab08483f84a16ce6a1151a1013695f upstream.

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

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: stable@...nel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kernel/doublefault.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/x86/kernel/doublefault.c
+++ b/arch/x86/kernel/doublefault.c
@@ -65,6 +65,9 @@ struct x86_hw_tss doublefault_tss __cach
 	.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),
 };