linux-kernel - [PATCH v2 18/20] x86/boot/32: Fix cpu_current_top_of

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Message-Id: <e5e370a7e6e4fddd1c4e4cf619765d96bb874b21.1509609304.git.luto@kernel.org>
Date:   Thu,  2 Nov 2017 00:59:15 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     X86 ML <x86@...nel.org>
Cc:     Borislav Petkov <bpetkov@...e.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: [PATCH v2 18/20] x86/boot/32: Fix cpu_current_top_of_stack initialization at boot

cpu_current_top_of_stack's initialization forgot about
TOP_OF_KERNEL_STACK_PADDING.  This bug didn't matter because the
idle threads never enter user mode.

Reviewed-by: Borislav Petkov <bp@...e.de>
Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/kernel/smpboot.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ad59edd84de7..06c18fe1c09e 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -961,8 +961,7 @@ void common_cpu_up(unsigned int cpu, struct task_struct *idle)
 #ifdef CONFIG_X86_32
 	/* Stack for startup_32 can be just as for start_secondary onwards */
 	irq_ctx_init(cpu);
-	per_cpu(cpu_current_top_of_stack, cpu) =
-		(unsigned long)task_stack_page(idle) + THREAD_SIZE;
+	per_cpu(cpu_current_top_of_stack, cpu) = task_top_of_stack(idle);
 #else
 	initial_gs = per_cpu_offset(cpu);
 #endif
-- 
2.13.6