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From: Andy Lutomirski <luto@kernel.org>
To: X86 ML <x86@kernel.org>
Cc: Borislav Petkov <bpetkov@suse.de>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Brian Gerst <brgerst@gmail.com>,
	Dave Hansen <dave.hansen@intel.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Josh Poimboeuf <jpoimboe@redhat.com>,
	Andy Lutomirski <luto@kernel.org>
Subject: [PATCH v3 18/19] x86/entry/64: Remove the SYSENTER stack canary
Date: Thu, 23 Nov 2017 20:33:04 -0800
Message-ID: <be3179c0a38c392fa44ebeb7dd89391ff5c010c3.1511497875.git.luto@kernel.org> (raw)
In-Reply-To: <cover.1511497874.git.luto@kernel.org>
In-Reply-To: <cover.1511497874.git.luto@kernel.org>

Now that the SYSENTER stack has a guard page, there's no need for a
canary to detect overflow after the fact.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
 arch/x86/include/asm/processor.h | 1 -
 arch/x86/kernel/dumpstack.c      | 3 +--
 arch/x86/kernel/process.c        | 1 -
 arch/x86/kernel/traps.c          | 7 -------
 4 files changed, 1 insertion(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 3a09e5571a92..7743aedb82ea 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -337,7 +337,6 @@ struct tss_struct {
 	 * Space for the temporary SYSENTER stack, used for SYSENTER
 	 * and the entry trampoline as well.
 	 */
-	unsigned long		SYSENTER_stack_canary;
 	unsigned long		SYSENTER_stack[64];
 
 	/*
diff --git a/arch/x86/kernel/dumpstack.c b/arch/x86/kernel/dumpstack.c
index bb61919c9335..9ce5fcf7d14d 100644
--- a/arch/x86/kernel/dumpstack.c
+++ b/arch/x86/kernel/dumpstack.c
@@ -48,8 +48,7 @@ bool in_sysenter_stack(unsigned long *stack, struct stack_info *info)
 	int cpu = smp_processor_id();
 	struct tss_struct *tss = &get_cpu_entry_area(cpu)->tss;
 
-	/* Treat the canary as part of the stack for unwinding purposes. */
-	void *begin = &tss->SYSENTER_stack_canary;
+	void *begin = &tss->SYSENTER_stack;
 	void *end = (void *)&tss->SYSENTER_stack + sizeof(tss->SYSENTER_stack);
 
 	if ((void *)stack < begin || (void *)stack >= end)
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 86e83762e3b3..6a04287f222b 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -81,7 +81,6 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, cpu_tss) = {
 	  */
 	.io_bitmap		= { [0 ... IO_BITMAP_LONGS] = ~0 },
 #endif
-	.SYSENTER_stack_canary	= STACK_END_MAGIC,
 };
 EXPORT_PER_CPU_SYMBOL(cpu_tss);
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index cbc4272bb9dd..19475dbff068 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -801,13 +801,6 @@ dotraplinkage void do_debug(struct pt_regs *regs, long error_code)
 	debug_stack_usage_dec();
 
 exit:
-	/*
-	 * This is the most likely code path that involves non-trivial use
-	 * of the SYSENTER stack.  Check that we haven't overrun it.
-	 */
-	WARN(this_cpu_read(cpu_tss.SYSENTER_stack_canary) != STACK_END_MAGIC,
-	     "Overran or corrupted SYSENTER stack\n");
-
 	ist_exit(regs);
 }
 NOKPROBE_SYMBOL(do_debug);
-- 
2.13.6

  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-11-24  4:32 [PATCH v3 00/19] Entry stack switching Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 01/19] x86/asm/64: Allocate and enable the SYSENTER stack Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 02/19] x86/dumpstack: Add get_stack_info() support for " Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 03/19] x86/gdt: Put per-cpu GDT remaps in ascending order Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 04/19] x86/fixmap: Generalize the GDT fixmap mechanism Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 05/19] x86/kasan/64: Teach KASAN about the cpu_entry_area Andy Lutomirski
2017-11-24 13:16   ` Andrey Ryabinin
2017-11-24 16:27     ` Andy Lutomirski
2017-11-24 17:21       ` [PATCH v4] x86/mm/kasan: " Andrey Ryabinin
2017-11-24 19:26         ` Andy Lutomirski
2017-11-24 17:26       ` [PATCH v3 05/19] x86/kasan/64: " Andrey Ryabinin
2017-11-24  4:32 ` [PATCH v3 06/19] x86/asm: Fix assumptions that the HW TSS is at the beginning of cpu_tss Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 07/19] x86/dumpstack: Handle stack overflow on all stacks Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 08/19] x86/asm: Move SYSENTER_stack to the beginning of struct tss_struct Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 09/19] x86/asm: Remap the TSS into the cpu entry area Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 10/19] x86/asm/64: Separate cpu_current_top_of_stack from TSS.sp0 Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 11/19] x86/espfix/64: Stop assuming that pt_regs is on the entry stack Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 12/19] x86/asm/64: Use a percpu trampoline stack for IDT entries Andy Lutomirski
2017-11-24  4:32 ` [PATCH v3 13/19] x86/asm/64: Return to userspace from the trampoline stack Andy Lutomirski
2017-11-24  4:33 ` [PATCH v3 14/19] x86/entry/64: Create a percpu SYSCALL entry trampoline Andy Lutomirski
2017-11-24 11:39   ` David Laight
2017-12-01  5:56     ` Andy Lutomirski
2017-11-24  4:33 ` [PATCH v3 15/19] x86/irq: Remove an old outdated comment about context tracking races Andy Lutomirski
2017-11-24  4:33 ` [PATCH v3 16/19] x86/irq/64: In the stack overflow warning, print the offending IP Andy Lutomirski
2017-11-24  4:33 ` [PATCH v3 17/19] x86/entry/64: Move the IST stacks into cpu_entry_area Andy Lutomirski
2017-11-24  4:33 ` Andy Lutomirski [this message]
2017-11-24  4:33 ` [PATCH v3 19/19] x86/entry: Clean up SYSENTER_stack code Andy Lutomirski

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