x86/entry/64: Remove the SYSENTER stack canary

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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bpetkov@suse.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Laight <David.Laight@aculab.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Eduardo Valentin <eduval@amazon.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: aliguori@amazon.com
Cc: daniel.gruss@iaik.tugraz.at
Cc: hughd@google.com
Cc: keescook@google.com
Link: https://lkml.kernel.org/r/20171204150606.572577316@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b0cf0612a454d62f4772da95a77982b3105429a2..d34ac13c586652a195774dd7957ded83574c6f5b 100644 (file)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -341,7 +341,6 @@ 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 60267850125e68bb6a65a9d0095502d34a305ebf..ae1ce2e3f132603f0d638c6880dd63f62769a1a1 100644 (file)
--- 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 86e83762e3b3789f4582d4510214181750b5b8a5..6a04287f222b29a750860870c02199ebf5cb216b 100644 (file)
--- 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 3e29aad5c7cc67f874a9f9fd905481380e520946..5ade4f89a6d1695eb537e9d25120fc75f924c37c 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -814,13 +814,6 @@ 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);