From: Andy Lutomirski <l...@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 <l...@kernel.org> Signed-off-by: Ingo Molnar <mi...@kernel.org> Signed-off-by: Thomas Gleixner <t...@linutronix.de> Reviewed-by: Thomas Gleixner <t...@linutronix.de> Reviewed-by: Borislav Petkov <b...@suse.de> Cc: Rik van Riel <r...@redhat.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Brian Gerst <brge...@gmail.com> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Link: https://lkml.kernel.org/r/be3179c0a38c392fa44ebeb7dd89391ff5c010c3.1511497875.git.l...@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(-) --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -342,7 +342,6 @@ 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]; /* --- a/arch/x86/kernel/dumpstack.c +++ b/arch/x86/kernel/dumpstack.c @@ -48,8 +48,7 @@ bool in_sysenter_stack(unsigned long *st 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) --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -81,7 +81,6 @@ */ .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 }, #endif - .SYSENTER_stack_canary = STACK_END_MAGIC, }; EXPORT_PER_CPU_SYMBOL(cpu_tss); --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -819,13 +819,6 @@ dotraplinkage void do_debug(struct pt_re 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);