On Sat, Mar 05, 2016 at 09:52:23PM -0800, Andy Lutomirski wrote:
<--- ?
So all patches before are nice and verbose in explaining what they do.
Where did the commit message of this one disappear?
:-)
Or is it that obvious that we should have a stack canary? How about some
text *why* we need it?
> Signed-off-by: Andy Lutomirski <l...@kernel.org>
> ---
> arch/x86/include/asm/processor.h | 3 ++-
> arch/x86/kernel/process.c | 3 +++
> arch/x86/kernel/traps.c | 8 ++++++++
> 3 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/processor.h
> b/arch/x86/include/asm/processor.h
> index 7cd01b71b5bd..50a6dc871cc0 100644
> --- a/arch/x86/include/asm/processor.h
> +++ b/arch/x86/include/asm/processor.h
> @@ -299,8 +299,9 @@ struct tss_struct {
>
> #ifdef CONFIG_X86_32
> /*
> - * Space for the temporary SYSENTER stack:
> + * Space for the temporary SYSENTER stack.
> */
> + unsigned long SYSENTER_stack_canary;
> unsigned long SYSENTER_stack[64];
> #endif
>
> diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> index 9f7c21c22477..ee9a9792caeb 100644
> --- a/arch/x86/kernel/process.c
> +++ b/arch/x86/kernel/process.c
> @@ -57,6 +57,9 @@ __visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct,
> cpu_tss) = {
> */
> .io_bitmap = { [0 ... IO_BITMAP_LONGS] = ~0 },
> #endif
> +#ifdef CONFIG_X86_32
> + .SYSENTER_stack_canary = STACK_END_MAGIC,
> +#endif
> };
> EXPORT_PER_CPU_SYMBOL(cpu_tss);
>
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index 80928ea78373..590110119e6a 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -713,6 +713,14 @@ dotraplinkage void do_debug(struct pt_regs *regs, long
> error_code)
> debug_stack_usage_dec();
>
> exit:
> +#if defined(CONFIG_X86_32)
> + /*
> + * 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");
> +#endif
> ist_exit(regs);
> }
> NOKPROBE_SYMBOL(do_debug);
> --
> 2.5.0
>
>
--
Regards/Gruss,
Boris.
ECO tip #101: Trim your mails when you reply.
