Messages in this thread | | | Date | Tue, 8 Mar 2016 07:40:24 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 10/10] x86/entry/32: Add and check a stack canary for the SYSENTER stack |
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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 <luto@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.
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