| Subject | Re: [patch V4 part 1 02/36] x86/hw_breakpoint: Prevent data breakpoints on cpu_entry_area | From | Alexandre Chartre <> | Date | Wed, 6 May 2020 14:11:45 +0200 |
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On 5/5/20 3:16 PM, Thomas Gleixner wrote: > From: Andy Lutomirski <luto@kernel.org> > > A data breakpoint near the top of an IST stack will cause unresoverable
typo: unresoverable -> unrecoverable
> recursion. A data breakpoint on the GDT, IDT, or TSS is terrifying. > Prevent either of these from happening. > > Co-developed-by: Peter Zijlstra <peterz@infradead.org> > Signed-off-by: Andy Lutomirski <luto@kernel.org> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> > --- > arch/x86/kernel/hw_breakpoint.c | 25 +++++++++++++++++++++++++ > 1 file changed, 25 insertions(+)
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
alex.
> --- a/arch/x86/kernel/hw_breakpoint.c > +++ b/arch/x86/kernel/hw_breakpoint.c > @@ -227,10 +227,35 @@ int arch_check_bp_in_kernelspace(struct > return (va >= TASK_SIZE_MAX) || ((va + len - 1) >= TASK_SIZE_MAX); > } > > +/* > + * Checks whether the range from addr to end, inclusive, overlaps the CPU > + * entry area range. > + */ > +static inline bool within_cpu_entry_area(unsigned long addr, unsigned long end) > +{ > + return end >= CPU_ENTRY_AREA_PER_CPU && > + addr < (CPU_ENTRY_AREA_PER_CPU + CPU_ENTRY_AREA_TOTAL_SIZE); > +} > + > static int arch_build_bp_info(struct perf_event *bp, > const struct perf_event_attr *attr, > struct arch_hw_breakpoint *hw) > { > + unsigned long bp_end; > + > + bp_end = attr->bp_addr + attr->bp_len - 1; > + if (bp_end < attr->bp_addr) > + return -EINVAL; > + > + /* > + * Prevent any breakpoint of any type that overlaps the > + * cpu_entry_area. This protects the IST stacks and also > + * reduces the chance that we ever find out what happens if > + * there's a data breakpoint on the GDT, IDT, or TSS. > + */ > + if (within_cpu_entry_area(attr->bp_addr, bp_end)) > + return -EINVAL; > + > hw->address = attr->bp_addr; > hw->mask = 0; > >
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