On 5/5/20 3:16 PM, Thomas Gleixner wrote:
From: Andy Lutomirski <l...@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 <pet...@infradead.org> Signed-off-by: Andy Lutomirski <l...@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- arch/x86/kernel/hw_breakpoint.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
Reviewed-by: Alexandre Chartre <alexandre.char...@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;
