The following commit has been merged into the x86/entry branch of tip: Commit-ID: 3ea11ac991d594728e5df42f7eb1145072b9c2bc Gitweb: https://git.kernel.org/tip/3ea11ac991d594728e5df42f7eb1145072b9c2bc Author: Andy Lutomirski <l...@kernel.org> AuthorDate: Mon, 24 Feb 2020 13:24:58 +01:00 Committer: Thomas Gleixner <t...@linutronix.de> CommitterDate: Fri, 15 May 2020 20:03:03 +02:00
x86/hw_breakpoint: Prevent data breakpoints on cpu_entry_area A data breakpoint near the top of an IST stack will cause 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> Reviewed-by: Borislav Petkov <b...@suse.de> Reviewed-by: Lai Jiangshan <jiangshan...@gmail.com> Reviewed-by: Alexandre Chartre <alexandre.char...@oracle.com> Link: https://lkml.kernel.org/r/20200505134058.272448...@linutronix.de --- arch/x86/kernel/hw_breakpoint.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index 4d8d53e..d42fc0e 100644 --- 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 arch_hw_breakpoint *hw) 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_BASE && + addr < (CPU_ENTRY_AREA_BASE + 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;
