The following commit has been merged into the x86/entry branch of tip: Commit-ID: 9a06f99a03a0f961047bbae4ee80ce9265757bfe Gitweb: https://git.kernel.org/tip/9a06f99a03a0f961047bbae4ee80ce9265757bfe Author: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> AuthorDate: Fri, 29 May 2020 23:27:31 +02:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Sat, 30 May 2020 10:00:06 +02:00 x86/hw_breakpoint: Prevent data breakpoints on per_cpu cpu_tss_rw cpu_tss_rw is not directly referenced by hardware, but cpu_tss_rw is accessed in CPU entry code, especially when #DB shifts its stacks. If a data breakpoint would be set on cpu_tss_rw.x86_tss.ist[IST_INDEX_DB], it would cause recursive #DB ending up in a double fault. Add it to the list of protected items. Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/20200526014221.2119-4-laijs@xxxxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20200529213320.897976479@xxxxxxxxxxxxx --- arch/x86/kernel/hw_breakpoint.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index f859095..f311bbf 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -255,6 +255,15 @@ static inline bool within_cpu_entry(unsigned long addr, unsigned long end) if (within_area(addr, end, (unsigned long)get_cpu_gdt_rw(cpu), GDT_SIZE)) return true; + + /* + * cpu_tss_rw is not directly referenced by hardware, but + * cpu_tss_rw is also used in CPU entry code, + */ + if (within_area(addr, end, + (unsigned long)&per_cpu(cpu_tss_rw, cpu), + sizeof(struct tss_struct))) + return true; } return false;
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