The following commit has been merged into the x86/entry branch of tip: Commit-ID: 87aa9b64e0ccb779db3970e2e9af1cc5930c2c3d Gitweb: https://git.kernel.org/tip/87aa9b64e0ccb779db3970e2e9af1cc5930c2c3d Author: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx> AuthorDate: Fri, 29 May 2020 23:27:32 +02:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Sat, 30 May 2020 10:00:06 +02:00 x86/hw_breakpoint: Prevent data breakpoints on user_pcid_flush_mask The per-CPU user_pcid_flush_mask is used in the low level entry code. A data breakpoint can cause #DB recursion. Protect the full cpu_tlbstate structure for simplicity. 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/20200526014221.2119-5-laijs@xxxxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20200529213320.955117574@xxxxxxxxxxxxx --- arch/x86/kernel/hw_breakpoint.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index f311bbf..fc1743a 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -33,6 +33,7 @@ #include <asm/debugreg.h> #include <asm/user.h> #include <asm/desc.h> +#include <asm/tlbflush.h> /* Per cpu debug control register value */ DEFINE_PER_CPU(unsigned long, cpu_dr7); @@ -264,6 +265,16 @@ static inline bool within_cpu_entry(unsigned long addr, unsigned long end) (unsigned long)&per_cpu(cpu_tss_rw, cpu), sizeof(struct tss_struct))) return true; + + /* + * cpu_tlbstate.user_pcid_flush_mask is used for CPU entry. + * If a data breakpoint on it, it will cause an unwanted #DB. + * Protect the full cpu_tlbstate structure to be sure. + */ + if (within_area(addr, end, + (unsigned long)&per_cpu(cpu_tlbstate, cpu), + sizeof(struct tlb_state))) + return true; } return false;
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