Commit fdef24df authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Thomas Gleixner
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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: default avatarLai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200526014221.2119-5-laijs@linux.alibaba.com
Link: https://lkml.kernel.org/r/20200529213320.955117574@infradead.org
parent f9fe0b89

arch/x86/kernel/hw_breakpoint.c

+11 −0
Original line number Diff line number Diff line
@@ -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;