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x86/hw_breakpoint: Prevent data breakpoints on user_pcid_flush_mask

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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@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas 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
This commit is contained in:
Lai Jiangshan 2020-05-29 23:27:32 +02:00 committed by Thomas Gleixner
parent f9fe0b89f0
commit fdef24dfcc
1 changed files with 11 additions and 0 deletions
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11
arch/x86/kernel/hw_breakpoint.c
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@ -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;