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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 <peterz@infradead.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Lai Jiangshan <jiangshanlai@gmail.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Link: https://lkml.kernel.org/r/20200505134058.272448010@linutronix.de
This commit is contained in:
Andy Lutomirski 2020-02-24 13:24:58 +01:00 committed by Thomas Gleixner
parent 1f1fbc70c1
commit 24ae0c91cb
1 changed files with 25 additions and 0 deletions
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25
arch/x86/kernel/hw_breakpoint.c
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@ -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;