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| author | Lai Jiangshan <laijs@linux.alibaba.com> | 2021-02-04 23:27:07 +0800 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2021-02-05 20:13:12 +0100 |
| commit | 3943abf2dbfae9ea4d2da05c1db569a0603f76da (patch) | |
| tree | 36182b39ffc8b5ad40e4985c999665c8b5e26956 /arch/x86/kernel/hw_breakpoint.c | |
| parent | c4bed4b96918ff1d062ee81fdae4d207da4fa9b0 (diff) | |
| download | lwn-3943abf2dbfae9ea4d2da05c1db569a0603f76da.tar.gz lwn-3943abf2dbfae9ea4d2da05c1db569a0603f76da.zip | |
x86/debug: Prevent data breakpoints on cpu_dr7
local_db_save() is called at the start of exc_debug_kernel(), reads DR7 and
disables breakpoints to prevent recursion.
When running in a guest (X86_FEATURE_HYPERVISOR), local_db_save() reads the
per-cpu variable cpu_dr7 to check whether a breakpoint is active or not
before it accesses DR7.
A data breakpoint on cpu_dr7 therefore results in infinite #DB recursion.
Disallow data breakpoints on cpu_dr7 to prevent that.
Fixes: 84b6a3491567a("x86/entry: Optimize local_db_save() for virt")
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210204152708.21308-2-jiangshanlai@gmail.com
Diffstat (limited to 'arch/x86/kernel/hw_breakpoint.c')
| -rw-r--r-- | arch/x86/kernel/hw_breakpoint.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index 012ed82e5bd3..668a4a6533d9 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -307,6 +307,14 @@ static inline bool within_cpu_entry(unsigned long addr, unsigned long end) (unsigned long)&per_cpu(cpu_tlbstate, cpu), sizeof(struct tlb_state))) return true; + + /* + * When in guest (X86_FEATURE_HYPERVISOR), local_db_save() + * will read per-cpu cpu_dr7 before clear dr7 register. + */ + if (within_area(addr, end, (unsigned long)&per_cpu(cpu_dr7, cpu), + sizeof(cpu_dr7))) + return true; } return false; |