| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.14 32/74] x86/cpu_entry_area: Prevent wraparound in setup_cpu_entry_area_ptes() on 32bit | Date | Wed, 27 Dec 2017 17:46:05 +0100 |
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4.14-stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner <tglx@linutronix.de>
commit f6c4fd506cb626e4346aa81688f255e593a7c5a0 upstream.
The loop which populates the CPU entry area PMDs can wrap around on 32bit machines when the number of CPUs is small.
It worked wonderful for NR_CPUS=64 for whatever reason and the moron who wrote that code did not bother to test it with !SMP.
Check for the wraparound to fix it.
Fixes: 92a0f81d8957 ("x86/cpu_entry_area: Move it out of the fixmap") Reported-by: kernel test robot <fengguang.wu@intel.com> Signed-off-by: Thomas "Feels stupid" Gleixner <tglx@linutronix.de> Tested-by: Borislav Petkov <bp@alien8.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/x86/mm/cpu_entry_area.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -122,7 +122,8 @@ static __init void setup_cpu_entry_area_ start = CPU_ENTRY_AREA_BASE; end = start + CPU_ENTRY_AREA_MAP_SIZE; - for (; start < end; start += PMD_SIZE) + /* Careful here: start + PMD_SIZE might wrap around */ + for (; start < end && start >= CPU_ENTRY_AREA_BASE; start += PMD_SIZE) populate_extra_pte(start); #endif }
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