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authorThomas Gleixner <tglx@linutronix.de>2017-12-23 19:45:11 +0100
committerThomas Gleixner <tglx@linutronix.de>2017-12-23 20:18:42 +0100
commitf6c4fd506cb626e4346aa81688f255e593a7c5a0 (patch)
tree51356ab92d31c42e817b02ded05fe2dad0d17a81
parent613e396bc0d4c7604fba23256644e78454c68cf6 (diff)
downloadlinux-f6c4fd506cb626e4346aa81688f255e593a7c5a0.tar.bz2
x86/cpu_entry_area: Prevent wraparound in setup_cpu_entry_area_ptes() on 32bit
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>
-rw-r--r--arch/x86/mm/cpu_entry_area.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c
index 21e8b595cbb1..fe814fd5e014 100644
--- 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_ptes(void)
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
}