From 427d77a32365d5f942d335248305a5c237baf63a Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 13 Dec 2016 19:32:28 +0100 Subject: x86/smpboot: Prevent false positive out of bounds cpumask access warning prefill_possible_map() reinitializes the cpu_possible_map by setting the possible cpu bits and clearing all other bits up to NR_CPUS. This is technically always correct because cpu_possible_map is statically allocated and sized NR_CPUS. With CPUMASK_OFFSTACK and DEBUG_PER_CPU_MAPS enabled the bounds check of cpu masks happens on nr_cpu_ids. nr_cpu_ids is initialized to NR_CPUS and only limited after the set/clear bit loops have been executed. But if the system was booted with "nr_cpus=N" on the command line, where N is < NR_CPUS then nr_cpu_ids is limited in the parameter parsing function before prefill_possible_map() is invoked. As a consequence the cpumask bounds check triggers when clearing the bits past nr_cpu_ids. Add a helper which allows to reset cpu_possible_map w/o the bounds check and then set only the possible bits which are well inside bounds. Reported-by: Dmitry Safonov Cc: Rusty Russell Cc: 0x7f454c46@gmail.com Cc: Jan Beulich Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1612131836050.3415@nanos Signed-off-by: Thomas Gleixner --- include/linux/cpumask.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include/linux/cpumask.h') diff --git a/include/linux/cpumask.h b/include/linux/cpumask.h index da7fbf1cdd56..c717f5ea88cb 100644 --- a/include/linux/cpumask.h +++ b/include/linux/cpumask.h @@ -722,6 +722,11 @@ void init_cpu_present(const struct cpumask *src); void init_cpu_possible(const struct cpumask *src); void init_cpu_online(const struct cpumask *src); +static inline void reset_cpu_possible_mask(void) +{ + bitmap_zero(cpumask_bits(&__cpu_possible_mask), NR_CPUS); +} + static inline void set_cpu_possible(unsigned int cpu, bool possible) { -- cgit v1.2.3-59-g8ed1b