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| author |   Thomas Gleixner <tglx@linutronix.de> | 2016-12-13 19:32:28 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2016-12-15 11:32:31 +0100 |
| commit | 427d77a32365d5f942d335248305a5c237baf63a (patch) | |
| tree | bc71ce672cf89239bdd90b15a1a5e39e2123fa10 /include/linux/cpumask.h | |
| parent | x86/boot/64: Push correct start_cpu() return address (diff) | |
| download | linux-dev-427d77a32365d5f942d335248305a5c237baf63a.tar.xz linux-dev-427d77a32365d5f942d335248305a5c237baf63a.zip | |
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 <dsafonov@virtuozzo.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: 0x7f454c46@gmail.com
Cc: Jan Beulich <JBeulich@novell.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.20.1612131836050.3415@nanos
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/linux/cpumask.h')
| -rw-r--r-- | include/linux/cpumask.h | 5 |
1 files changed, 5 insertions, 0 deletions
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) { |