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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 /arch | |
| parent | 31dcfec11f827e9a5d8720fe4728f1305894884f (diff) | |
| download | linux-427d77a32365d5f942d335248305a5c237baf63a.tar.bz2 | |
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 'arch')
| -rw-r--r-- | arch/x86/kernel/smpboot.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index e09aa58a7603..46732dc3b73c 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -1463,15 +1463,15 @@ __init void prefill_possible_map(void) possible = i; } + nr_cpu_ids = possible; + pr_info("Allowing %d CPUs, %d hotplug CPUs\n", possible, max_t(int, possible - num_processors, 0)); + reset_cpu_possible_mask(); + for (i = 0; i < possible; i++) set_cpu_possible(i, true); - for (; i < NR_CPUS; i++) - set_cpu_possible(i, false); - - nr_cpu_ids = possible; } #ifdef CONFIG_HOTPLUG_CPU |