4.19-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit 1ca4fa3ab604734e38e2a3000c9abf788512ffa7 ]
register_sched_domain_sysctl() copies the cpu_possible_mask into sd_sysctl_cpus, but only if sd_sysctl_cpus hasn't already been allocated (ie, CONFIG_CPUMASK_OFFSTACK is set). However, when CONFIG_CPUMASK_OFFSTACK is not set, sd_sysctl_cpus is left uninitialized (all zeroes) and the kernel may fail to initialize sched_domain sysctl entries for all possible CPUs.
This is visible to the user if the kernel is booted with maxcpus=n, or if ACPI tables have been modified to leave CPUs offline, and then checking for missing /proc/sys/kernel/sched_domain/cpu* entries.
Fix this by separating the allocation and initialization, and adding a flag to initialize the possible CPU entries while system booting only.
Tested-by: Syuuichirou Ishii ishii.shuuichir@jp.fujitsu.com Tested-by: Tarumizu, Kohei tarumizu.kohei@jp.fujitsu.com Signed-off-by: Hidetoshi Seto seto.hidetoshi@jp.fujitsu.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Masayoshi Mizuma m.mizuma@jp.fujitsu.com Acked-by: Joe Lawrence joe.lawrence@redhat.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Masayoshi Mizuma msys.mizuma@gmail.com Cc: Mike Galbraith efault@gmx.de Cc: Peter Zijlstra peterz@infradead.org Cc: Thomas Gleixner tglx@linutronix.de Link: https://lkml.kernel.org/r/20190129151245.5073-1-msys.mizuma@gmail.com Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/debug.c | 4 ++++ 1 file changed, 4 insertions(+)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 6383aa6a60ca..141ea9ff210e 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -315,6 +315,7 @@ void register_sched_domain_sysctl(void) { static struct ctl_table *cpu_entries; static struct ctl_table **cpu_idx; + static bool init_done = false; char buf[32]; int i;
@@ -344,7 +345,10 @@ void register_sched_domain_sysctl(void) if (!cpumask_available(sd_sysctl_cpus)) { if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL)) return; + }
+ if (!init_done) { + init_done = true; /* init to possible to not have holes in @cpu_entries */ cpumask_copy(sd_sysctl_cpus, cpu_possible_mask); }