cpumask: zero extra bits in alloc_cpumask_var_node
Impact: extra safety checks during transition
When CONFIG_CPUMASKS_OFFSTACK is set, the new cpumask_ operators only
use bits up to nr_cpu_ids, not NR_CPUS. Using the old cpus_ operators
on these masks can mean accessing undefined bits.
After some discussion, Mike and I decided to err on the side of caution;
we zero the "undefined" bits in alloc_cpumask_var_node() until all the
old cpumask functions are removed.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/lib/cpumask.c b/lib/cpumask.c
index 8e1496c..3389e24 100644
--- a/lib/cpumask.c
+++ b/lib/cpumask.c
@@ -107,6 +107,14 @@
dump_stack();
}
#endif
+ /* FIXME: Bandaid to save us from old primitives which go to NR_CPUS. */
+ if (*mask) {
+ unsigned int tail;
+ tail = BITS_TO_LONGS(NR_CPUS - nr_cpumask_bits) * sizeof(long);
+ memset(cpumask_bits(*mask) + cpumask_size() - tail,
+ 0, tail);
+ }
+
return *mask != NULL;
}
EXPORT_SYMBOL(alloc_cpumask_var_node);