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>
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@ -107,6 +107,14 @@ bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
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dump_stack();
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}
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#endif
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/* FIXME: Bandaid to save us from old primitives which go to NR_CPUS. */
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if (*mask) {
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unsigned int tail;
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tail = BITS_TO_LONGS(NR_CPUS - nr_cpumask_bits) * sizeof(long);
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memset(cpumask_bits(*mask) + cpumask_size() - tail,
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0, tail);
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}
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return *mask != NULL;
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}
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EXPORT_SYMBOL(alloc_cpumask_var_node);
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