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cpumask: zero extra bits in alloc_cpumask_var_node

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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>
This commit is contained in:
Rusty Russell 2009-01-01 10:12:30 +10:30
parent 5db0e1e9e0
commit 2a53008033
1 changed files with 8 additions and 0 deletions
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8
lib/cpumask.c
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@ -107,6 +107,14 @@ bool alloc_cpumask_var_node(cpumask_var_t *mask, gfp_t flags, int node)
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);