set_mempolicy() and mbind() take as argument a pointer to a bit mask (nodemask) and the number of bits in the mask the kernel will use (maxnode), among others. For instace on a system with 2 NUMA nodes valid masks are: 0b00, 0b01, 0b10 and 0b11 it's clear maxnode=2, however an off-by-one error in get_nodes() the function that copies the node mask from user space requires users to pass maxnode = 3 in this example and maxnode = actual_maxnode + 1 in the general case. This patch fixes such error.
Signed-off-by: Luis Felipe Sandoval Castro <[email protected]> --- mm/mempolicy.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 006ba62..0c2e3cd 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -1265,11 +1265,10 @@ static int get_nodes(nodemask_t *nodes, const unsigned long __user *nmask, unsigned long nlongs; unsigned long endmask; - --maxnode; nodes_clear(*nodes); - if (maxnode == 0 || !nmask) + if (maxnode == 1 || !nmask) return 0; - if (maxnode > PAGE_SIZE*BITS_PER_BYTE) + if (maxnode - 1 > PAGE_SIZE * BITS_PER_BYTE) return -EINVAL; nlongs = BITS_TO_LONGS(maxnode); -- 1.8.3.1
