rps: fix insufficient bounds checking in store_rps_dev_flow_table_cnt()

Setting a large rps_flow_cnt like (1 << 30) on 32-bit platform will
cause a kernel oops due to insufficient bounds checking.

	if (count > 1<<30) {
		/* Enforce a limit to prevent overflow */
		return -EINVAL;
	}
	count = roundup_pow_of_two(count);
	table = vmalloc(RPS_DEV_FLOW_TABLE_SIZE(count));

Note that the macro RPS_DEV_FLOW_TABLE_SIZE(count) is defined as:

	... + (count * sizeof(struct rps_dev_flow))

where sizeof(struct rps_dev_flow) is 8.  (1 << 30) * 8 will overflow
32 bits.

This patch replaces the magic number (1 << 30) with a symbolic bound.

Suggested-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Xi Wang <xi.wang@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index c71c434a4c053e440dc816682d944c521e05c50f..385aefe536489548ed3f53e61094faaac0d08afd 100644 (file)
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -665,11 +665,14 @@ static ssize_t store_rps_dev_flow_table_cnt(struct netdev_rx_queue *queue,
        if (count) {
                int i;
 
-               if (count > 1<<30) {
+               if (count > INT_MAX)
+                       return -EINVAL;
+               count = roundup_pow_of_two(count);
+               if (count > (ULONG_MAX - sizeof(struct rps_dev_flow_table))
+                               / sizeof(struct rps_dev_flow)) {
                        /* Enforce a limit to prevent overflow */
                        return -EINVAL;
                }
-               count = roundup_pow_of_two(count);
                table = vmalloc(RPS_DEV_FLOW_TABLE_SIZE(count));
                if (!table)
                        return -ENOMEM;