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>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index c71c434a4c05..385aefe53648 100644
--- 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;