net: prevent user from passing illegal stab size

We observed below report when playing with netlink sock:

UBSAN: shift-out-of-bounds in net/sched/sch_api.c:580:10
shift exponent 249 is too large for 32-bit type
CPU: 0 PID: 685 Comm: a.out Not tainted
Call Trace:
dump_stack_lvl+0x8d/0xcf
ubsan_epilogue+0xa/0x4e
__ubsan_handle_shift_out_of_bounds+0x161/0x182
__qdisc_calculate_pkt_len+0xf0/0x190
__dev_queue_xmit+0x2ed/0x15b0

it seems like kernel won't check the stab log value passing from
user, and will use the insane value later to calculate pkt_len.

This patch just add a check on the size/cell_log to avoid insane
calculation.

Reported-by: Abaci <[e-mail]>
Signed-off-by: Michael Wang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/net/pkt_sched.h

···
 #include <uapi/linux/pkt_sched.h>
 
 #define DEFAULT_TX_QUEUE_LEN	1000
+#define STAB_SIZE_LOG_MAX	30
 
 struct qdisc_walker {
 	int	stop;

net/sched/sch_api.c

···
 		return stab;
 	}
 
+	if (s->size_log > STAB_SIZE_LOG_MAX ||
+	    s->cell_log > STAB_SIZE_LOG_MAX) {
+		NL_SET_ERR_MSG(extack, "Invalid logarithmic size of size table");
+		return ERR_PTR(-EINVAL);
+	}
+
 	stab = kmalloc(sizeof(*stab) + tsize * sizeof(u16), GFP_KERNEL);
 	if (!stab)
 		return ERR_PTR(-ENOMEM);