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 <abaci@linux.alibaba.com>
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 6d7b12c..bf79f3a 100644 (file)
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -11,6 +11,7 @@
 #include <uapi/linux/pkt_sched.h>
 
 #define DEFAULT_TX_QUEUE_LEN   1000
+#define STAB_SIZE_LOG_MAX      30
 
 struct qdisc_walker {
        int     stop;

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 5e90e9b..12f39a2 100644 (file)
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -513,6 +513,12 @@ static struct qdisc_size_table *qdisc_get_stab(struct nlattr *opt,
                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);