netdev - [Question] integer overflow in function __qdisc_calculate_pkt

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Message-ID: <7723cc01-57bf-2b64-7f78-98a0e6508a2e@huawei.com>
Date: Fri, 2 Jun 2023 10:50:44 +0800
From: "luwei (O)" <luwei32@...wei.com>
To: Networking <netdev@...r.kernel.org>
Subject: [Question] integer overflow in function __qdisc_calculate_pkt_len()

Hi list,

     I found an integer overflow issue in function 
__qdisc_calculate_pkt_len(), the root cause is overhead and cell_align 
in stab is not checked.

For example, if overhead is set to -2147483559 and cell_align is set to 
-32767 (tc tool limit it to 0 and -1, but other values can be set with 
netlink api),

the integer overflow occurs:

  568 void __qdisc_calculate_pkt_len(struct sk_buff *skb,
  569                                const struct qdisc_size_table *stab)
  570 {
  571         int pkt_len, slot;
  572
  573         pkt_len = skb->len + stab->szopts.overhead; (1)
  574         if (unlikely(!stab->szopts.tsize))
  575                 goto out;
  576
  577         slot = pkt_len + stab->szopts.cell_align;   (2)
  578         if (unlikely(slot < 0))
  579                 slot = 0;

if skb->len is 66, slot will be 66 + (-2147483559) + (-32767) = 
2147451036, and pkt_len will be 2147451040 finally.  I think the value 
of overhead and cell_align

should be limited, but not sure to which values they should be limited, 
can any one give me some suggestions?








-- 
Best Regards,
Lu Wei