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Unsigned integer overflow in batadv_iv_ogm_calc_tq

Message ID 1792155.rcBUdH4UUQ@bentobox (mailing list archive)
State RFC, archived
Commit 789b846af6a9471982b181687a1cba8dc996b269
Headers

Commit Message

Sven Eckelmann Feb. 15, 2016, 12:35 p.m. UTC 
  Hi,

just ran my emulation setup [1] and got an integer overflow (undefined behavior):

    ================================================================================
    UBSAN: Undefined behaviour in /home/sven/tmp/qemu-batman/batman-adv/net/batman-adv/bat_iv_ogm.c:1246:25
    signed integer overflow:
    8713350 * 255 cannot be represented in type 'int'
    CPU: 1 PID: 0 Comm: swapper/1 Tainted: G           O    4.5.0-rc4-next-20160215 #10
    Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
     1ffff10001980ea7 10e2f8880f23fbe1 ffff88000cc075b0 ffffffff817f196f
     0000000041b58ab3 ffffffff824b0b5f ffffffff817f1894 ffff88000cc075d8
     ffff88000cc07588 ffff88000cc075a0 00000000000000ff ffff88000cc07398
    Call Trace:
     <IRQ>  [<ffffffff817f196f>] dump_stack+0xdb/0x15c
     [<ffffffff817f1894>] ? _atomic_dec_and_lock+0xc4/0xc4
     [<ffffffff8186c21b>] ubsan_epilogue+0xd/0x8a
     [<ffffffff8186dbba>] handle_overflow+0x211/0x260
     [<ffffffff8186d9a9>] ? __ubsan_handle_negate_overflow+0x1b1/0x1b1
     [<ffffffff811ebd6d>] ? trace_hardirqs_on+0xd/0x10
     [<ffffffffa0041ed0>] ? batadv_neigh_ifinfo_get+0x330/0x330 [batman_adv]
     [<ffffffffa0008390>] ? batadv_iv_ogm_process_per_outif+0x1380/0x33f0 [batman_adv]
     [<ffffffff811ebd6d>] ? trace_hardirqs_on+0xd/0x10
     [<ffffffff8186dc37>] __ubsan_handle_mul_overflow+0xe/0x17
     [<ffffffffa0009d74>] batadv_iv_ogm_process_per_outif+0x2d64/0x33f0 [batman_adv]
     [<ffffffffa0007f27>] ? batadv_iv_ogm_process_per_outif+0xf17/0x33f0 [batman_adv]
     [<ffffffffa000acd4>] batadv_iv_ogm_receive+0x8d4/0x1d20 [batman_adv]
     [<ffffffffa000a7c2>] ? batadv_iv_ogm_receive+0x3c2/0x1d20 [batman_adv]
     [<ffffffffa0037468>] batadv_batman_skb_recv+0x378/0x490 [batman_adv]
     [<ffffffffa00370f0>] ? batadv_skb_set_priority+0x640/0x640 [batman_adv]
     [<ffffffff81c68577>] __netif_receive_skb_core+0x7b7/0x2a50
     [<ffffffff81c67dc0>] ? __skb_csum_offload_chk+0x12a0/0x12a0
     [<ffffffff81c6f215>] __netif_receive_skb+0x55/0x200
     [<ffffffff81c6f4b9>] netif_receive_skb_internal+0xf9/0x3e0
     [<ffffffff81c6f454>] ? netif_receive_skb_internal+0x94/0x3e0
     [<ffffffff81c6f3c0>] ? __netif_receive_skb+0x200/0x200
     [<ffffffff81c71bce>] ? dev_gro_receive+0x76e/0x1ca0
     [<ffffffff81c71a6c>] ? dev_gro_receive+0x60c/0x1ca0
     [<ffffffff81c32331>] ? __netdev_alloc_skb+0x1d1/0x350
     [<ffffffff813ec1a6>] ? memcpy+0x36/0x40
     [<ffffffff81ce34b0>] ? eth_commit_mac_addr_change+0x70/0x70
     [<ffffffff81acc2f4>] ? page_to_skb+0x1d4/0x720
     [<ffffffff81c7321a>] napi_gro_receive+0x11a/0x240
     [<ffffffff81ad2564>] virtnet_receive+0xc14/0x26b0
     [<ffffffff81ad1950>] ? try_fill_recv+0x1530/0x1530
     [<ffffffff810cbe70>] ? pvclock_read_flags+0x6d0/0x6d0
     [<ffffffff8185bd80>] ? __list_add+0x3f0/0x3f0
     [<ffffffff81ad437d>] virtnet_poll+0x1d/0x160
     [<ffffffff81c70e63>] net_rx_action+0x6a3/0xca0
     [<ffffffff812183ed>] ? handle_irq_event+0xcd/0x1a0
     [<ffffffff81223245>] ? handle_fasteoi_irq+0x275/0x8f0
     [<ffffffff810fa930>] ? __do_softirq+0x1d0/0x870
     [<ffffffff810fa9e8>] __do_softirq+0x288/0x870
     [<ffffffff810fb263>] irq_exit+0xe3/0x140
     [<ffffffff8102209e>] do_IRQ+0x9e/0x200
     [<ffffffff8216fdcc>] common_interrupt+0x8c/0x8c
     <EOI>  [<ffffffff810c9a66>] ? native_safe_halt+0x6/0x10
     [<ffffffff811ebd6d>] ? trace_hardirqs_on+0xd/0x10
     [<ffffffff810364de>] default_idle+0xe/0x20
     [<ffffffff8103774a>] arch_cpu_idle+0xa/0x10
     [<ffffffff811d199f>] default_idle_call+0x4f/0x80
     [<ffffffff811d1c94>] cpu_startup_entry+0x2c4/0x540
     [<ffffffff8216eb76>] ? _raw_spin_unlock_irqrestore+0x36/0x60
     [<ffffffff811d19d0>] ? default_idle_call+0x80/0x80
     [<ffffffff8126f5b8>] ? clockevents_register_device+0xf8/0x1f0
     [<ffffffff810a9f9b>] start_secondary+0x35b/0x4c0
     [<ffffffff810a9c40>] ? set_cpu_sibling_map+0x2fe0/0x2fe0
    ================================================================================

The code is:

	combined_tq = batadv_ogm_packet->tq *
		      tq_own *
		      tq_asym_penalty *
		      tq_iface_penalty;
	combined_tq /= BATADV_TQ_MAX_VALUE *
		       BATADV_TQ_MAX_VALUE *
		       BATADV_TQ_MAX_VALUE;

It is easy to see that

    batadv_ogm_packet::tq (u8 255) *
    tq_own (u8 255) *
    tq_asym_penalty (int 134) *
    tq_iface_penalty (int 255)

is outside the range of an signed integer (32 bit). The maximum seen
here is 255 for each entry. So should tq_iface_penalty +
tq_iface_penalty, inv_asym_penalty be changed to unsigned int?


Kind regards,
	Sven



[1] https://www.open-mesh.org/projects/open-mesh/wiki/Emulation_Debug

Comments

Antonio Quartulli Feb. 20, 2016, 5:10 a.m. UTC | #1 
On Mon, Feb 15, 2016 at 01:35:31PM +0100, Sven Eckelmann wrote:
> It is easy to see that
> 
>     batadv_ogm_packet::tq (u8 255) *
>     tq_own (u8 255) *
>     tq_asym_penalty (int 134) *
>     tq_iface_penalty (int 255)
> 
> is outside the range of an signed integer (32 bit). The maximum seen
> here is 255 for each entry. So should tq_iface_penalty +
> tq_iface_penalty, inv_asym_penalty be changed to unsigned int?

Given that all these values are in the TQ domain I'd say that they should all be
positive all the time, therefore there is no gain in using a signed variable
here.

Marek, what do you think ?

Cheers,
diff mbox

Patch

--- a/net/batman-adv/bat_iv_ogm.c
+++ b/net/batman-adv/bat_iv_ogm.c
@@ -1147,9 +1147,10 @@  static int batadv_iv_ogm_calc_tq(struct batadv_orig_node *orig_node,
 	u8 total_count;
 	u8 orig_eq_count, neigh_rq_count, neigh_rq_inv, tq_own;
 	unsigned int neigh_rq_inv_cube, neigh_rq_max_cube;
-	int tq_asym_penalty, inv_asym_penalty, if_num, ret = 0;
+	int if_num, ret = 0;
+	unsigned int tq_asym_penalty, inv_asym_penalty;
 	unsigned int combined_tq;
-	int tq_iface_penalty;
+	unsigned int tq_iface_penalty;
 
 	/* find corresponding one hop neighbor */
 	rcu_read_lock();