git.ipfire.org Git - thirdparty/kernel/stable-queue.git/blob

   1 From 9aece6f67af9059b4101bb91cfd20c65ba08d202 Mon Sep 17 00:00:00 2001
   2 From: Sasha Levin <sashal@kernel.org>
   3 Date: Sat, 3 Oct 2020 00:41:45 +0900
   4 Subject: can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard IRQ
   5  context
   6
   7 From: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
   8
   9 [ Upstream commit 2283f79b22684d2812e5c76fc2280aae00390365 ]
  10
  11 If a driver calls can_get_echo_skb() during a hardware IRQ (which is often, but
  12 not always, the case), the 'WARN_ON(in_irq)' in
  13 net/core/skbuff.c#skb_release_head_state() might be triggered, under network
  14 congestion circumstances, together with the potential risk of a NULL pointer
  15 dereference.
  16
  17 The root cause of this issue is the call to kfree_skb() instead of
  18 dev_kfree_skb_irq() in net/core/dev.c#enqueue_to_backlog().
  19
  20 This patch prevents the skb to be freed within the call to netif_rx() by
  21 incrementing its reference count with skb_get(). The skb is finally freed by
  22 one of the in-irq-context safe functions: dev_consume_skb_any() or
  23 dev_kfree_skb_any(). The "any" version is used because some drivers might call
  24 can_get_echo_skb() in a normal context.
  25
  26 The reason for this issue to occur is that initially, in the core network
  27 stack, loopback skb were not supposed to be received in hardware IRQ context.
  28 The CAN stack is an exeption.
  29
  30 This bug was previously reported back in 2017 in [1] but the proposed patch
  31 never got accepted.
  32
  33 While [1] directly modifies net/core/dev.c, we try to propose here a
  34 smoother modification local to CAN network stack (the assumption
  35 behind is that only CAN devices are affected by this issue).
  36
  37 [1] http://lore.kernel.org/r/57a3ffb6-3309-3ad5-5a34-e93c3fe3614d@cetitec.com
  38
  39 Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
  40 Link: https://lore.kernel.org/r/20201002154219.4887-2-mailhol.vincent@wanadoo.fr
  41 Fixes: 39549eef3587 ("can: CAN Network device driver and Netlink interface")
  42 Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
  43 Signed-off-by: Sasha Levin <sashal@kernel.org>
  44 ---
  45  drivers/net/can/dev.c | 6 +++++-
  46  1 file changed, 5 insertions(+), 1 deletion(-)
  47
  48 diff --git a/drivers/net/can/dev.c b/drivers/net/can/dev.c
  49 index 9dd968ee792e0..3c0f141262ad5 100644
  50 --- a/drivers/net/can/dev.c
  51 +++ b/drivers/net/can/dev.c
  52 @@ -466,7 +466,11 @@ unsigned int can_get_echo_skb(struct net_device *dev, unsigned int idx)
  53         if (!skb)
  54                 return 0;
  55
  56 -       netif_rx(skb);
  57 +       skb_get(skb);
  58 +       if (netif_rx(skb) == NET_RX_SUCCESS)
  59 +               dev_consume_skb_any(skb);
  60 +       else
  61 +               dev_kfree_skb_any(skb);
  62
  63         return len;
  64  }
  65 --
  66 2.27.0
  67