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genirq: Prevent NULL pointer dereference in resend_irqs() 

The following crash was observed:

  Unable to handle kernel NULL pointer dereference at 0000000000000158
  Internal error: Oops: 96000004 [#1] SMP
  pc : resend_irqs+0x68/0xb0
  lr : resend_irqs+0x64/0xb0
  ...
  Call trace:
   resend_irqs+0x68/0xb0
   tasklet_action_common.isra.6+0x84/0x138
   tasklet_action+0x2c/0x38
   __do_softirq+0x120/0x324
   run_ksoftirqd+0x44/0x60
   smpboot_thread_fn+0x1ac/0x1e8
   kthread+0x134/0x138
   ret_from_fork+0x10/0x18

The reason for this is that the interrupt resend mechanism happens in soft
interrupt context, which is a asynchronous mechanism versus other
operations on interrupts. free_irq() does not take resend handling into
account. Thus, the irq descriptor might be already freed before the resend
tasklet is executed. resend_irqs() does not check the return value of the
interrupt descriptor lookup and derefences the return value
unconditionally.

  1):
  __setup_irq
    irq_startup
      check_irq_resend  // activate softirq to handle resend irq
  2):
  irq_domain_free_irqs
    irq_free_descs
      free_desc
        call_rcu(&desc->rcu, delayed_free_desc)
  3):
  __do_softirq
    tasklet_action
      resend_irqs
        desc = irq_to_desc(irq)
        desc->handle_irq(desc)  // desc is NULL --> Ooops

Fix this by adding a NULL pointer check in resend_irqs() before derefencing
the irq descriptor.

Fixes: a4633adcdb ("[PATCH] genirq: add genirq sw IRQ-retrigger")
Signed-off-by: Yunfeng Ye <yeyunfeng@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Zhiqiang Liu <liuzhiqiang26@huawei.com>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1630ae13-5c8e-901e-de09-e740b6a426a7@huawei.com
This commit is contained in:
Yunfeng Ye 2019-09-04 20:46:25 +08:00 committed by Thomas Gleixner
parent 3b47fd5ca9
commit eddf3e9c7c
1 changed files with 2 additions and 0 deletions
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2
kernel/irq/resend.c
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@ -36,6 +36,8 @@ static void resend_irqs(unsigned long arg)
irq = find_first_bit(irqs_resend, nr_irqs); irq = find_first_bit(irqs_resend, nr_irqs);
clear_bit(irq, irqs_resend); clear_bit(irq, irqs_resend);
desc = irq_to_desc(irq); desc = irq_to_desc(irq);
if (!desc)
continue;
local_irq_disable(); local_irq_disable();
desc->handle_irq(desc); desc->handle_irq(desc);
local_irq_enable(); local_irq_enable();