3.16.78-rc1 review patch. If anyone has any objections, please let me know.
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From: Yunfeng Ye yeyunfeng@huawei.com
commit eddf3e9c7c7e4d0707c68d1bb22cc6ec8aef7d4a upstream.
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: a4633adcdbc1 ("[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 Link: https://lkml.kernel.org/r/1630ae13-5c8e-901e-de09-e740b6a426a7@huawei.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- kernel/irq/resend.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/kernel/irq/resend.c +++ b/kernel/irq/resend.c @@ -37,6 +37,8 @@ static void resend_irqs(unsigned long ar irq = find_first_bit(irqs_resend, nr_irqs); clear_bit(irq, irqs_resend); desc = irq_to_desc(irq); + if (!desc) + continue; local_irq_disable(); desc->handle_irq(irq, desc); local_irq_enable();