Commit fe0c52fc authored Jan 26, 2015 by Marc Zyngier Committed by Thomas Gleixner Apr 08, 2015

genirq: MSI: Fix freeing of unallocated MSI



While debugging an unrelated issue with the GICv3 ITS driver, the
following trace triggered:

WARNING: CPU: 1 PID: 1 at kernel/irq/irqdomain.c:1121 irq_domain_free_irqs+0x160/0x17c()
NULL pointer, cannot free irq
Modules linked in:
CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W      3.19.0-rc6+ #3690
Hardware name: FVP Base (DT)
Call trace:
[<ffffffc000089398>] dump_backtrace+0x0/0x13c
[<ffffffc0000894e4>] show_stack+0x10/0x1c
[<ffffffc00066d134>] dump_stack+0x74/0x94
[<ffffffc0000a92f8>] warn_slowpath_common+0x9c/0xd4
[<ffffffc0000a938c>] warn_slowpath_fmt+0x5c/0x80
[<ffffffc0000ee04c>] irq_domain_free_irqs+0x15c/0x17c
[<ffffffc0000ef918>] msi_domain_free_irqs+0x58/0x74
[<ffffffc000386f58>] free_msi_irqs+0xb4/0x1c0

    // The msi_prepare callback fails here

[<ffffffc0003872c0>] pci_enable_msix+0x25c/0x3d4
[<ffffffc00038746c>] pci_enable_msix_range+0x34/0x80
[<ffffffc0003924ac>] vp_try_to_find_vqs+0xec/0x528
[<ffffffc000392954>] vp_find_vqs+0x6c/0xa8
[<ffffffc0003ee2a8>] init_vq+0x120/0x248
[<ffffffc0003eefb0>] virtblk_probe+0xb0/0x6bc
[<ffffffc00038fc34>] virtio_dev_probe+0x17c/0x214
[<ffffffc0003d4a04>] driver_probe_device+0x7c/0x23c
[<ffffffc0003d4cb0>] __driver_attach+0x98/0xa0
[<ffffffc0003d2c60>] bus_for_each_dev+0x60/0xb4
[<ffffffc0003d455c>] driver_attach+0x1c/0x28
[<ffffffc0003d41b0>] bus_add_driver+0x150/0x208
[<ffffffc0003d54c0>] driver_register+0x64/0x130
[<ffffffc00038f9e8>] register_virtio_driver+0x24/0x68
[<ffffffc00091320c>] init+0x70/0xac
[<ffffffc0000828f0>] do_one_initcall+0x94/0x1d0
[<ffffffc0008e9b00>] kernel_init_freeable+0x144/0x1e4
[<ffffffc00066a434>] kernel_init+0xc/0xd8
---[ end trace f9ee562a77cc7bae ]---

The ITS msi_prepare callback having failed, we end-up trying to
free MSIs that have never been allocated. Oddly enough, the kernel
is pretty upset about it.

It turns out that this behaviour was expected before the MSI domain
was introduced (and dealt with in arch_teardown_msi_irqs).

The obvious fix is to detect this early enough and bail out.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Reviewed-by: Jiang Liu <jiang.liu@linux.intel.com>
Link: http://lkml.kernel.org/r/1422299419-6051-1-git-send-email-marc.zyngier@arm.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 462b69b1

kernel/irq/msi.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -310,10 +310,17 @@ void msi_domain_free_irqs(struct irq_domain domain, struct device dev)
		struct msi_desc *desc;

		for_each_msi_entry(desc, dev) {
		/*
		* We might have failed to allocate an MSI early
		* enough that there is no IRQ associated to this
		* entry. If that's the case, don't do anything.
		*/
		if (desc->irq) {
		irq_domain_free_irqs(desc->irq, desc->nvec_used);
		desc->irq = 0;
		}
		}
		}

		/**
		* msi_get_domain_info - Get the MSI interrupt domain info for @domain

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