linux-kernel - [tip:x86/urgent] x86/ioapic: Fix incorrect pointers in ioapic_setup

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Date:	Fri, 10 Jun 2016 05:48:52 -0700
From:	tip-bot for Rui Wang <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	rui.y.wang@...el.com, tglx@...utronix.de, mingo@...nel.org,
	linux-kernel@...r.kernel.org, hpa@...or.com
Subject: [tip:x86/urgent] x86/ioapic: Fix incorrect pointers in
 ioapic_setup_resources()

Commit-ID:  9d98bcec731756b8688b59ec998707924d716d7b
Gitweb:     http://git.kernel.org/tip/9d98bcec731756b8688b59ec998707924d716d7b
Author:     Rui Wang <rui.y.wang@...el.com>
AuthorDate: Wed, 8 Jun 2016 14:59:52 +0800
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Fri, 10 Jun 2016 14:45:54 +0200

x86/ioapic: Fix incorrect pointers in ioapic_setup_resources()

On a 4-socket Brickland system, hot-removing one ioapic is fine.
Hot-removing the 2nd one causes panic in mp_unregister_ioapic()
while calling release_resource().

It is because the iomem_res pointer has already been released
when removing the first ioapic.

To explain the use of &res[num] here: res is assigned to ioapic_resources,
and later in ioapic_insert_resources() we do:

	struct resource *r = ioapic_resources;

        for_each_ioapic(i) {
                insert_resource(&iomem_resource, r);
                r++;
        }

Here 'r' is treated as an arry of 'struct resource', and the r++ ensures
that each element of the array is inserted separately. Thus we should call
release_resouce() on each element at &res[num].

Fix it by assigning the correct pointers to ioapics[i].iomem_res in
ioapic_setup_resources().

Signed-off-by: Rui Wang <rui.y.wang@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: tony.luck@...el.com
Cc: linux-pci@...r.kernel.org
Cc: rjw@...ysocki.net
Cc: linux-acpi@...r.kernel.org
Cc: bhelgaas@...gle.com
Link: http://lkml.kernel.org/r/1465369193-4816-3-git-send-email-rui.y.wang@intel.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/kernel/apic/io_apic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c
index 84e33ff..446702e 100644
--- a/arch/x86/kernel/apic/io_apic.c
+++ b/arch/x86/kernel/apic/io_apic.c
@@ -2588,8 +2588,8 @@ static struct resource * __init ioapic_setup_resources(void)
 		res[num].flags = IORESOURCE_MEM | IORESOURCE_BUSY;
 		snprintf(mem, IOAPIC_RESOURCE_NAME_SIZE, "IOAPIC %u", i);
 		mem += IOAPIC_RESOURCE_NAME_SIZE;
+		ioapics[i].iomem_res = &res[num];
 		num++;
-		ioapics[i].iomem_res = res;
 	}
 
 	ioapic_resources = res;