Patch "x86/ioapic: Fix incorrect pointers in ioapic_setup_resources()" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

x86/ioapic: Fix incorrect pointers in ioapic_setup_resources()

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
x86-ioapic-fix-incorrect-pointers-in-ioapic_setup_resources.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Rui Wang <[email protected]>
Date: Wed, 8 Jun 2016 14:59:52 +0800
Subject: x86/ioapic: Fix incorrect pointers in ioapic_setup_resources()

From: Rui Wang <[email protected]>

commit 9d98bcec731756b8688b59ec998707924d716d7b upstream.

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().

---
 arch/x86/kernel/apic/io_apic.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -2592,8 +2592,8 @@ static struct resource * __init ioapic_s
 		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;

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/x86-ioapic-fix-incorrect-pointers-in-ioapic_setup_resources.patch