[PATCH] 2.5.44 Fix uninitialized device struct w/ add_disk()

[PATCH] 2.5.44 Fix uninitialized device struct w/ add_disk()

[Andres Salomon]

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This occurs w/ 2.5 device-mapper; add_disk() is called (w/ a possibly
invalid gendisk).  add_disk() calls register_disk(), which constructs
the device struct (gendisk::disk_dev).  First, the bus_id field is
initialized, and then device_add() is called.  However, device_add()
does no initialization of the device struct.  So, since the
gendisk::disk_dev::parent list is NULL, the gendisk::disk_dev::node
field is never initialized.  Later on in device_add(), if an error has
occurred, list_del_init(&dev->node) is called; dev->node is {NULL,NULL},
and an oops occurs.

Instead of calling device_add(), my patch makes register_disk() call
device_register().  This appear to do the same thing as device_add(),
but initializes the device struct before calling device_add().



-- 
It's not denial.  I'm just selective about the reality I accept.
	-- Bill Watterson

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--- a/fs/partitions/check.c	2002-10-19 03:56:00.000000000 -0400
+++ a/fs/partitions/check.c	2002-10-19 03:56:10.000000000 -0400
@@ -455,7 +455,7 @@
 	s = strchr(dev->bus_id, '/');
 	if (s)
 		*s = '!';
-	device_add(dev);
+	device_register(dev);
 	device_create_file(dev, &disk_attr_dev);
 	device_create_file(dev, &disk_attr_range);
 	device_create_file(dev, &disk_attr_size);

Re: [PATCH] 2.5.44 Fix uninitialized device struct w/ add_disk()

[Alexander Viro]

On Sat, 19 Oct 2002, Andres Salomon wrote:

> This occurs w/ 2.5 device-mapper; add_disk() is called (w/ a possibly
> invalid gendisk).  add_disk() calls register_disk(), which constructs
> the device struct (gendisk::disk_dev).  First, the bus_id field is
> initialized, and then device_add() is called.  However, device_add()
> does no initialization of the device struct.  So, since the
> gendisk::disk_dev::parent list is NULL, the gendisk::disk_dev::node
> field is never initialized.  Later on in device_add(), if an error has
> occurred, list_del_init(&dev->node) is called; dev->node is {NULL,NULL},
> and an oops occurs.
> 
> Instead of calling device_add(), my patch makes register_disk() call
> device_register().  This appear to do the same thing as device_add(),
> but initializes the device struct before calling device_add().

Wrong.  If device-mapper doesn't create gendisk with alloc_disk() - it's
their bug; if it does - initialization is already done at alloc_disk()
time.

Fix driver instead of breaking generic code.