memblock: introduce saner 'memblock_free_ptr()' interface

The boot-time allocation interface for memblock is a mess, with
'memblock_alloc()' returning a virtual pointer, but then you are
supposed to free it with 'memblock_free()' that takes a _physical_

Not only is that all kinds of strange and illogical, but it actually
causes bugs, when people then use it like a normal allocation function,
and it fails spectacularly on a NULL pointer:

or just random memory corruption if the debug checks don't catch it:

I really don't want to apply patches that treat the symptoms, when the
fundamental cause is this horribly confusing interface.

I started out looking at just automating a sane replacement sequence,
but because of this mix or virtual and physical addresses, and because
people have used the "__pa()" macro that can take either a regular
kernel pointer, or just the raw "unsigned long" address, it's all quite

So this just introduces a new saner interface for freeing a virtual
address that was allocated using 'memblock_alloc()', and that was kept
as a regular kernel pointer.  And then it converts a couple of users
that are obvious and easy to test, including the 'xbc_nodes' case in
lib/bootconfig.c that caused problems.

Reported-by: kernel test robot <>
Fixes: 40caa127f3c7 ("init: bootconfig: Remove all bootconfig data when the init memory is removed")
Cc: Steven Rostedt <>
Cc: Mike Rapoport <>
Cc: Andrew Morton <>
Cc: Ingo Molnar <>
Cc: Masami Hiramatsu <>
Cc: Vlastimil Babka <>
Signed-off-by: Linus Torvalds <>
11 files changed