Commit bac59d18 authored Jan 30, 2020 by Guenter Roeck Committed by Borislav Petkov Mar 19, 2020

x86/setup: Fix static memory detection



When booting x86 images in qemu, the following warning is seen randomly
if DEBUG_LOCKDEP is enabled.

  WARNING: CPU: 0 PID: 1 at kernel/locking/lockdep.c:1119
	  lockdep_register_key+0xc0/0x100

static_obj() returns true if an address is between _stext and _end.

On x86, this includes the brk memory space. Problem is that this memory
block is not static on x86; its unused portions are released after init
and can be allocated. This results in the observed warning if a lockdep
object is allocated from this memory.

Solve the problem by implementing arch_is_kernel_initmem_freed() for
x86 and have it return true if an address is within the released memory
range.

The same problem was solved for s390 with commit

  7a5da02d ("locking/lockdep: check for freed initmem in static_obj()"),

which introduced arch_is_kernel_initmem_freed().

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200131021159.9178-1-linux@roeck-us.net

parent 6f8f0dc9

arch/x86/include/asm/sections.h

+20 −0

Original line number	Diff line number	Diff line
		@@ -2,6 +2,8 @@
		#ifndef _ASM_X86_SECTIONS_H
		#define _ASM_X86_SECTIONS_H

		#define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed

		#include <asm-generic/sections.h>
		#include <asm/extable.h>

		@@ -14,4 +16,22 @@ extern char __end_rodata_hpage_align[];

		extern char __end_of_kernel_reserve[];

		extern unsigned long _brk_start, _brk_end;

		static inline bool arch_is_kernel_initmem_freed(unsigned long addr)
		{
		/*
		* If _brk_start has not been cleared, brk allocation is incomplete,
		* and we can not make assumptions about its use.
		*/
		if (_brk_start)
		return 0;

		/*
		* After brk allocation is complete, space between _brk_end and _end
		* is available for allocation.
		*/
		return addr >= _brk_end && addr < (unsigned long)&_end;
		}

		#endif /* _ASM_X86_SECTIONS_H */

arch/x86/kernel/setup.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -64,7 +64,6 @@ RESERVE_BRK(dmi_alloc, 65536);
		* at link time, with RESERVE_BRK*() facility reserving additional
		* chunks.
		*/
		static __initdata
		unsigned long _brk_start = (unsigned long)__brk_base;
		unsigned long _brk_end = (unsigned long)__brk_base;

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