Commit 246cd4b0 authored Nov 27, 2019 by Michael Ellerman Committed by Greg Kroah-Hartman Dec 17, 2019

powerpc: Define arch_is_kernel_initmem_freed() for lockdep



commit 6f07048c00fd100ed8cab66c225c157e0b6c0a50 upstream.

Under certain circumstances, we hit a warning in lockdep_register_key:

        if (WARN_ON_ONCE(static_obj(key)))
                return;

This occurs when the key falls into initmem that has since been freed
and can now be reused. This has been observed on boot, and under
memory pressure.

Define arch_is_kernel_initmem_freed(), which allows lockdep to
correctly identify this memory as dynamic.

This fixes a bug picked up by the powerpc64 syzkaller instance where
we hit the WARN via alloc_netdev_mqs.

Reported-by: Qian Cai <cai@lca.pw>
Reported-by: ppc syzbot c/o Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Daniel Axtens <dja@axtens.net>
Link: https://lore.kernel.org/r/87lfs4f7d6.fsf@dja-thinkpad.axtens.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 12de9bf4

arch/powerpc/include/asm/sections.h

+14 −0

Original line number	Diff line number	Diff line
		@@ -5,8 +5,22 @@

		#include <linux/elf.h>
		#include <linux/uaccess.h>

		#define arch_is_kernel_initmem_freed arch_is_kernel_initmem_freed

		#include <asm-generic/sections.h>

		extern bool init_mem_is_free;

		static inline int arch_is_kernel_initmem_freed(unsigned long addr)
		{
		if (!init_mem_is_free)
		return 0;

		return addr >= (unsigned long)__init_begin &&
		addr < (unsigned long)__init_end;
		}

		extern char __head_end[];

		#ifdef __powerpc64__