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powerpc: Define arch_is_kernel_initmem_freed() for lockdep

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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
This commit is contained in:
Michael Ellerman 2019-11-27 18:41:26 +11:00
parent 8dcd71b45d
commit 6f07048c00
1 changed files with 14 additions and 0 deletions
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14
arch/powerpc/include/asm/sections.h
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@ -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__