Subject: Re: arch/powerpc/radix: Fix kernel crash with mremap

From: Michael Ellerman <[email-masked]>
Date: Tue, 5 Feb 2019 22:25:45 +1100 (AEDT)

On Wed, 2019-01-23 at 06:21:38 UTC, "Aneesh Kumar K.V" wrote:
> With support for split pmd lock, we use pmd page pmd_huge_pte pointer to store
> the deposited page table. In those config when we move page tables we need to
> make sure we move the depoisted page table to the right pmd page. Otherwise this
> can result in crash when we withdraw of deposited page table because we can find
> the pmd_huge_pte NULL.
> 
> c0000000004a1230 __split_huge_pmd+0x1070/0x1940
> c0000000004a0ff4 __split_huge_pmd+0xe34/0x1940 (unreliable)
> c0000000004a4000 vma_adjust_trans_huge+0x110/0x1c0
> c00000000042fe04 __vma_adjust+0x2b4/0x9b0
> c0000000004316e8 __split_vma+0x1b8/0x280
> c00000000043192c __do_munmap+0x13c/0x550
> c000000000439390 sys_mremap+0x220/0x7e0
> c00000000000b488 system_call+0x5c/0x70
> 
> Fixes: 675d995297d4 ("powerpc/book3s64: Enable split pmd ptlock.")
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>
> Signed-off-by: Aneesh Kumar K.V <[email-masked]>

Applied to powerpc fixes, thanks.

https://git.kernel.org/powerpc/c/579b9239c1f38665b21e8d0e6ee83ecc

cheers