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    SubjectRe: [PATCH 4.9 086/104] arm64: kasan: avoid bad virt_to_pfn()
    Hi Greg,

    On Fri, Oct 06, 2017 at 10:52:04AM +0200, Greg Kroah-Hartman wrote:
    > 4.9-stable review patch. If anyone has any objections, please let me know.

    I'm a little confused as to why this is being backported, given it
    wasn't Cc'd stable or marked as a fix.

    The lm_alias() helper was only introduced in v4.10, and I don't recall
    seeing that backported.

    What's going on here?

    Thanks,
    Mark.

    >
    > ------------------
    >
    > From: Mark Rutland <mark.rutland@arm.com>
    >
    >
    > [ Upstream commit b0de0ccc8b9edd8846828e0ecdc35deacdf186b0 ]
    >
    > Booting a v4.11-rc1 kernel with DEBUG_VIRTUAL and KASAN enabled produces
    > the following splat (trimmed for brevity):
    >
    > [ 0.000000] virt_to_phys used for non-linear address: ffff200008080000 (0xffff200008080000)
    > [ 0.000000] WARNING: CPU: 0 PID: 0 at arch/arm64/mm/physaddr.c:14 __virt_to_phys+0x48/0x70
    > [ 0.000000] PC is at __virt_to_phys+0x48/0x70
    > [ 0.000000] LR is at __virt_to_phys+0x48/0x70
    > [ 0.000000] Call trace:
    > [ 0.000000] [<ffff2000080b1ac0>] __virt_to_phys+0x48/0x70
    > [ 0.000000] [<ffff20000a03b86c>] kasan_init+0x1c0/0x498
    > [ 0.000000] [<ffff20000a034018>] setup_arch+0x2fc/0x948
    > [ 0.000000] [<ffff20000a030c68>] start_kernel+0xb8/0x570
    > [ 0.000000] [<ffff20000a0301e8>] __primary_switched+0x6c/0x74
    >
    > This is because we use virt_to_pfn() on a kernel image address when
    > trying to figure out its nid, so that we can allocate its shadow from
    > the same node.
    >
    > As with other recent changes, this patch uses lm_alias() to solve this.
    >
    > We could instead use NUMA_NO_NODE, as x86 does for all shadow
    > allocations, though we'll likely want the "real" memory shadow to be
    > backed from its corresponding nid anyway, so we may as well be
    > consistent and find the nid for the image shadow.
    >
    > Cc: Catalin Marinas <catalin.marinas@arm.com>
    > Cc: Will Deacon <will.deacon@arm.com>
    > Acked-by: Laura Abbott <labbott@redhat.com>
    > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
    > Signed-off-by: Will Deacon <will.deacon@arm.com>
    > Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
    > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > ---
    > arch/arm64/mm/kasan_init.c | 2 +-
    > 1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > --- a/arch/arm64/mm/kasan_init.c
    > +++ b/arch/arm64/mm/kasan_init.c
    > @@ -153,7 +153,7 @@ void __init kasan_init(void)
    > clear_pgds(KASAN_SHADOW_START, KASAN_SHADOW_END);
    >
    > vmemmap_populate(kimg_shadow_start, kimg_shadow_end,
    > - pfn_to_nid(virt_to_pfn(_text)));
    > + pfn_to_nid(virt_to_pfn(lm_alias(_text))));
    >
    > /*
    > * vmemmap_populate() has populated the shadow region that covers the
    >
    >

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