[PATCH v5sub1 7/8] arm64: move kernel image to base of vmalloc area

[Ard Biesheuvel]

On 12 February 2016 at 16:10, Catalin Marinas <catalin.marinas at arm.com> wrote:
> On Fri, Feb 12, 2016 at 04:02:58PM +0100, Ard Biesheuvel wrote:
>> On 12 February 2016 at 15:58, Catalin Marinas <catalin.marinas at arm.com> wrote:
>> > Hi Ard,
>> >
>> > On Mon, Feb 01, 2016 at 11:54:52AM +0100, Ard Biesheuvel wrote:
>> >> This moves the module area to right before the vmalloc area, and
>> >> moves the kernel image to the base of the vmalloc area. This is
>> >> an intermediate step towards implementing KASLR, which allows the
>> >> kernel image to be located anywhere in the vmalloc area.
>> >>
>> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
>> >
>> > This patch is causing lots of KASAN warnings on Juno (interestingly, it
>> > doesn't seem to trigger on Seattle, though we only tried for-next/core).
>> > I pushed the branch that I'm currently using here:
>> >
>> > git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux for-next/kernmap
>> >
>> >
>> > A typical error (though its place varies based on the config options,
>> > kernel layout):
>> >
>> > BUG: KASAN: stack-out-of-bounds in clockevents_program_event+0x28/0x1b0 at addr ffffffc936257cc8
>>
>> Can you confirm that these are stack accesses? I was having similar
>> errors before, and I ended up creating the kasan zero page patch
>> because it turned out the kasan shadow page in question was aliased
>> and the stack writes were occurring elsewhere.
>
> It's possible, we are looking into this. Is there any other patch I miss on
> the above branch?
>

I don't think so but I will check

> BTW, disabling CPU_IDLE, I get other errors:
>
> WARNING: at /work/Linux/linux-2.6-aarch64/mm/vmalloc.c:135
> Modules linked in:
>

Since this occurs in kasan_module_alloc(), I think this may be a
symptom of the same underlying issue, where the kernel VA space and
the projection onto the Kasan shadow area are somehow out of sync.

I will try to reproduce with the branch above.



> CPU: 2 PID: 973 Comm: systemd-modules Tainted: G        W       4.5.0-rc1+ #131
> Hardware name: Juno (DT)
> task: ffffffc93448e200 ti: ffffffc9346ac000 task.ti: ffffffc9346ac000
> PC is at vmap_page_range_noflush+0x240/0x2e8
> LR is at vmap_page_range_noflush+0x16c/0x2e8
> pc : [<ffffff90041fef78>] lr : [<ffffff90041feea4>] pstate: 20000145
> sp : ffffffc9346af9b0
> x29: ffffffc9346af9b0 x28: ffffff90050da000
> x27: ffffffc001438008 x26: ffffffbde6d16440
> x25: 0000004240000000 x24: ffffffc97ff3a000
> x23: 0000000000000041 x22: ffffffc078e9e600
> x21: ffffff8200002000 x20: ffffff8200001000
> x19: 0000000000000000 x18: 00000000f3294c2f
> x17: 00000000f7dc90fb x16: 0000000087b402ce
> x15: ffffffffffffffff x14: ffffff0000000000
> x13: ffffffffffffffff x12: 0000000000000028
> x11: 0101010101010101 x10: 00000001801a001a
> x9 : 0000000000000000 x8 : ffffff89268b2400
> x7 : 0000000000000000 x6 : 000000000000003f
> x5 : 0000000000000040 x4 : 0000000000000000
> x3 : 0000000000000000 x2 : 1ffffff800287001
> x1 : dfffff9000000000 x0 : 00e8000081439713
>
> ---[ end trace 8a78d7ad8d08d2a9 ]---
> Call trace:
> Exception stack(0xffffffc9346af790 to 0xffffffc9346af8b0)
> f780:                                   0000000000000000 ffffff8200001000
> f7a0: ffffffc9346af9b0 ffffff90041fef78 0000000020000145 000000000000003d
> f7c0: 0000004240000000 ffffffc078e9f600 0000000041b58ab3 ffffff9004f0c370
> f7e0: ffffff9004082608 ffffffc078e9f620 00000000024080c2 0000000000400000
> f800: ffffffc9346afe70 ffffffc9346afe50 ffffffc9346af9b0 ffffffc93448e200
> f820: ffffffc9346af830 ffffff900408b1b0 ffffffc9346af900 ffffff900408b228
> f840: ffffffc9346ac000 ffffffc9346af9b0 ffffffc9346ac000 ffffffc078e9e600
> f860: 0000000041b58ab3 ffffff9004f0c8a8 ffffff900408b080 000000010010000e
> f880: ffffffc9346af9b0 0000000000000000 00e8000081439713 dfffff9000000000
> f8a0: 1ffffff800287001 0000000000000000
> [<ffffff90041fef78>] vmap_page_range_noflush+0x240/0x2e8
> [<ffffff90041ff078>] map_vm_area+0x58/0x88
> [<ffffff9004200400>] __vmalloc_node_range+0x2b8/0x350
> [<ffffff9004224394>] kasan_module_alloc+0x64/0xb8
> [<ffffff90040943f4>] module_alloc+0x5c/0xa0
> [<ffffff9004169460>] load_module+0x1798/0x3098
> [<ffffff900416b020>] SyS_finit_module+0xf8/0x108
> [<ffffff9004085d30>] el0_svc_naked+0x24/0x28
> vmalloc: allocation failure, allocated 4096 of 4096 bytes
>
> --
> Catalin