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SubjectRe: [tip:x86/mm] [x86/mm] b389949485: WARNING:at_arch/x86/mm/pat/set_memory.c:#__change_page_attr
On Sun, Nov 06, 2022 at 08:38:27PM +0800, kernel test robot wrote:
>
> Greeting,
>
> FYI, we noticed WARNING:at_arch/x86/mm/pat/set_memory.c:#__change_page_attr due to commit (built with gcc-11):
>
> commit: b38994948567e6d6b62947401c57f4ab2efe070c ("x86/mm: Implement native set_memory_rox()")
> https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git x86/mm
>
> [test failed on linux-next/master 0cdb3579f1ee4c1e55acf8dfb0697b660067b1f8]
>
> in testcase: boot
>
> on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>
> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>
>
> If you fix the issue, kindly add following tag
> | Reported-by: kernel test robot <oliver.sang@intel.com>
> | Link: https://lore.kernel.org/oe-lkp/202211061748.eb591682-oliver.sang@intel.com
>
>
> [ 44.943065][ T11] ------------[ cut here ]------------
> [ 44.943725][ T11] CPA detected W^X violation: 0000000000000060 -> 0000000000000063 range: 0xffff8881beca5000 - 0xffff8881beca5fff PFN 1beca5
> [ 44.944929][ T11] WARNING: CPU: 0 PID: 11 at arch/x86/mm/pat/set_memory.c:609 __change_page_attr (arch/x86/mm/pat/set_memory.c:609 arch/x86/mm/pat/set_memory.c:1582)
> [ 44.945824][ T11] Modules linked in:
> [ 44.946229][ T11] CPU: 0 PID: 11 Comm: kworker/0:1 Tainted: G W 6.1.0-rc3-00010-gb38994948567 #1 f37474c2082f37dd433f70907b94c2b0df8d70b8
> [ 44.947518][ T11] Workqueue: events bpf_prog_free_deferred
> [ 44.948074][ T11] RIP: 0010:__change_page_attr (arch/x86/mm/pat/set_memory.c:609 arch/x86/mm/pat/set_memory.c:1582)

Urgh, as spotted by dhansen, the code in change_page_attr_set_clr(),
specifically the checkalias thing, seems to rely on single bit flips for
NX.

Let me try to make sense of this stuff....

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