[PATCH 1/2] powerpc: Fix user data corruption with P9N DD2.1 VSX CI load workaround emulation

[Michael Ellerman]

On Tue, 13 Oct 2020 15:37:40 +1100, Michael Neuling wrote:
> __get_user_atomic_128_aligned() stores to kaddr using stvx which is a
> VMX store instruction, hence kaddr must be 16 byte aligned otherwise
> the store won't occur as expected.
> 
> Unfortunately when we call __get_user_atomic_128_aligned() in
> p9_hmi_special_emu(), the buffer we pass as kaddr (ie. vbuf) isn't
> guaranteed to be 16B aligned. This means that the write to vbuf in
> __get_user_atomic_128_aligned() has the bottom bits of the address
> truncated. This results in other local variables being
> overwritten. Also vbuf will not contain the correct data which results
> in the userspace emulation being wrong and hence user data corruption.
> 
> [...]

Applied to powerpc/fixes.

[1/2] powerpc: Fix undetected data corruption with P9N DD2.1 VSX CI load emulation
      https://git.kernel.org/powerpc/c/1da4a0272c5469169f78cd76cf175ff984f52f06
[2/2] selftests/powerpc: Make alignment handler test P9N DD2.1 vector CI load workaround
      https://git.kernel.org/powerpc/c/d1781f23704707d350b8c9006e2bdf5394bf91b2

cheers