On 2021-01-25 at 10:39, Greg Kroah-Hartman wrote:
From: Andy Lutomirski luto@kernel.org
commit 67de8dca50c027ca0fa3b62a488ee5035036a0da upstream.
The default kernel_fpu_begin() doesn't work on systems that support XMM but haven't yet enabled CR4.OSFXSR. This causes crashes when _mmx_memcpy() is called too early because LDMXCSR generates #UD when the aforementioned bit is clear.
Fix it by using kernel_fpu_begin_mask(KFPU_387) explicitly.
Fixes: 7ad816762f9b ("x86/fpu: Reset MXCSR to default in kernel_fpu_begin()") Reported-by: Krzysztof Mazur krzysiek@podlesie.net Signed-off-by: Andy Lutomirski luto@kernel.org Signed-off-by: Borislav Petkov bp@suse.de Tested-by: Krzysztof Piotr Olędzki ole@ans.pl Tested-by: Krzysztof Mazur krzysiek@podlesie.net Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/e7bf21855fe99e5f3baa27446e32623358f69e8d.161120569... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
Similar to 5.10.11, we also need https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... in 5.4.93:
Otherwise, the kernel will fail to compile if CONFIG_X86_USE_3DNOW=y
arch/x86/lib/mmx_32.c: In function '_mmx_memcpy': arch/x86/lib/mmx_32.c:50:2: error: implicit declaration of function 'kernel_fpu_begin_mask'; did you mean 'kernel_fpu_begin'? [-Werror=implicit-function-declaration] 50 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~~~~~~~~~~~~~~ | kernel_fpu_begin arch/x86/lib/mmx_32.c:50:24: error: 'KFPU_387' undeclared (first use in this function) 50 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~ arch/x86/lib/mmx_32.c:50:24: note: each undeclared identifier is reported only once for each function it appears in arch/x86/lib/mmx_32.c: In function 'fast_clear_page': arch/x86/lib/mmx_32.c:140:24: error: 'KFPU_387' undeclared (first use in this function) 140 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~ arch/x86/lib/mmx_32.c: In function 'fast_copy_page': arch/x86/lib/mmx_32.c:173:24: error: 'KFPU_387' undeclared (first use in this function) 173 | kernel_fpu_begin_mask(KFPU_387); | ^~~~~~~~
Thanks, Krzysztof