On Wed, Nov 16, 2016 at 08:56:36AM -0800, Yu-cheng Yu wrote:
> Robert O'Callahan reported that after an execve PTRACE_GETREGSET
> NT_X86_XSTATE continues to return the pre-exec register values
> until the exec'ed task modifies FPU state. The test code is at
> https://bugzilla.redhat.com/attachment.cgi?id=1164286.
>
> What is happening is when eagerfpu is enabled, fpu__clear() did
> not properly clear fpstate. Fix it by doing just that.
>
> Signed-off-by: Yu-cheng Yu <[email protected]>
> Reported-by: Robert O'Callahan <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: David Hansen <[email protected]>
> Cc: Fenghua Yu <[email protected]>
> Cc: "Ravi V. Shankar" <[email protected]>
> ---
> arch/x86/kernel/fpu/core.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
> index 4700401..4c203c4 100644
> --- a/arch/x86/kernel/fpu/core.c
> +++ b/arch/x86/kernel/fpu/core.c
> @@ -521,14 +521,14 @@ void fpu__clear(struct fpu *fpu)
> {
> WARN_ON_FPU(fpu != ¤t->thread.fpu); /* Almost certainly an
> anomaly */
>
> - if (!use_eager_fpu() || !static_cpu_has(X86_FEATURE_FPU)) {
> - /* FPU state will be reallocated lazily at the first use. */
> - fpu__drop(fpu);
> - } else {
> - if (!fpu->fpstate_active) {
> - fpu__activate_curr(fpu);
> - user_fpu_begin();
> - }
> + fpu__drop(fpu);
> +
> + /*
> + * When eagerfpu is used, make sure fpstate is cleared and initialized.
> + */
> + if (use_eager_fpu()) {
c592b5734706 ("x86/fpu: Remove use_eager_fpu()")
Please redo this patch against tip/master.
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284
(AG Nürnberg)
--
