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SubjectRe: [PATCH] x86/fpu: Fix invalid FPU ptrace state after execve
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 <yu-cheng.yu@intel.com>
> Reported-by: Robert O'Callahan <robert@ocallahan.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: David Hansen <dave.hansen@linux.intel.com>
> Cc: Fenghua Yu <fenghua.yu@intel.com>
> Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
> ---
> 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 != &current->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)
--

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