From b22cbe404a9cc3c7949e380fa1861e31934c8978 Mon Sep 17 00:00:00 2001 From: Yu-cheng Yu Date: Thu, 17 Nov 2016 09:11:35 -0800 Subject: [PATCH] x86/fpu: Fix invalid FPU ptrace state after execve() 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 fpu__clear() does not properly clear fpstate. Fix it by doing just that. Reported-by: Robert O'Callahan Signed-off-by: Yu-cheng Yu Cc: Cc: Andy Lutomirski Cc: Borislav Petkov Cc: David Hansen Cc: Fenghua Yu Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Ravi V. Shankar Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1479402695-6553-1-git-send-email-yu-cheng.yu@intel.com Signed-off-by: Ingo Molnar --- 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 47004010ad5d..ebb4e95fbd74 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); + + /* + * Make sure fpstate is cleared and initialized. + */ + if (static_cpu_has(X86_FEATURE_FPU)) { + fpu__activate_curr(fpu); + user_fpu_begin(); copy_init_fpstate_to_fpregs(); } } -- 2.20.1