Commit b22cbe40 authored Nov 17, 2016 by Yu-cheng Yu Committed by Ingo Molnar Nov 21, 2016

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 <robert@ocallahan.org>
Signed-off-by: Yu-cheng Yu <yu-cheng.yu@intel.com>
Cc: <stable@vger.kernel.org>
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: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi V. Shankar <ravi.v.shankar@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1479402695-6553-1-git-send-email-yu-cheng.yu@intel.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent ed68d7e9

arch/x86/kernel/fpu/core.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -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) {

		/*
		* 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();
		}
		}