Messages in this thread Patch in this message | | | From | Ingo Molnar <> | Subject | [PATCH 175/208] x86/fpu: Clean up fpu__clear() state handling | Date | Tue, 5 May 2015 19:57:59 +0200 |
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We currently leak FPU state across execve() boundaries on eagerfpu systems:
$ /host/home/mingo/dump-xmm-regs-exec # XMM state before execve(): XMM0 : 000000000000dede XMM1 : 000000000000dedf XMM2 : 000000000000dee0 XMM3 : 000000000000dee1 XMM4 : 000000000000dee2 XMM5 : 000000000000dee3 XMM6 : 000000000000dee4 XMM7 : 000000000000dee5 XMM8 : 000000000000dee6 XMM9 : 000000000000dee7 XMM10: 000000000000dee8 XMM11: 000000000000dee9 XMM12: 000000000000deea XMM13: 000000000000deeb XMM14: 000000000000deec XMM15: 000000000000deed
# XMM state after execve(), in the new task context: XMM0 : 0000000000000000 XMM1 : 2f2f2f2f2f2f2f2f XMM2 : 0000000000000000 XMM3 : 0000000000000000 XMM4 : 00000000000000ff XMM5 : 00000000ff000000 XMM6 : 000000000000dee4 XMM7 : 000000000000dee5 XMM8 : 0000000000000000 XMM9 : 0000000000000000 XMM10: 0000000000000000 XMM11: 0000000000000000 XMM12: 0000000000000000 XMM13: 000000000000deeb XMM14: 000000000000deec XMM15: 000000000000deed
The reason is that fpu__clear() does not clear out the state properly.
Fix it.
Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> --- arch/x86/kernel/fpu/core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 45ef4e51928b..33c9a43b000e 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -348,6 +348,10 @@ void fpu__restore(void) } EXPORT_SYMBOL_GPL(fpu__restore); +/* + * Called by sys_execve() to clear the FPU fpregs, so that FPU state + * of the previous binary does not leak over into the exec()ed binary: + */ void fpu__clear(struct task_struct *tsk) { struct fpu *fpu = &tsk->thread.fpu; @@ -361,8 +365,8 @@ void fpu__clear(struct task_struct *tsk) if (!fpu->fpstate_active) { fpu__activate_curr(fpu); user_fpu_begin(); - restore_init_xstate(); } + restore_init_xstate(); } } -- 2.1.0
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