| Message ID | 20190607142915.y52mfmgk5lvhll7n@linutronix.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/fpu: Update kernel's FPU state before using for the fsave header | expand |
On Fri, Jun 07, 2019 at 04:29:16PM +0200, Sebastian Andrzej Siewior wrote: > In commit > > 39388e80f9b0c ("x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()") > > I removed the statement > | if (ia32_fxstate) > | copy_fxregs_to_kernel(fpu); > > and argued that is was wrongly merged because the content was already > saved in kernel's state and the content. > This was wrong: It is required to write it back because it is only saved > on the user-stack and save_fsave_header() reads it from task's > FPU-state. I missed that part… > > Save x87 FPU state unless thread's FPU registers are already up to date. > > Fixes: 39388e80f9b0c ("x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()") > Reported-by: Eric Biggers <ebiggers@kernel.org> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > arch/x86/kernel/fpu/signal.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > index 060d6188b4533..0071b794ed193 100644 > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -62,6 +62,11 @@ static inline int save_fsave_header(struct task_struct *tsk, void __user *buf) > struct user_i387_ia32_struct env; > struct _fpstate_32 __user *fp = buf; > > + fpregs_lock(); > + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) > + copy_fxregs_to_kernel(&tsk->thread.fpu); > + fpregs_unlock(); > + > convert_from_fxsr(&env, tsk); > > if (__copy_to_user(buf, &env, sizeof(env)) || > -- > 2.20.1 > Tested-by: Eric Biggers <ebiggers@kernel.org> - Eric
diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 060d6188b4533..0071b794ed193 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -62,6 +62,11 @@ static inline int save_fsave_header(struct task_struct *tsk, void __user *buf) struct user_i387_ia32_struct env; struct _fpstate_32 __user *fp = buf; + fpregs_lock(); + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) + copy_fxregs_to_kernel(&tsk->thread.fpu); + fpregs_unlock(); + convert_from_fxsr(&env, tsk); if (__copy_to_user(buf, &env, sizeof(env)) ||
In commit 39388e80f9b0c ("x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()") I removed the statement | if (ia32_fxstate) | copy_fxregs_to_kernel(fpu); and argued that is was wrongly merged because the content was already saved in kernel's state and the content. This was wrong: It is required to write it back because it is only saved on the user-stack and save_fsave_header() reads it from task's FPU-state. I missed that part… Save x87 FPU state unless thread's FPU registers are already up to date. Fixes: 39388e80f9b0c ("x86/fpu: Don't save fxregs for ia32 frames in copy_fpstate_to_sigframe()") Reported-by: Eric Biggers <ebiggers@kernel.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- arch/x86/kernel/fpu/signal.c | 5 +++++ 1 file changed, 5 insertions(+)