[PATCH 4.9 49/71] x86/fpu: Reset state for all signal restore failures

Sasha Levin
2021-06-28T15:21:22Z

From: Thomas Gleixner <tglx@linutronix.de>

commit efa165504943f2128d50f63de0c02faf6dcceb0d upstream.

If access_ok() or fpregs_soft_set() fails in __fpu__restore_sig() then the
function just returns but does not clear the FPU state as it does for all
other fatal failures.

Clear the FPU state for these failures as well.

Fixes: 72a671ced66d ("x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/87mtryyhhz.ffs@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/fpu/signal.c | 18 +++++++++++++-----
1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index 769831d9fd11..07b0ebd49576 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -276,15 +276,23 @@ static int __fpu__restore_sig(void __user *buf, void __user *buf_fx, int size)
return 0;
}

- if (!access_ok(VERIFY_READ, buf, size))
+ if (!access_ok(VERIFY_READ, buf, size)) {
+ fpu__clear(fpu);
return -EACCES;
+ }

fpu__activate_curr(fpu);

- if (!static_cpu_has(X86_FEATURE_FPU))
- return fpregs_soft_set(current, NULL,
- 0, sizeof(struct user_i387_ia32_struct),
- NULL, buf) != 0;
+ if (!static_cpu_has(X86_FEATURE_FPU)) {
+ int ret = fpregs_soft_set(current, NULL, 0,
+ sizeof(struct user_i387_ia32_struct),
+ NULL, buf);
+
+ if (ret)
+ fpu__clear(fpu);
+
+ return ret != 0;
+ }

if (use_xsave()) {
struct _fpx_sw_bytes fx_sw_user;
--
2.30.2