[PATCH 4.4 41/57] x86/fpu: Reset state for all signal restore failures

[Sasha Levin]

From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>

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@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/87mtryyhhz.ffs@xxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 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 8fc842dae3b3..9a1489b92782 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -262,15 +262,23 @@ 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