[PATCH v3 3/4] x86/fpu: Fix __user annotations

[Jann Horn]

In save_xstate_epilog(), use __user when type-casting userspace pointers.

In setup_sigcontext() and x32_setup_rt_frame(), cast the userspace
pointers to 'unsigned long __user *' before writing into them.
These pointers are originally '__u32 __user *' or '__u64 __user *',
causing sparse to complain when a userspace pointer is written into
them. The casts are okay because the pointers always point to
pointer-sized values.
Thanks to Luc Van Oostenryck and Al Viro for explaining this to me.

Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
---
 arch/x86/kernel/fpu/signal.c | 6 +++---
 arch/x86/kernel/signal.c     | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c
index f6a1d299627c..55b80de13ea5 100644
--- a/arch/x86/kernel/fpu/signal.c
+++ b/arch/x86/kernel/fpu/signal.c
@@ -92,13 +92,13 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
 		return err;
 
 	err |= __put_user(FP_XSTATE_MAGIC2,
-			  (__u32 *)(buf + fpu_user_xstate_size));
+			  (__u32 __user *)(buf + fpu_user_xstate_size));
 
 	/*
 	 * Read the xfeatures which we copied (directly from the cpu or
 	 * from the state in task struct) to the user buffers.
 	 */
-	err |= __get_user(xfeatures, (__u32 *)&x->header.xfeatures);
+	err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
 
 	/*
 	 * For legacy compatible, we always set FP/SSE bits in the bit
@@ -113,7 +113,7 @@ static inline int save_xstate_epilog(void __user *buf, int ia32_frame)
 	 */
 	xfeatures |= XFEATURE_MASK_FPSSE;
 
-	err |= __put_user(xfeatures, (__u32 *)&x->header.xfeatures);
+	err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures);
 
 	return err;
 }
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 08dfd4c1a4f9..b419e1a1a0ce 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -206,7 +206,7 @@ int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
 		put_user_ex(regs->ss, &sc->ss);
 #endif /* CONFIG_X86_32 */
 
-		put_user_ex(fpstate, &sc->fpstate);
+		put_user_ex(fpstate, (unsigned long __user *)&sc->fpstate);
 
 		/* non-iBCS2 extensions.. */
 		put_user_ex(mask, &sc->oldmask);
@@ -569,7 +569,7 @@ static int x32_setup_rt_frame(struct ksignal *ksig,
 			restorer = NULL;
 			err |= -EFAULT;
 		}
-		put_user_ex(restorer, &frame->pretcode);
+		put_user_ex(restorer, (unsigned long __user *)&frame->pretcode);
 	} put_user_catch(err);
 
 	err |= setup_sigcontext(&frame->uc.uc_mcontext, fpstate,
-- 
2.21.0.392.gf8f6787159e-goog