linux-kernel - [PATCH v3 1/3] xtensa: fix {get,put}

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Message-Id: <20191014212513.17661-2-jcmvbkbc@gmail.com>
Date:   Mon, 14 Oct 2019 14:25:11 -0700
From:   Max Filippov <jcmvbkbc@...il.com>
To:     linux-xtensa@...ux-xtensa.org, Al Viro <viro@...iv.linux.org.uk>
Cc:     Chris Zankel <chris@...kel.net>, linux-kernel@...r.kernel.org,
        Max Filippov <jcmvbkbc@...il.com>
Subject: [PATCH v3 1/3] xtensa: fix {get,put}_user() for 64bit values

From: Al Viro <viro@...iv.linux.org.uk>

First of all, on short copies __copy_{to,from}_user() return the amount
of bytes left uncopied, *not* -EFAULT.  get_user() and put_user() are
expected to return -EFAULT on failure.

Another problem is get_user(v32, (__u64 __user *)p); that should
fetch 64bit value and the assign it to v32, truncating it in process.
Current code, OTOH, reads 8 bytes of data and stores them at the
address of v32, stomping on the 4 bytes that follow v32 itself.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Max Filippov <jcmvbkbc@...il.com>
---
 arch/xtensa/include/asm/uaccess.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/xtensa/include/asm/uaccess.h b/arch/xtensa/include/asm/uaccess.h
index 6792928ba84a..f568c00392ec 100644
--- a/arch/xtensa/include/asm/uaccess.h
+++ b/arch/xtensa/include/asm/uaccess.h
@@ -100,7 +100,7 @@ do {									\
 	case 4: __put_user_asm(x, ptr, retval, 4, "s32i", __cb); break;	\
 	case 8: {							\
 		     __typeof__(*ptr) __v64 = x;			\
-		     retval = __copy_to_user(ptr, &__v64, 8);		\
+		     retval = __copy_to_user(ptr, &__v64, 8) ? -EFAULT : 0;	\
 		     break;						\
 	        }							\
 	default: __put_user_bad();					\
@@ -198,7 +198,16 @@ do {									\
 	case 1: __get_user_asm(x, ptr, retval, 1, "l8ui", __cb);  break;\
 	case 2: __get_user_asm(x, ptr, retval, 2, "l16ui", __cb); break;\
 	case 4: __get_user_asm(x, ptr, retval, 4, "l32i", __cb);  break;\
-	case 8: retval = __copy_from_user(&x, ptr, 8);    break;	\
+	case 8: {							\
+		u64 __x;						\
+		if (unlikely(__copy_from_user(&__x, ptr, 8))) {		\
+			retval = -EFAULT;				\
+			(x) = 0;					\
+		} else {						\
+			(x) = *(__force __typeof__((ptr)))&__x;		\
+		}							\
+		break;							\
+	}								\
 	default: (x) = __get_user_bad();				\
 	}								\
 } while (0)
-- 
2.20.1