[PATCH AUTOSEL 4.4 12/17] xtensa: fix {get,put}_user() for 64bit values

Sasha Levin
2019-10-26T13:24:07Z

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

[ Upstream commit 6595d144decec396bf2e2efee27e50634a4b627f ]

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@zeniv.linux.org.uk>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
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 147b26ed9c91f..42133985a19a1 100644
--- a/arch/xtensa/include/asm/uaccess.h
+++ b/arch/xtensa/include/asm/uaccess.h
@@ -245,7 +245,7 @@ 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(); \
@@ -344,7 +344,16 @@ 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