[PATCH 3.10 082/319] asm-generic: make get_user() clear the destination on errors

From: Willy Tarreau
Date: Sun Feb 05 2017 - 14:27:13 EST


From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

commit 9ad18b75c2f6e4a78ce204e79f37781f8815c0fa upstream.

both for access_ok() failures and for faults halfway through

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Willy Tarreau <w@xxxxxx>
---
include/asm-generic/uaccess.h | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index c184aa8..fee282a 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -228,14 +228,18 @@ extern int __put_user_bad(void) __attribute__((noreturn));
might_sleep(); \
access_ok(VERIFY_READ, ptr, sizeof(*ptr)) ? \
__get_user(x, ptr) : \
- -EFAULT; \
+ ((x) = (__typeof__(*(ptr)))0,-EFAULT); \
})

#ifndef __get_user_fn
static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
{
- size = __copy_from_user(x, ptr, size);
- return size ? -EFAULT : size;
+ size_t n = __copy_from_user(x, ptr, size);
+ if (unlikely(n)) {
+ memset(x + (size - n), 0, n);
+ return -EFAULT;
+ }
+ return 0;
}

#define __get_user_fn(sz, u, k) __get_user_fn(sz, u, k)
--
2.8.0.rc2.1.gbe9624a