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authorAl Viro <viro@ZenIV.linux.org.uk>2016-09-20 22:07:42 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-21 02:44:28 +0300
commite23d4159b109167126e5bcd7f3775c95de7fee47 (patch)
tree15a9480da60c53b2754ed8aa6cf57dab92e9df65 /include/linux/pagemap.h
parentdf04abfd181acc276ba6762c8206891ae10ae00d (diff)
downloadlinux-e23d4159b109167126e5bcd7f3775c95de7fee47.tar.xz
fix fault_in_multipages_...() on architectures with no-op access_ok()
Switching iov_iter fault-in to multipages variants has exposed an old bug in underlying fault_in_multipages_...(); they break if the range passed to them wraps around. Normally access_ok() done by callers will prevent such (and it's a guaranteed EFAULT - ERR_PTR() values fall into such a range and they should not point to any valid objects). However, on architectures where userland and kernel live in different MMU contexts (e.g. s390) access_ok() is a no-op and on those a range with a wraparound can reach fault_in_multipages_...(). Since any wraparound means EFAULT there, the fix is trivial - turn those while (uaddr <= end) ... into if (unlikely(uaddr > end)) return -EFAULT; do ... while (uaddr <= end); Reported-by: Jan Stancek <jstancek@redhat.com> Tested-by: Jan Stancek <jstancek@redhat.com> Cc: stable@vger.kernel.org # v3.5+ Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/pagemap.h')
-rw-r--r--include/linux/pagemap.h38
1 files changed, 19 insertions, 19 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 66a1260b33de..7e3d53753612 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -571,56 +571,56 @@ static inline int fault_in_pages_readable(const char __user *uaddr, int size)
*/
static inline int fault_in_multipages_writeable(char __user *uaddr, int size)
{
- int ret = 0;
char __user *end = uaddr + size - 1;
if (unlikely(size == 0))
- return ret;
+ return 0;
+ if (unlikely(uaddr > end))
+ return -EFAULT;
/*
* Writing zeroes into userspace here is OK, because we know that if
* the zero gets there, we'll be overwriting it.
*/
- while (uaddr <= end) {
- ret = __put_user(0, uaddr);
- if (ret != 0)
- return ret;
+ do {
+ if (unlikely(__put_user(0, uaddr) != 0))
+ return -EFAULT;
uaddr += PAGE_SIZE;
- }
+ } while (uaddr <= end);
/* Check whether the range spilled into the next page. */
if (((unsigned long)uaddr & PAGE_MASK) ==
((unsigned long)end & PAGE_MASK))
- ret = __put_user(0, end);
+ return __put_user(0, end);
- return ret;
+ return 0;
}
static inline int fault_in_multipages_readable(const char __user *uaddr,
int size)
{
volatile char c;
- int ret = 0;
const char __user *end = uaddr + size - 1;
if (unlikely(size == 0))
- return ret;
+ return 0;
- while (uaddr <= end) {
- ret = __get_user(c, uaddr);
- if (ret != 0)
- return ret;
+ if (unlikely(uaddr > end))
+ return -EFAULT;
+
+ do {
+ if (unlikely(__get_user(c, uaddr) != 0))
+ return -EFAULT;
uaddr += PAGE_SIZE;
- }
+ } while (uaddr <= end);
/* Check whether the range spilled into the next page. */
if (((unsigned long)uaddr & PAGE_MASK) ==
((unsigned long)end & PAGE_MASK)) {
- ret = __get_user(c, end);
- (void)c;
+ return __get_user(c, end);
}
- return ret;
+ return 0;
}
int add_to_page_cache_locked(struct page *page, struct address_space *mapping,