[PATCH] bugfix of access a invalid addr

[chenjie6]

From: chenjie <chenjie6@xxxxxxxxxx>

when we run fs_fsbase_t, some testcase like 
write05 failed 

write05     0  TINFO  :  Enter Block 1: test with bad fd
write05     1  TPASS  :  received EBADF as expected.
write05     0  TINFO  :  Exit Block 1
write05     0  TINFO  :  Enter Block 2: test with a bad address
write05     2  TFAIL  :  write() on an invalid buffer succeeded,
			 but should have failed

Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: chenjie <chenjie6@xxxxxxxxxx>

---
 fs/dax.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/dax.c b/fs/dax.c
index fc2e314..e1b1ff6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -214,6 +214,11 @@ static ssize_t dax_io(struct inode *inode, struct iov_iter *iter,
 			max = min(pos + size, end);
 		}
 
+		if (unlikely(iov_iter_fault_in_readable(iter, max - pos))) {
+			retval = -EFAULT;
+			break;
+		}
+
 		if (iov_iter_rw(iter) == WRITE) {
 			len = copy_from_iter_pmem(dax.addr, max - pos, iter);
 			need_wmb = true;
-- 
1.8.0