AIO: properly check iovec sizes

In Linus's tree, the iovec code has been reworked massively, but in
older kernels the AIO layer should be checking this before passing the
request on to other layers.

Many thanks to Ben Hawkes of Google Project Zero for pointing out the
issue.

Reported-by: Ben Hawkes <hawkes@google.com>
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Tested-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index 3241659491b1b80e78d133b04444c79b507dc0fe..0612022162ad4b18ad74d340643581e276da0fac 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1375,11 +1375,16 @@ static ssize_t aio_setup_single_vector(struct kiocb *kiocb,
                                       unsigned long *nr_segs,
                                       struct iovec *iovec)
 {
-       if (unlikely(!access_ok(!rw, buf, kiocb->ki_nbytes)))
+       size_t len = kiocb->ki_nbytes;
+
+       if (len > MAX_RW_COUNT)
+               len = MAX_RW_COUNT;
+
+       if (unlikely(!access_ok(!rw, buf, len)))
                return -EFAULT;
 
        iovec->iov_base = buf;
-       iovec->iov_len = kiocb->ki_nbytes;
+       iovec->iov_len = len;
        *nr_segs = 1;
        return 0;
 }