ceph: do not access the kiocb after aio requests

In aio case, if the completion comes very fast just before the
ceph_read_iter() returns to fs/aio.c, the kiocb will be freed in
the completion callback, then if ceph_read_iter() access again
we will potentially hit the use-after-free bug.

[ jlayton: initialize direct_lock early, and use it everywhere ]

URL: https://tracker.ceph.com/issues/45649
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 160644d..d51c3f2 100644 (file)
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1538,6 +1538,7 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to)
        struct inode *inode = file_inode(filp);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct page *pinned_page = NULL;
+       bool direct_lock = iocb->ki_flags & IOCB_DIRECT;
        ssize_t ret;
        int want, got = 0;
        int retry_op = 0, read = 0;
@@ -1546,7 +1547,7 @@ again:
        dout("aio_read %p %llx.%llx %llu~%u trying to get caps on %p\n",
             inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len, inode);
 
-       if (iocb->ki_flags & IOCB_DIRECT)
+       if (direct_lock)
                ceph_start_io_direct(inode);
        else
                ceph_start_io_read(inode);
@@ -1603,7 +1604,7 @@ again:
        }
        ceph_put_cap_refs(ci, got);
 
-       if (iocb->ki_flags & IOCB_DIRECT)
+       if (direct_lock)
                ceph_end_io_direct(inode);
        else
                ceph_end_io_read(inode);