ext4: fix possible use-after-free with AIO

commit 091e26dfc156aeb3b73bc5c5f277e433ad39331c upstream.

Running AIO is pinning inode in memory using file reference. Once AIO
is completed using aio_complete(), file reference is put and inode can
be freed from memory. So we have to be sure that calling aio_complete()
is the last thing we do with the inode.

Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 770eeb3aecf3a770f22bb255b22e408deca27b39..4b2bb7546fc0be5cc556909bce8f75267bf04e8b 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2795,9 +2795,9 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
        if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
                ext4_free_io_end(io_end);
 out:
+               inode_dio_done(inode);
                if (is_async)
                        aio_complete(iocb, ret, 0);
-               inode_dio_done(inode);
                return;
        }
 

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 24feb1ced3fda1e52d84826aeea2d5a6dbb90548..54f566d971767b764fb9a5d6cd450f97728f9082 100644 (file)
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -108,14 +108,13 @@ int ext4_end_io_nolock(ext4_io_end_t *io)
                         inode->i_ino, offset, size, ret);
        }
 
-       if (io->iocb)
-               aio_complete(io->iocb, io->result, 0);
-
-       if (io->flag & EXT4_IO_END_DIRECT)
-               inode_dio_done(inode);
        /* Wake up anyone waiting on unwritten extent conversion */
        if (atomic_dec_and_test(&EXT4_I(inode)->i_aiodio_unwritten))
                wake_up_all(ext4_ioend_wq(io->inode));
+       if (io->flag & EXT4_IO_END_DIRECT)
+               inode_dio_done(inode);
+       if (io->iocb)
+               aio_complete(io->iocb, io->result, 0);
        return ret;
 }