Commit ebacb812 authored Nov 09, 2018 by Lukas Czerner Committed by Miklos Szeredi Nov 09, 2018

fuse: fix use-after-free in fuse_direct_IO()



In async IO blocking case the additional reference to the io is taken for
it to survive fuse_aio_complete(). In non blocking case this additional
reference is not needed, however we still reference io to figure out
whether to wait for completion or not. This is wrong and will lead to
use-after-free. Fix it by storing blocking information in separate
variable.

This was spotted by KASAN when running generic/208 fstest.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 744742d6 ("fuse: Add reference counting for fuse_io_priv")
Cc: <stable@vger.kernel.org> # v4.6

parent 2d84a2d1

fs/fuse/file.c

+3 −1

Original line number	Diff line number	Diff line
		@@ -2924,10 +2924,12 @@ fuse_direct_IO(struct kiocb iocb, struct iov_iter iter)
		}

		if (io->async) {
		bool blocking = io->blocking;

		fuse_aio_complete(io, ret < 0 ? ret : 0, -1);

		/* we have a non-extending, async request, so return */
		if (!io->blocking)
		if (!blocking)
		return -EIOCBQUEUED;

		wait_for_completion(&wait);

Admin message