4.9-stable review patch. If anyone has any objections, please let me know.
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From: Lukas Czerner lczerner@redhat.com
commit ebacb81273599555a7a19f7754a1451206a5fc4f upstream.
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: 744742d692e3 ("fuse: Add reference counting for fuse_io_priv") Cc: stable@vger.kernel.org # v4.6 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/fuse/file.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
--- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2900,10 +2900,12 @@ fuse_direct_IO(struct kiocb *iocb, struc }
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);