[PATCH] fuse: Fix use-after-free in fuse_dev_do_write()

[Kirill Tkhai]

After we found req in request_find() and released the lock,
everything may happen with the req in parallel.

Keep it alive till we finish touch its memory.

Signed-off-by: Kirill Tkhai <ktk...@virtuozzo.com>
---
 fs/fuse/dev.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
index 675caed3e655..c2af8042f176 100644
--- a/fs/fuse/dev.c
+++ b/fs/fuse/dev.c
@@ -1877,16 +1877,20 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud,
 
        /* Is it an interrupt reply? */
        if (req->intr_unique == oh.unique) {
+               __fuse_get_request(req);
                spin_unlock(&fpq->lock);
 
                err = -EINVAL;
-               if (nbytes != sizeof(struct fuse_out_header))
+               if (nbytes != sizeof(struct fuse_out_header)) {
+                       fuse_put_request(fc, req);
                        goto err_finish;
+               }
 
                if (oh.error == -ENOSYS)
                        fc->no_interrupt = 1;
                else if (oh.error == -EAGAIN)
                        queue_interrupt(&fc->iq, req);
+               fuse_put_request(fc, req);
 
                fuse_copy_finish(cs);
                return nbytes;