pin iocb through aio.

aio_poll() is not the only case that needs file pinned; worse, while
aio_read()/aio_write() can live without pinning iocb itself, the
proof is rather brittle and can easily break on later changes.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 21 insertions, 16 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 38b741aef0bf..07083fc0a24b 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1022,6 +1022,9 @@ static bool get_reqs_available(struct kioctx *ctx)
 /* aio_get_req
  *      Allocate a slot for an aio request.
  * Returns NULL if no requests are free.
+ *
+ * The refcount is initialized to 2 - one for the async op completion,
+ * one for the synchronous code that does this.
  */
 static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
 {
@@ -1034,7 +1037,7 @@ static inline struct aio_kiocb *aio_get_req(struct kioctx *ctx)
         percpu_ref_get(&ctx->reqs);
         req->ki_ctx = ctx;
         INIT_LIST_HEAD(&req->ki_list);
-        refcount_set(&req->ki_refcnt, 0);
+        refcount_set(&req->ki_refcnt, 2);
         req->ki_eventfd = NULL;
         return req;
 }
@@ -1067,15 +1070,18 @@ out:
         return ret;
 }
 
+static inline void iocb_destroy(struct aio_kiocb *iocb)
+{
+        if (iocb->ki_filp)
+                fput(iocb->ki_filp);
+        percpu_ref_put(&iocb->ki_ctx->reqs);
+        kmem_cache_free(kiocb_cachep, iocb);
+}
+
 static inline void iocb_put(struct aio_kiocb *iocb)
 {
-        if (refcount_read(&iocb->ki_refcnt) == 0 ||
-            refcount_dec_and_test(&iocb->ki_refcnt)) {
-                if (iocb->ki_filp)
-                        fput(iocb->ki_filp);
-                percpu_ref_put(&iocb->ki_ctx->reqs);
-                kmem_cache_free(kiocb_cachep, iocb);
-        }
+        if (refcount_dec_and_test(&iocb->ki_refcnt))
+                iocb_destroy(iocb);
 }
 
 static void aio_fill_event(struct io_event *ev, struct aio_kiocb *iocb,
@@ -1749,9 +1755,6 @@ static ssize_t aio_poll(struct aio_kiocb *aiocb, const struct iocb *iocb)
         INIT_LIST_HEAD(&req->wait.entry);
         init_waitqueue_func_entry(&req->wait, aio_poll_wake);
 
-        /* one for removal from waitqueue, one for this function */
-        refcount_set(&aiocb->ki_refcnt, 2);
-
         mask = vfs_poll(req->file, &apt.pt) & req->events;
         if (unlikely(!req->head)) {
                 /* we did not manage to set up a waitqueue, done */
@@ -1782,7 +1785,6 @@ out:
 
         if (mask)
                 aio_poll_complete(aiocb, mask);
-        iocb_put(aiocb);
         return 0;
 }
 
@@ -1873,18 +1875,21 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
                 break;
         }
 
+        /* Done with the synchronous reference */
+        iocb_put(req);
+
         /*
          * If ret is 0, we'd either done aio_complete() ourselves or have
          * arranged for that to be done asynchronously.  Anything non-zero
          * means that we need to destroy req ourselves.
          */
-        if (ret)
-                goto out_put_req;
-        return 0;
+        if (!ret)
+                return 0;
+
 out_put_req:
         if (req->ki_eventfd)
                 eventfd_ctx_put(req->ki_eventfd);
-        iocb_put(req);
+        iocb_destroy(req);
 out_put_reqs_available:
         put_reqs_available(ctx, 1);
         return ret;