[PATCH 1/8] aio: make sure file is pinned

[Al Viro <viro@ZenIV.linux.org.uk>]

From: Al Viro <viro@zeniv.linux.org.uk>

"aio: remove the extra get_file/fput pair in io_submit_one" was
too optimistic - not dereferencing file pointer after e.g.
->write_iter() returns is not enough; that reference might've been
the only thing that kept alive objects that are referenced
*before* the method returns.  Such as inode, for example...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/aio.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/aio.c b/fs/aio.c
index 3d9669d011b9..ea30b78187ed 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1790,6 +1790,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 			   struct iocb __user *user_iocb, bool compat)
 {
 	struct aio_kiocb *req;
+	struct file *file;
 	ssize_t ret;
 
 	/* enforce forwards compatibility on users */
@@ -1844,6 +1845,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 
 	req->ki_user_iocb = user_iocb;
 	req->ki_user_data = iocb->aio_data;
+	file = get_file(req->ki_filp);	/* req can die too early */
 
 	switch (iocb->aio_lio_opcode) {
 	case IOCB_CMD_PREAD:
@@ -1872,6 +1874,7 @@ static int __io_submit_one(struct kioctx *ctx, const struct iocb *iocb,
 		ret = -EINVAL;
 		break;
 	}
+	fput(file);
 
 	/*
 	 * If ret is 0, we'd either done aio_complete() ourselves or have
-- 
2.11.0