[PATCH 1/2] io_uring: fix double prep iovec leak

[Pavel Begunkov <asml.silence@gmail.com>]

Requests may be prepared multiple times with ->io allocated (i.e. async
prepared). Preparation functions doesn't handle it and forget about
previously allocated resources. This may happen in case of:
- spurious defer_check
- non-head (i.e. async prepared) request executed in sync (via nxt).

Make the handlers to check, whether they already allocated resources,
what is true IFF REQ_F_NEED_CLEANUP is set.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io_uring.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1698b4950366..f5aa2fdccf7a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2187,7 +2187,8 @@ static int io_read_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	if (unlikely(!(req->file->f_mode & FMODE_READ)))
 		return -EBADF;
 
-	if (!req->io)
+	/* either don't need iovec imported or already have it */
+	if (!req->io || req->flags & REQ_F_NEED_CLEANUP)
 		return 0;
 
 	io = req->io;
@@ -2275,7 +2276,8 @@ static int io_write_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe,
 	if (unlikely(!(req->file->f_mode & FMODE_WRITE)))
 		return -EBADF;
 
-	if (!req->io)
+	/* either don't need iovec imported or already have it */
+	if (!req->io || req->flags & REQ_F_NEED_CLEANUP)
 		return 0;
 
 	io = req->io;
@@ -2981,6 +2983,9 @@ static int io_sendmsg_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
 
 	if (!io || req->opcode == IORING_OP_SEND)
 		return 0;
+	/* iovec is already imported */
+	if (req->flags & REQ_F_NEED_CLEANUP)
+		return 0;
 
 	io->msg.iov = io->msg.fast_iov;
 	ret = sendmsg_copy_msghdr(&io->msg.msg, sr->msg, sr->msg_flags,
@@ -3131,6 +3136,9 @@ static int io_recvmsg_prep(struct io_kiocb *req,
 
 	if (!io || req->opcode == IORING_OP_RECV)
 		return 0;
+	/* iovec is already imported */
+	if (req->flags & REQ_F_NEED_CLEANUP)
+		return 0;
 
 	io->msg.iov = io->msg.fast_iov;
 	ret = recvmsg_copy_msghdr(&io->msg.msg, sr->msg, sr->msg_flags,
-- 
2.24.0