io_uring: fix double prep iovec leak

Requests may be prepared multiple times with ->io allocated (i.e. async
prepared). Preparation functions don'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 check, whether they already allocated resources, which
is true IFF REQ_F_NEED_CLEANUP is set.

Cc: stable@vger.kernel.org # 5.5
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 759301b..0977017 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2205,7 +2205,8 @@ 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;
@@ -2293,7 +2294,8 @@ 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;
@@ -2993,6 +2995,9 @@ 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,
@@ -3143,6 +3148,9 @@ 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,