[PATCH 1/1] io_uring: sanitise ring params earlier

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

Do all struct io_uring_params validation early on before allocating the
context. That makes initialisation easier, especially by having fewer
places where we need to care about partial de-initialisation.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 io_uring/io_uring.c | 77 ++++++++++++++++++++++++++-------------------
 1 file changed, 44 insertions(+), 33 deletions(-)

diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index fad178325cb2b..1824f5da168fd 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -3535,6 +3535,44 @@ static struct file *io_uring_get_file(struct io_ring_ctx *ctx)
 					 O_RDWR | O_CLOEXEC, NULL);
 }
 
+static int io_uring_sanitise_params(struct io_uring_params *p)
+{
+	unsigned flags = p->flags;
+
+	/* There is no way to mmap rings without a real fd */
+	if ((flags & IORING_SETUP_REGISTERED_FD_ONLY) &&
+	    !(flags & IORING_SETUP_NO_MMAP))
+		return -EINVAL;
+
+	if (flags & IORING_SETUP_SQPOLL) {
+		/* IPI related flags don't make sense with SQPOLL */
+		if (flags & (IORING_SETUP_COOP_TASKRUN |
+			     IORING_SETUP_TASKRUN_FLAG |
+			     IORING_SETUP_DEFER_TASKRUN))
+			return -EINVAL;
+	}
+
+	if (flags & IORING_SETUP_TASKRUN_FLAG) {
+		if (!(flags & (IORING_SETUP_COOP_TASKRUN |
+			       IORING_SETUP_DEFER_TASKRUN)))
+			return -EINVAL;
+	}
+
+	/* HYBRID_IOPOLL only valid with IOPOLL */
+	if ((flags & IORING_SETUP_HYBRID_IOPOLL) && !(flags & IORING_SETUP_IOPOLL))
+		return -EINVAL;
+
+	/*
+	 * For DEFER_TASKRUN we require the completion task to be the same as
+	 * the submission task. This implies that there is only one submitter.
+	 */
+	if ((flags & IORING_SETUP_DEFER_TASKRUN) &&
+	    !(flags & IORING_SETUP_SINGLE_ISSUER))
+		return -EINVAL;
+
+	return 0;
+}
+
 int io_uring_fill_params(unsigned entries, struct io_uring_params *p)
 {
 	if (!entries)
@@ -3545,10 +3583,6 @@ int io_uring_fill_params(unsigned entries, struct io_uring_params *p)
 		entries = IORING_MAX_ENTRIES;
 	}
 
-	if ((p->flags & IORING_SETUP_REGISTERED_FD_ONLY)
-	    && !(p->flags & IORING_SETUP_NO_MMAP))
-		return -EINVAL;
-
 	/*
 	 * Use twice as many entries for the CQ ring. It's possible for the
 	 * application to drive a higher depth than the size of the SQ ring,
@@ -3610,6 +3644,10 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
 	struct file *file;
 	int ret;
 
+	ret = io_uring_sanitise_params(p);
+	if (ret)
+		return ret;
+
 	ret = io_uring_fill_params(entries, p);
 	if (unlikely(ret))
 		return ret;
@@ -3657,37 +3695,10 @@ static __cold int io_uring_create(unsigned entries, struct io_uring_params *p,
 	 * For SQPOLL, we just need a wakeup, always. For !SQPOLL, if
 	 * COOP_TASKRUN is set, then IPIs are never needed by the app.
 	 */
-	ret = -EINVAL;
-	if (ctx->flags & IORING_SETUP_SQPOLL) {
-		/* IPI related flags don't make sense with SQPOLL */
-		if (ctx->flags & (IORING_SETUP_COOP_TASKRUN |
-				  IORING_SETUP_TASKRUN_FLAG |
-				  IORING_SETUP_DEFER_TASKRUN))
-			goto err;
+	if (ctx->flags & (IORING_SETUP_SQPOLL|IORING_SETUP_COOP_TASKRUN))
 		ctx->notify_method = TWA_SIGNAL_NO_IPI;
-	} else if (ctx->flags & IORING_SETUP_COOP_TASKRUN) {
-		ctx->notify_method = TWA_SIGNAL_NO_IPI;
-	} else {
-		if (ctx->flags & IORING_SETUP_TASKRUN_FLAG &&
-		    !(ctx->flags & IORING_SETUP_DEFER_TASKRUN))
-			goto err;
+	else
 		ctx->notify_method = TWA_SIGNAL;
-	}
-
-	/* HYBRID_IOPOLL only valid with IOPOLL */
-	if ((ctx->flags & (IORING_SETUP_IOPOLL|IORING_SETUP_HYBRID_IOPOLL)) ==
-			IORING_SETUP_HYBRID_IOPOLL)
-		goto err;
-
-	/*
-	 * For DEFER_TASKRUN we require the completion task to be the same as the
-	 * submission task. This implies that there is only one submitter, so enforce
-	 * that.
-	 */
-	if (ctx->flags & IORING_SETUP_DEFER_TASKRUN &&
-	    !(ctx->flags & IORING_SETUP_SINGLE_ISSUER)) {
-		goto err;
-	}
 
 	/*
 	 * This is just grabbed for accounting purposes. When a process exits,
-- 
2.47.1