io_uring: fix races with buffer table unregister

[ Upstream commit d11d31f ] Fixed buffer table quiesce might unlock ->uring_lock, potentially letting new requests to be submitted, don't allow those requests to use the table as they will race with unregistration. Reported-and-tested-by: van fantasy <[email protected]> Fixes: bd54b6f ("io_uring: implement fixed buffers registration similar to fixed files") Signed-off-by: Pavel Begunkov <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
ADVANTECH-Corp · Jun 22, 2022 · 91f5a60 · 91f5a60
1 parent b1e7cad
commit 91f5a60
Showing 1 changed file with 7 additions and 0 deletions.
diff --git a/fs/io_uring.c b/fs/io_uring.c
@@ -8905,12 +8905,19 @@ static void __io_sqe_buffers_unregister(struct io_ring_ctx *ctx)
 
 static int io_sqe_buffers_unregister(struct io_ring_ctx *ctx)
 {
+	unsigned nr = ctx->nr_user_bufs;
 	int ret;
 
 	if (!ctx->buf_data)
 		return -ENXIO;
 
+	/*
+	 * Quiesce may unlock ->uring_lock, and while it's not held
+	 * prevent new requests using the table.
+	 */
+	ctx->nr_user_bufs = 0;
 	ret = io_rsrc_ref_quiesce(ctx->buf_data, ctx);
+	ctx->nr_user_bufs = nr;
 	if (!ret)
 		__io_sqe_buffers_unregister(ctx);
 	return ret;