[PATCH 5.10 20/63] io_uring: fix io_sqe_files_unregister() hangs

[Greg Kroah-Hartman]

From: Pavel Begunkov <asml.sile...@gmail.com>

commit 1ffc54220c444774b7f09e6d2121e732f8e19b94 upstream.

io_sqe_files_unregister() uninterruptibly waits for enqueued ref nodes,
however requests keeping them may never complete, e.g. because of some
userspace dependency. Make sure it's interruptible otherwise it would
hang forever.

Cc: sta...@vger.kernel.org # 5.6+
Signed-off-by: Pavel Begunkov <asml.sile...@gmail.com>
Signed-off-by: Jens Axboe <ax...@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 fs/io_uring.c |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -941,6 +941,10 @@ enum io_mem_account {
        ACCT_PINNED,
 };
 
+static void destroy_fixed_file_ref_node(struct fixed_file_ref_node *ref_node);
+static struct fixed_file_ref_node *alloc_fixed_file_ref_node(
+                       struct io_ring_ctx *ctx);
+
 static void __io_complete_rw(struct io_kiocb *req, long res, long res2,
                             struct io_comp_state *cs);
 static void io_cqring_fill_event(struct io_kiocb *req, long res);
@@ -7004,11 +7008,15 @@ static void io_sqe_files_set_node(struct
 static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
 {
        struct fixed_file_data *data = ctx->file_data;
-       struct fixed_file_ref_node *ref_node = NULL;
+       struct fixed_file_ref_node *backup_node, *ref_node = NULL;
        unsigned nr_tables, i;
+       int ret;
 
        if (!data)
                return -ENXIO;
+       backup_node = alloc_fixed_file_ref_node(ctx);
+       if (!backup_node)
+               return -ENOMEM;
 
        spin_lock_bh(&data->lock);
        ref_node = data->node;
@@ -7020,7 +7028,18 @@ static int io_sqe_files_unregister(struc
 
        /* wait for all refs nodes to complete */
        flush_delayed_work(&ctx->file_put_work);
-       wait_for_completion(&data->done);
+       do {
+               ret = wait_for_completion_interruptible(&data->done);
+               if (!ret)
+                       break;
+               ret = io_run_task_work_sig();
+               if (ret < 0) {
+                       percpu_ref_resurrect(&data->refs);
+                       reinit_completion(&data->done);
+                       io_sqe_files_set_node(data, backup_node);
+                       return ret;
+               }
+       } while (1);
 
        __io_sqe_files_unregister(ctx);
        nr_tables = DIV_ROUND_UP(ctx->nr_user_files, IORING_MAX_FILES_TABLE);
@@ -7031,6 +7050,7 @@ static int io_sqe_files_unregister(struc
        kfree(data);
        ctx->file_data = NULL;
        ctx->nr_user_files = 0;
+       destroy_fixed_file_ref_node(backup_node);
        return 0;
 }