[PATCH 2/4] io_uring: fix io_sqe_files_unregister() hangs

Pavel Begunkov
2020-12-30T21:38:49Z

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: stable@vger.kernel.org # 5.6+
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
fs/io_uring.c | 24 ++++++++++++++++++++++--
1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6372aba8d0c2..ca46f314640b 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -992,6 +992,10 @@ 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);
@@ -7244,11 +7248,15 @@ static void io_sqe_files_set_node(struct fixed_file_data *file_data,
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;
@@ -7260,7 +7268,18 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)

/* 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);
@@ -7271,6 +7290,7 @@ static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
kfree(data);
ctx->file_data = NULL;
ctx->nr_user_files = 0;
+ destroy_fixed_file_ref_node(backup_node);
return 0;
}

--
2.24.0