io_steal_work() can't be sure that @nxt have req->work
properly set, so we can't pass it to io-wq as is.
A dirty quick fix -- drag it through io_req_task_queue(),
and always return NULL from io_steal_work().
e.g.
[ 50.770161] BUG: kernel NULL pointer dereference, address: 00000000
[ 50.770164] #PF: supervisor write access in kernel mode
[ 50.770164] #PF: error_code(0x0002) - not-present page
[ 50.770168] CPU: 1 PID: 1448 Comm: io_wqe_worker-0 Tainted: G
I 5.8.0-rc2-00035-g2237d76530eb-dirty #494
[ 50.770172] RIP: 0010:override_creds+0x19/0x30
...
[ 50.770183] io_worker_handle_work+0x25c/0x430
[ 50.770185] io_wqe_worker+0x2a0/0x350
[ 50.770190] kthread+0x136/0x180
[ 50.770194] ret_from_fork+0x22/0x30
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
fs/io_uring.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index e10aeae8cc52..b577d6f50cbc 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1791,7 +1791,7 @@ static void io_put_req(struct io_kiocb *req)
static struct io_wq_work *io_steal_work(struct io_kiocb *req)
{
- struct io_kiocb *link, *nxt = NULL;
+ struct io_kiocb *nxt = NULL;
/*
* A ref is owned by io-wq in which context we're. So, if that's the
@@ -1808,10 +1808,15 @@ static struct io_wq_work *io_steal_work(struct io_kiocb *req)
if ((nxt->flags & REQ_F_ISREG) && io_op_defs[nxt->opcode].hash_reg_file)
io_wq_hash_work(&nxt->work, file_inode(nxt->file));
- link = io_prep_linked_timeout(nxt);
- if (link)
- nxt->flags |= REQ_F_QUEUE_TIMEOUT;
- return &nxt->work;
+ io_req_task_queue(nxt);
+ /*
+ * If we're going to return actual work, here should be timeout prep:
+ *
+ * link = io_prep_linked_timeout(nxt);
+ * if (link)
+ * nxt->flags |= REQ_F_QUEUE_TIMEOUT;
+ */
+ return NULL;
}
/*
--
2.24.0
