We can have a task exit if it's not the owner of the ring. Be safe and
grab an actual reference to it, to avoid a potential use-after-free.
Reported-by: Dan Melnic <dmm@xxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
fs/io_uring.c | 19 +++++++------------
1 file changed, 7 insertions(+), 12 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 8ad4a151994d..b343525a4d2e 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -615,10 +615,8 @@ struct io_kiocb {
struct list_head list;
unsigned int flags;
refcount_t refs;
- union {
- struct task_struct *task;
- unsigned long fsize;
- };
+ struct task_struct *task;
+ unsigned long fsize;
u64 user_data;
u32 result;
u32 sequence;
@@ -1336,6 +1334,7 @@ static struct io_kiocb *io_get_req(struct io_ring_ctx *ctx,
req->flags = 0;
/* one is dropped after submission, the other at completion */
refcount_set(&req->refs, 2);
+ req->task = NULL;
req->result = 0;
INIT_IO_WORK(&req->work, io_wq_submit_work);
return req;
@@ -1372,6 +1371,8 @@ static void __io_req_aux_free(struct io_kiocb *req)
kfree(req->io);
if (req->file)
io_put_file(req, req->file, (req->flags & REQ_F_FIXED_FILE));
+ if (req->task)
+ put_task_struct(req->task);
io_req_work_drop_env(req);
}
@@ -4256,10 +4257,7 @@ static bool io_arm_poll_handler(struct io_kiocb *req)
req->flags |= REQ_F_POLLED;
memcpy(&apoll->work, &req->work, sizeof(req->work));
- /*
- * Don't need a reference here, as we're adding it to the task
- * task_works list. If the task exits, the list is pruned.
- */
+ get_task_struct(current);
req->task = current;
req->apoll = apoll;
INIT_HLIST_NODE(&req->hash_node);
@@ -4482,10 +4480,7 @@ static int io_poll_add_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe
events = READ_ONCE(sqe->poll_events);
poll->events = demangle_poll(events) | EPOLLERR | EPOLLHUP;
- /*
- * Don't need a reference here, as we're adding it to the task
- * task_works list. If the task exits, the list is pruned.
- */
+ get_task_struct(current);
req->task = current;
return 0;
}
--
2.26.0
