[PATCH v2] io_uring: preserve task restrictions across exec

[Kyumin Lee <fyonglkm@gmail.com>]

Per-task restrictions apply to all rings created by a task. Once installed,
they should not be dropped across exec.

For a task that has used io_uring, the exec cancellation path calls
__io_uring_free(). This frees both the task context and the per-task
restriction, so a ring created after exec is unrestricted.

Split task context cleanup into io_uring_free_tctx(), and use it from the
exec cancellation path. Keep __io_uring_free() for final task cleanup,
where both the context and restriction are released.

Fixes: ed82f35b926b ("io_uring: allow registration of per-task restrictions")
Cc: stable@vger.kernel.org # 7.1+
Signed-off-by: Kyumin Lee <fyonglkm@gmail.com>
---
Changes in v2:
- Resent as text/plain with no code changes.

 io_uring/cancel.c | 2 +-
 io_uring/tctx.c   | 7 ++++++-
 io_uring/tctx.h   | 1 +
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/io_uring/cancel.c b/io_uring/cancel.c
index 8c6fa6f367e4f..7d7820eab878b 100644
--- a/io_uring/cancel.c
+++ b/io_uring/cancel.c
@@ -660,6 +660,6 @@ __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd)
 		 */
 		atomic_dec(&tctx->in_cancel);
 		/* for exec all current's requests should be gone, kill tctx */
-		__io_uring_free(current);
+		io_uring_free_tctx(current);
 	}
 }
diff --git a/io_uring/tctx.c b/io_uring/tctx.c
index cc3bf2b3bdbc9..466b7300e208e 100644
--- a/io_uring/tctx.c
+++ b/io_uring/tctx.c
@@ -43,7 +43,7 @@ static struct io_wq *io_init_wq_offload(struct io_ring_ctx *ctx,
 	return io_wq_create(concurrency, &data);
 }
 
-void __io_uring_free(struct task_struct *tsk)
+void io_uring_free_tctx(struct task_struct *tsk)
 {
 	struct io_uring_task *tctx = tsk->io_uring;
 	struct io_tctx_node *node;
@@ -67,6 +67,11 @@ void __io_uring_free(struct task_struct *tsk)
 		kfree(tctx);
 		tsk->io_uring = NULL;
 	}
+}
+
+void __io_uring_free(struct task_struct *tsk)
+{
+	io_uring_free_tctx(tsk);
 	if (tsk->io_uring_restrict) {
 		io_put_bpf_filters(tsk->io_uring_restrict);
 		kfree(tsk->io_uring_restrict);
diff --git a/io_uring/tctx.h b/io_uring/tctx.h
index 2310d2a0c46d9..76ad1ad4594ef 100644
--- a/io_uring/tctx.h
+++ b/io_uring/tctx.h
@@ -12,6 +12,7 @@ void io_uring_del_tctx_node(unsigned long index);
 int __io_uring_add_tctx_node(struct io_ring_ctx *ctx);
 int __io_uring_add_tctx_node_from_submit(struct io_ring_ctx *ctx);
 void io_uring_clean_tctx(struct io_uring_task *tctx);
+void io_uring_free_tctx(struct task_struct *tsk);
 
 void io_uring_unreg_ringfd(void);
 int io_ringfd_register(struct io_ring_ctx *ctx, void __user *__arg,