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authorJens Axboe <axboe@kernel.dk>2020-06-17 02:42:49 +0200
committerJens Axboe <axboe@kernel.dk>2020-06-17 20:49:16 +0200
commit9d8426a09195e2dcf2aa249de2aaadd792d491c7 (patch)
tree869fea84308ffa827fcd92a85d6fbe55686213a9 /fs
parentio_uring: add memory barrier to synchronize io_kiocb's result and iopoll_comp... (diff)
downloadlinux-9d8426a09195e2dcf2aa249de2aaadd792d491c7.tar.xz
linux-9d8426a09195e2dcf2aa249de2aaadd792d491c7.zip
io_uring: acquire 'mm' for task_work for SQPOLL
If we're unlucky with timing, we could be running task_work after having dropped the memory context in the sq thread. Since dropping the context requires a runnable task state, we cannot reliably drop it as part of our check-for-work loop in io_sq_thread(). Instead, abstract out the mm acquire for the sq thread into a helper, and call it from the async task work handler. Cc: stable@vger.kernel.org # v5.7 Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'fs')
-rw-r--r--fs/io_uring.c44
1 files changed, 29 insertions, 15 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 9d2ae9aa8b45..98c83fbf4f88 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4256,6 +4256,28 @@ static void io_async_queue_proc(struct file *file, struct wait_queue_head *head,
__io_queue_proc(&pt->req->apoll->poll, pt, head);
}
+static void io_sq_thread_drop_mm(struct io_ring_ctx *ctx)
+{
+ struct mm_struct *mm = current->mm;
+
+ if (mm) {
+ kthread_unuse_mm(mm);
+ mmput(mm);
+ }
+}
+
+static int io_sq_thread_acquire_mm(struct io_ring_ctx *ctx,
+ struct io_kiocb *req)
+{
+ if (io_op_defs[req->opcode].needs_mm && !current->mm) {
+ if (unlikely(!mmget_not_zero(ctx->sqo_mm)))
+ return -EFAULT;
+ kthread_use_mm(ctx->sqo_mm);
+ }
+
+ return 0;
+}
+
static void io_async_task_func(struct callback_head *cb)
{
struct io_kiocb *req = container_of(cb, struct io_kiocb, task_work);
@@ -4290,11 +4312,16 @@ static void io_async_task_func(struct callback_head *cb)
if (!canceled) {
__set_current_state(TASK_RUNNING);
+ if (io_sq_thread_acquire_mm(ctx, req)) {
+ io_cqring_add_event(req, -EFAULT);
+ goto end_req;
+ }
mutex_lock(&ctx->uring_lock);
__io_queue_sqe(req, NULL);
mutex_unlock(&ctx->uring_lock);
} else {
io_cqring_ev_posted(ctx);
+end_req:
req_set_fail_links(req);
io_double_put_req(req);
}
@@ -5841,11 +5868,8 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
if (unlikely(req->opcode >= IORING_OP_LAST))
return -EINVAL;
- if (io_op_defs[req->opcode].needs_mm && !current->mm) {
- if (unlikely(!mmget_not_zero(ctx->sqo_mm)))
- return -EFAULT;
- kthread_use_mm(ctx->sqo_mm);
- }
+ if (unlikely(io_sq_thread_acquire_mm(ctx, req)))
+ return -EFAULT;
sqe_flags = READ_ONCE(sqe->flags);
/* enforce forwards compatibility on users */
@@ -5954,16 +5978,6 @@ fail_req:
return submitted;
}
-static inline void io_sq_thread_drop_mm(struct io_ring_ctx *ctx)
-{
- struct mm_struct *mm = current->mm;
-
- if (mm) {
- kthread_unuse_mm(mm);
- mmput(mm);
- }
-}
-
static int io_sq_thread(void *data)
{
struct io_ring_ctx *ctx = data;