From f0f8d236e56e272cabed04add90a64946fde94b9 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Sun, 28 Jun 2020 20:47:09 +0800 Subject: [PATCH 1580/2944] io_uring: acquire 'mm' for task_work for SQPOLL to #28736503 commit 9d8426a09195e2dcf2aa249de2aaadd792d491c7 upstream 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 Signed-off-by: Xiaoguang Wang Acked-by: Joseph Qi --- fs/io_uring.c | 44 +++++++++++++++++++++++++++++--------------- 1 file changed, 29 insertions(+), 15 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index c1e9f3f..b554323 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4246,6 +4246,28 @@ 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) { + 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; + 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); @@ -4280,11 +4302,16 @@ 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); } @@ -5831,11 +5858,8 @@ 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; - 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 */ @@ -5944,16 +5968,6 @@ static int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr, return submitted; } -static inline void io_sq_thread_drop_mm(struct io_ring_ctx *ctx) -{ - struct mm_struct *mm = current->mm; - - if (mm) { - unuse_mm(mm); - mmput(mm); - } -} - static int io_sq_thread(void *data) { struct io_ring_ctx *ctx = data; -- 1.8.3.1