The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 02a13674fa0e8dd326de8b9f4514b41b03d99003 Mon Sep 17 00:00:00 2001

From: Jens Axboe axboe@kernel.dk Date: Sat, 23 Jan 2021 15:49:31 -0700 Subject: [PATCH] io_uring: account io_uring internal files as REQ_F_INFLIGHT

We need to actively cancel anything that introduces a potential circular loop, where io_uring holds a reference to itself. If the file in question is an io_uring file, then add the request to the inflight list.

Cc: stable@vger.kernel.org # 5.9+ Signed-off-by: Jens Axboe axboe@kernel.dk

diff --git a/fs/io_uring.c b/fs/io_uring.c index 8a98afed50cd..c07913ec0cca 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1075,8 +1075,11 @@ static bool io_match_task(struct io_kiocb *head, return true;

io_for_each_link(req, head) { - if ((req->flags & REQ_F_WORK_INITIALIZED) && - (req->work.flags & IO_WQ_WORK_FILES) && + if (!(req->flags & REQ_F_WORK_INITIALIZED)) + continue; + if (req->file && req->file->f_op == &io_uring_fops) + return true; + if ((req->work.flags & IO_WQ_WORK_FILES) && req->work.identity->files == files) return true; } @@ -1505,11 +1508,14 @@ static bool io_grab_identity(struct io_kiocb *req) return false; atomic_inc(&id->files->count); get_nsproxy(id->nsproxy); - req->flags |= REQ_F_INFLIGHT;

- spin_lock_irq(&ctx->inflight_lock); - list_add(&req->inflight_entry, &ctx->inflight_list); - spin_unlock_irq(&ctx->inflight_lock); + if (!(req->flags & REQ_F_INFLIGHT)) { + req->flags |= REQ_F_INFLIGHT; + + spin_lock_irq(&ctx->inflight_lock); + list_add(&req->inflight_entry, &ctx->inflight_list); + spin_unlock_irq(&ctx->inflight_lock); + } req->work.flags |= IO_WQ_WORK_FILES; } if (!(req->work.flags & IO_WQ_WORK_MM) && @@ -6164,8 +6170,10 @@ static void io_req_drop_files(struct io_kiocb *req) struct io_uring_task *tctx = req->task->io_uring; unsigned long flags;

- put_files_struct(req->work.identity->files); - put_nsproxy(req->work.identity->nsproxy); + if (req->work.flags & IO_WQ_WORK_FILES) { + put_files_struct(req->work.identity->files); + put_nsproxy(req->work.identity->nsproxy); + } spin_lock_irqsave(&ctx->inflight_lock, flags); list_del(&req->inflight_entry); spin_unlock_irqrestore(&ctx->inflight_lock, flags); @@ -6450,6 +6458,15 @@ static struct file *io_file_get(struct io_submit_state *state, file = __io_file_get(state, fd); }

+ if (file && file->f_op == &io_uring_fops) { + io_req_init_async(req); + req->flags |= REQ_F_INFLIGHT; + + spin_lock_irq(&ctx->inflight_lock); + list_add(&req->inflight_entry, &ctx->inflight_list); + spin_unlock_irq(&ctx->inflight_lock); + } + return file; }

@@ -8860,8 +8877,7 @@ static void io_uring_cancel_files(struct io_ring_ctx *ctx,

spin_lock_irq(&ctx->inflight_lock); list_for_each_entry(req, &ctx->inflight_list, inflight_entry) { - if (req->task != task || - req->work.identity->files != files) + if (!io_match_task(req, task, files)) continue; found = true; break;