From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E7D75FC06; Mon, 11 Dec 2023 18:33:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VcY0XWHc" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6924FC433CB; Mon, 11 Dec 2023 18:33:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1702319629; bh=pNhvH8vJMgJulFZJZ67BbfdzSeXbNRzdv14WaYFt6LE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VcY0XWHc76XSY8LEGA245aY7AG+uWRE40NOwbl/O6uG+hXnbLtW49TdmpZpn+nKxH bXgxW2U+cJsW+SDa0e3g6dP7HiDbyiBdJQ4rwcWlW2y58/gR2boP3sLwld1BYiErzC yjtWpPYJmO9sMSP/KxsWw80mZGFMR5yN7zmCWbvQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jann Horn , Pavel Begunkov , Jens Axboe Subject: [PATCH 6.6 136/244] io_uring: fix mutex_unlock with unreferenced ctx Date: Mon, 11 Dec 2023 19:20:29 +0100 Message-ID: <20231211182051.884896098@linuxfoundation.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20231211182045.784881756@linuxfoundation.org> References: <20231211182045.784881756@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Pavel Begunkov commit f7b32e785042d2357c5abc23ca6db1b92c91a070 upstream. Callers of mutex_unlock() have to make sure that the mutex stays alive for the whole duration of the function call. For io_uring that means that the following pattern is not valid unless we ensure that the context outlives the mutex_unlock() call. mutex_lock(&ctx->uring_lock); req_put(req); // typically via io_req_task_submit() mutex_unlock(&ctx->uring_lock); Most contexts are fine: io-wq pins requests, syscalls hold the file, task works are taking ctx references and so on. However, the task work fallback path doesn't follow the rule. Cc: Fixes: 04fc6c802d ("io_uring: save ctx put/get for task_work submit") Reported-by: Jann Horn Signed-off-by: Pavel Begunkov Link: https://lore.kernel.org/io-uring/CAG48ez3xSoYb+45f1RLtktROJrpiDQ1otNvdR+YLQf7m+Krj5Q@mail.gmail.com/ Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- io_uring/io_uring.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -269,6 +269,7 @@ static __cold void io_fallback_req_func( struct io_kiocb *req, *tmp; struct io_tw_state ts = { .locked = true, }; + percpu_ref_get(&ctx->refs); mutex_lock(&ctx->uring_lock); llist_for_each_entry_safe(req, tmp, node, io_task_work.node) req->io_task_work.func(req, &ts); @@ -276,6 +277,7 @@ static __cold void io_fallback_req_func( return; io_submit_flush_completions(ctx); mutex_unlock(&ctx->uring_lock); + percpu_ref_put(&ctx->refs); } static int io_alloc_hash_table(struct io_hash_table *table, unsigned bits) @@ -3138,12 +3140,7 @@ static __cold void io_ring_exit_work(str init_completion(&exit.completion); init_task_work(&exit.task_work, io_tctx_exit_cb); exit.ctx = ctx; - /* - * Some may use context even when all refs and requests have been put, - * and they are free to do so while still holding uring_lock or - * completion_lock, see io_req_task_submit(). Apart from other work, - * this lock/unlock section also waits them to finish. - */ + mutex_lock(&ctx->uring_lock); while (!list_empty(&ctx->tctx_list)) { WARN_ON_ONCE(time_after(jiffies, timeout));