From patchwork Tue Nov 22 18:40:15 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lin Ma X-Patchwork-Id: 24502 Return-Path: Delivered-To: ouuuleilei@gmail.com Received: by 2002:adf:f944:0:0:0:0:0 with SMTP id q4csp2382053wrr; Tue, 22 Nov 2022 10:47:32 -0800 (PST) X-Google-Smtp-Source: AA0mqf4p3HwRYNTvFlgTqK/ImfXXzodwosamr/CiUWvuT9Cwk0jI1JvzGHVCr1WxWMxEsSbMOZBz X-Received: by 2002:aa7:cc8d:0:b0:461:15f0:a574 with SMTP id p13-20020aa7cc8d000000b0046115f0a574mr22422971edt.187.1669142852037; Tue, 22 Nov 2022 10:47:32 -0800 (PST) ARC-Seal: i=1; a=rsa-sha256; t=1669142852; cv=none; d=google.com; s=arc-20160816; b=WkN8xfCqp5TJmrBcnlF3a9GOdNCxE8uk/AEFJEWGCTAkTY282fT40xMarT+N2hDLFK ELmXGeak93hXdETSd2kVl2GRaIyuuMj0Wv/Bm19rawNzK+X7523l40cSQlnXpfDPzdk7 ESTqpbTWLYxAaCCtTt7h3enZ7oLrzwIzMRZE2pkM1GFipY1bwxq+zBIrfxN/kxC1SKkF NK/OEXiOkEpETFohzr0Fr28ux8m0sdC+0plM5WucNe5V4T8PeRTZ/bN7i3Xw9KAeiBvE Cbxlv59Rc/027IIkG6Vc/im1JKmZdrbKgP26RfbOi06wvQVJe4a1gOVhi+jhfll5YrxJ +QpA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:message-id:mime-version :content-transfer-encoding:subject:to:from:date; bh=cmE5sA4j2PJ1YvpDrQwqh21gEX4ATPnsTmsP0A/FGII=; b=EL/+OAQF/FgxYjYMGKHq+mpRUEkw0IcgKh0KLKbPOeCIVdJ+SjUmmFrDC/SEv9Mv9H lhL11R+hqhKHvJlhvRaG/VWaLuqX2kz7SYpHSO52znD4u2zphLJ2xORmaJPSRN7ykL0N 7kCi/SxM3aLRaDw4U/dqT6Ggm0PzCGb/JlK2TjzylsFqE3gUgBRUsDO+uiE26e6+erMM Pddn0TO2NFgOsODId8kj42B8j4RJKjvM7WGdORPrd+g1K/oEenuf5DF+QSKpY7Xt+l+w abw/+B55GCqSA2Z5sKYPmAyhs4iRb/smRi0jm02PX6XHtaCoYIZw3ckyeWuEBFdBZOJ8 jv0g== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: from out1.vger.email (out1.vger.email. [2620:137:e000::1:20]) by mx.google.com with ESMTP id gt42-20020a1709072daa00b007882936243fsi2754464ejc.772.2022.11.22.10.47.06; Tue, 22 Nov 2022 10:47:32 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233081AbiKVSk0 (ORCPT + 99 others); Tue, 22 Nov 2022 13:40:26 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45128 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234415AbiKVSkX (ORCPT ); Tue, 22 Nov 2022 13:40:23 -0500 Received: from zju.edu.cn (spam.zju.edu.cn [61.164.42.155]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id AD8B17FF01; Tue, 22 Nov 2022 10:40:18 -0800 (PST) Received: by ajax-webmail-mail-app4 (Coremail) ; Wed, 23 Nov 2022 02:40:15 +0800 (GMT+08:00) X-Originating-IP: [10.192.27.165] Date: Wed, 23 Nov 2022 02:40:15 +0800 (GMT+08:00) X-CM-HeaderCharset: UTF-8 From: "Lin Ma" To: axboe@kernel.dk, asml.silence@gmail.com, io-uring@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2] io_uring/filetable: fix file reference underflow X-Priority: 3 X-Mailer: Coremail Webmail Server Version XT5.0.13 build 20210104(ab8c30b6) Copyright (c) 2002-2022 www.mailtech.cn zju.edu.cn MIME-Version: 1.0 Message-ID: X-Coremail-Locale: en_US X-CM-TRANSID: cS_KCgA3OMyQF31jqjpFCA--.49693W X-CM-SenderInfo: qtrwiiyqvtljo62m3hxhgxhubq/1tbiAwQRElNG3I7oMgANsU X-Coremail-Antispam: 1Ur529EdanIXcx71UUUUU7IcSsGvfJ3iIAIbVAYjsxI4VW3Jw CS07vEb4IE77IF4wCS07vE1I0E4x80FVAKz4kxMIAIbVAFxVCaYxvI4VCIwcAKzIAtYxBI daVFxhVjvjDU= X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_PASS, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1750223135048557882?= X-GMAIL-MSGID: =?utf-8?q?1750223135048557882?= There is an interesting reference bug when -ENOMEM occurs in calling of io_install_fixed_file(). KASan report like below: [ 14.057131] ================================================================== [ 14.059161] BUG: KASAN: use-after-free in unix_get_socket+0x10/0x90 [ 14.060975] Read of size 8 at addr ffff88800b09cf20 by task kworker/u8:2/45 [ 14.062684] [ 14.062768] CPU: 2 PID: 45 Comm: kworker/u8:2 Not tainted 6.1.0-rc4 #1 [ 14.063099] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 [ 14.063666] Workqueue: events_unbound io_ring_exit_work [ 14.063936] Call Trace: [ 14.064065] [ 14.064175] dump_stack_lvl+0x34/0x48 [ 14.064360] print_report+0x172/0x475 [ 14.064547] ? _raw_spin_lock_irq+0x83/0xe0 [ 14.064758] ? __virt_addr_valid+0xef/0x170 [ 14.064975] ? unix_get_socket+0x10/0x90 [ 14.065167] kasan_report+0xad/0x130 [ 14.065353] ? unix_get_socket+0x10/0x90 [ 14.065553] unix_get_socket+0x10/0x90 [ 14.065744] __io_sqe_files_unregister+0x87/0x1e0 [ 14.065989] ? io_rsrc_refs_drop+0x1c/0xd0 [ 14.066199] io_ring_exit_work+0x388/0x6a5 [ 14.066410] ? io_uring_try_cancel_requests+0x5bf/0x5bf [ 14.066674] ? try_to_wake_up+0xdb/0x910 [ 14.066873] ? virt_to_head_page+0xbe/0xbe [ 14.067080] ? __schedule+0x574/0xd20 [ 14.067273] ? read_word_at_a_time+0xe/0x20 [ 14.067492] ? strscpy+0xb5/0x190 [ 14.067665] process_one_work+0x423/0x710 [ 14.067879] worker_thread+0x2a2/0x6f0 [ 14.068073] ? process_one_work+0x710/0x710 [ 14.068284] kthread+0x163/0x1a0 [ 14.068454] ? kthread_complete_and_exit+0x20/0x20 [ 14.068697] ret_from_fork+0x22/0x30 [ 14.068886] [ 14.069000] [ 14.069088] Allocated by task 289: [ 14.069269] kasan_save_stack+0x1e/0x40 [ 14.069463] kasan_set_track+0x21/0x30 [ 14.069652] __kasan_slab_alloc+0x58/0x70 [ 14.069899] kmem_cache_alloc+0xc5/0x200 [ 14.070100] __alloc_file+0x20/0x160 [ 14.070283] alloc_empty_file+0x3b/0xc0 [ 14.070479] path_openat+0xc3/0x1770 [ 14.070689] do_filp_open+0x150/0x270 [ 14.070888] do_sys_openat2+0x113/0x270 [ 14.071081] __x64_sys_openat+0xc8/0x140 [ 14.071283] do_syscall_64+0x3b/0x90 [ 14.071466] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 14.071791] [ 14.071874] Freed by task 0: [ 14.072027] kasan_save_stack+0x1e/0x40 [ 14.072224] kasan_set_track+0x21/0x30 [ 14.072415] kasan_save_free_info+0x2a/0x50 [ 14.072627] __kasan_slab_free+0x106/0x190 [ 14.072858] kmem_cache_free+0x98/0x340 [ 14.073075] rcu_core+0x427/0xe50 [ 14.073249] __do_softirq+0x110/0x3cd [ 14.073440] [ 14.073523] Last potentially related work creation: [ 14.073801] kasan_save_stack+0x1e/0x40 [ 14.074017] __kasan_record_aux_stack+0x97/0xb0 [ 14.074264] call_rcu+0x41/0x550 [ 14.074436] task_work_run+0xf4/0x170 [ 14.074619] exit_to_user_mode_prepare+0x113/0x120 [ 14.074858] syscall_exit_to_user_mode+0x1d/0x40 [ 14.075092] do_syscall_64+0x48/0x90 [ 14.075272] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 14.075529] [ 14.075612] Second to last potentially related work creation: [ 14.075900] kasan_save_stack+0x1e/0x40 [ 14.076098] __kasan_record_aux_stack+0x97/0xb0 [ 14.076325] task_work_add+0x72/0x1b0 [ 14.076512] fput+0x65/0xc0 [ 14.076657] filp_close+0x8e/0xa0 [ 14.076825] __x64_sys_close+0x15/0x50 [ 14.077019] do_syscall_64+0x3b/0x90 [ 14.077199] entry_SYSCALL_64_after_hwframe+0x63/0xcd [ 14.077448] [ 14.077530] The buggy address belongs to the object at ffff88800b09cf00 [ 14.077530] which belongs to the cache filp of size 232 [ 14.078105] The buggy address is located 32 bytes inside of [ 14.078105] 232-byte region [ffff88800b09cf00, ffff88800b09cfe8) [ 14.078685] [ 14.078771] The buggy address belongs to the physical page: [ 14.079046] page:000000001bd520e7 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88800b09de00 pfn:0xb09c [ 14.079575] head:000000001bd520e7 order:1 compound_mapcount:0 compound_pincount:0 [ 14.079946] flags: 0x100000000010200(slab|head|node=0|zone=1) [ 14.080244] raw: 0100000000010200 0000000000000000 dead000000000001 ffff88800493cc80 [ 14.080629] raw: ffff88800b09de00 0000000080190018 00000001ffffffff 0000000000000000 [ 14.081016] page dumped because: kasan: bad access detected [ 14.081293] [ 14.081376] Memory state around the buggy address: [ 14.081618] ffff88800b09ce00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 [ 14.081974] ffff88800b09ce80: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc [ 14.082336] >ffff88800b09cf00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 14.082690] ^ [ 14.082909] ffff88800b09cf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc [ 14.083266] ffff88800b09d000: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb [ 14.083622] ================================================================== The actual tracing of this bug is shown below: commit 8c71fe750215 ("io_uring: ensure fput() called correspondingly when direct install fails") adds an additional fput() in io_fixed_fd_install() when io_file_bitmap_get() returns error values. In that case, the routine will never make it to io_install_fixed_file() due to an early return. static int io_fixed_fd_install(...) { if (alloc_slot) { ... ret = io_file_bitmap_get(ctx); if (unlikely(ret < 0)) { io_ring_submit_unlock(ctx, issue_flags); fput(file); return ret; } ... } ... ret = io_install_fixed_file(req, file, issue_flags, file_slot); ... } In the above scenario, the reference is okay as io_fixed_fd_install() ensures the fput() is called when something bad happens, either via bitmap or via inner io_install_fixed_file(). However, the commit 61c1b44a21d7 ("io_uring: fix deadlock on iowq file slot alloc") breaks the balance because it places fput() into the common path for both io_file_bitmap_get() and io_install_fixed_file(). Since io_install_fixed_file() handles the fput() itself, the reference underflow come across then. There are some extra commits make the current code into io_fixed_fd_install() -> __io_fixed_fd_install() -> io_install_fixed_file() However, the fact that there is an extra fput() is called if io_install_fixed_file() calls fput(). Traversing through the code, I find that the existing two callers to __io_fixed_fd_install(): io_fixed_fd_install() and io_msg_send_fd() have fput() when handling error return, this patch simply removes the fput() in io_install_fixed_file() to fix the bug. Fixes: 61c1b44a21d7 ("io_uring: fix deadlock on iowq file slot alloc") Signed-off-by: Lin Ma --- V0->V1: fix typos V1->V2: add crash stack io_uring/filetable.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/io_uring/filetable.c b/io_uring/filetable.c index 7b473259f3f4..68dfc6936aa7 100644 --- a/io_uring/filetable.c +++ b/io_uring/filetable.c @@ -101,8 +101,6 @@ static int io_install_fixed_file(struct io_ring_ctx *ctx, struct file *file, err: if (needs_switch) io_rsrc_node_switch(ctx, ctx->file_data); - if (ret) - fput(file); return ret; }