Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 43E74C433F5 for ; Mon, 3 Jan 2022 14:22:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233522AbiACOWy (ORCPT ); Mon, 3 Jan 2022 09:22:54 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37556 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233514AbiACOWc (ORCPT ); Mon, 3 Jan 2022 09:22:32 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 796DBC061398; Mon, 3 Jan 2022 06:22:32 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 173816112C; Mon, 3 Jan 2022 14:22:32 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E0495C36AED; Mon, 3 Jan 2022 14:22:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1641219751; bh=Hur8GOKGyMREdqvAx+nt+sewgTNXhlwSEk8vpVxhjSs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=zq2md8OGQme0KHQK6xj2xarVc3yvfdmoQa3mubsNclmSyGDK7XAcQNi9KPM95TcvB wyRCSAQVOYellwiivxUO/kqNbs2apbastzoRqEMv3ohr58WzUUhFvhY5Cvt58+71BC ZQ5bCtMbeIZW1oMD2MIUJVNQjIWORwkQPu5vTsOY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vincent Pelletier Subject: [PATCH 4.9 09/13] usb: gadget: f_fs: Clear ffs_eventfd in ffs_data_clear. Date: Mon, 3 Jan 2022 15:21:25 +0100 Message-Id: <20220103142052.261456372@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220103142051.979780231@linuxfoundation.org> References: <20220103142051.979780231@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vincent Pelletier commit b1e0887379422975f237d43d8839b751a6bcf154 upstream. ffs_data_clear is indirectly called from both ffs_fs_kill_sb and ffs_ep0_release, so it ends up being called twice when userland closes ep0 and then unmounts f_fs. If userland provided an eventfd along with function's USB descriptors, it ends up calling eventfd_ctx_put as many times, causing a refcount underflow. NULL-ify ffs_eventfd to prevent these extraneous eventfd_ctx_put calls. Also, set epfiles to NULL right after de-allocating it, for readability. For completeness, ffs_data_clear actually ends up being called thrice, the last call being before the whole ffs structure gets freed, so when this specific sequence happens there is a second underflow happening (but not being reported): /sys/kernel/debug/tracing# modprobe usb_f_fs /sys/kernel/debug/tracing# echo ffs_data_clear > set_ftrace_filter /sys/kernel/debug/tracing# echo function > current_tracer /sys/kernel/debug/tracing# echo 1 > tracing_on (setup gadget, run and kill function userland process, teardown gadget) /sys/kernel/debug/tracing# echo 0 > tracing_on /sys/kernel/debug/tracing# cat trace smartcard-openp-436 [000] ..... 1946.208786: ffs_data_clear <-ffs_data_closed smartcard-openp-431 [000] ..... 1946.279147: ffs_data_clear <-ffs_data_closed smartcard-openp-431 [000] .n... 1946.905512: ffs_data_clear <-ffs_data_put Warning output corresponding to above trace: [ 1946.284139] WARNING: CPU: 0 PID: 431 at lib/refcount.c:28 refcount_warn_saturate+0x110/0x15c [ 1946.293094] refcount_t: underflow; use-after-free. [ 1946.298164] Modules linked in: usb_f_ncm(E) u_ether(E) usb_f_fs(E) hci_uart(E) btqca(E) btrtl(E) btbcm(E) btintel(E) bluetooth(E) nls_ascii(E) nls_cp437(E) vfat(E) fat(E) bcm2835_v4l2(CE) bcm2835_mmal_vchiq(CE) videobuf2_vmalloc(E) videobuf2_memops(E) sha512_generic(E) videobuf2_v4l2(E) sha512_arm(E) videobuf2_common(E) videodev(E) cpufreq_dt(E) snd_bcm2835(CE) brcmfmac(E) mc(E) vc4(E) ctr(E) brcmutil(E) snd_soc_core(E) snd_pcm_dmaengine(E) drbg(E) snd_pcm(E) snd_timer(E) snd(E) soundcore(E) drm_kms_helper(E) cec(E) ansi_cprng(E) rc_core(E) syscopyarea(E) raspberrypi_cpufreq(E) sysfillrect(E) sysimgblt(E) cfg80211(E) max17040_battery(OE) raspberrypi_hwmon(E) fb_sys_fops(E) regmap_i2c(E) ecdh_generic(E) rfkill(E) ecc(E) bcm2835_rng(E) rng_core(E) vchiq(CE) leds_gpio(E) libcomposite(E) fuse(E) configfs(E) ip_tables(E) x_tables(E) autofs4(E) ext4(E) crc16(E) mbcache(E) jbd2(E) crc32c_generic(E) sdhci_iproc(E) sdhci_pltfm(E) sdhci(E) [ 1946.399633] CPU: 0 PID: 431 Comm: smartcard-openp Tainted: G C OE 5.15.0-1-rpi #1 Debian 5.15.3-1 [ 1946.417950] Hardware name: BCM2835 [ 1946.425442] Backtrace: [ 1946.432048] [] (dump_backtrace) from [] (show_stack+0x20/0x24) [ 1946.448226] r7:00000009 r6:0000001c r5:c04a948c r4:c0a64e2c [ 1946.458412] [] (show_stack) from [] (dump_stack+0x28/0x30) [ 1946.470380] [] (dump_stack) from [] (__warn+0xe8/0x154) [ 1946.482067] r5:c04a948c r4:c0a71dc8 [ 1946.490184] [] (__warn) from [] (warn_slowpath_fmt+0xa0/0xe4) [ 1946.506758] r7:00000009 r6:0000001c r5:c0a71dc8 r4:c0a71e04 [ 1946.517070] [] (warn_slowpath_fmt) from [] (refcount_warn_saturate+0x110/0x15c) [ 1946.535309] r8:c0100224 r7:c0dfcb84 r6:ffffffff r5:c3b84c00 r4:c24a17c0 [ 1946.546708] [] (refcount_warn_saturate) from [] (eventfd_ctx_put+0x48/0x74) [ 1946.564476] [] (eventfd_ctx_put) from [] (ffs_data_clear+0xd0/0x118 [usb_f_fs]) [ 1946.582664] r5:c3b84c00 r4:c2695b00 [ 1946.590668] [] (ffs_data_clear [usb_f_fs]) from [] (ffs_data_closed+0x9c/0x150 [usb_f_fs]) [ 1946.609608] r5:bf54d014 r4:c2695b00 [ 1946.617522] [] (ffs_data_closed [usb_f_fs]) from [] (ffs_fs_kill_sb+0x2c/0x30 [usb_f_fs]) [ 1946.636217] r7:c0dfcb84 r6:c3a12260 r5:bf54d014 r4:c229f000 [ 1946.646273] [] (ffs_fs_kill_sb [usb_f_fs]) from [] (deactivate_locked_super+0x54/0x9c) [ 1946.664893] r5:bf54d014 r4:c229f000 [ 1946.672921] [] (deactivate_locked_super) from [] (deactivate_super+0x60/0x64) [ 1946.690722] r5:c2a09000 r4:c229f000 [ 1946.698706] [] (deactivate_super) from [] (cleanup_mnt+0xe4/0x14c) [ 1946.715553] r5:c2a09000 r4:00000000 [ 1946.723528] [] (cleanup_mnt) from [] (__cleanup_mnt+0x1c/0x20) [ 1946.739922] r7:c0dfcb84 r6:c3a12260 r5:c3a126fc r4:00000000 [ 1946.750088] [] (__cleanup_mnt) from [] (task_work_run+0x84/0xb8) [ 1946.766602] [] (task_work_run) from [] (do_work_pending+0x470/0x56c) [ 1946.783540] r7:5ac3c35a r6:c0d0424c r5:c200bfb0 r4:c200a000 [ 1946.793614] [] (do_work_pending) from [] (slow_work_pending+0xc/0x20) [ 1946.810553] Exception stack(0xc200bfb0 to 0xc200bff8) [ 1946.820129] bfa0: 00000000 00000000 000000aa b5e21430 [ 1946.837104] bfc0: bef867a0 00000001 bef86840 00000034 bef86838 bef86790 bef86794 bef867a0 [ 1946.854125] bfe0: 00000000 bef86798 b67b7a1c b6d626a4 60000010 b5a23760 [ 1946.865335] r10:00000000 r9:c200a000 r8:c0100224 r7:00000034 r6:bef86840 r5:00000001 [ 1946.881914] r4:bef867a0 [ 1946.888793] ---[ end trace 7387f2a9725b28d0 ]--- Fixes: 5e33f6fdf735 ("usb: gadget: ffs: add eventfd notification about ffs events") Cc: stable Signed-off-by: Vincent Pelletier Link: https://lore.kernel.org/r/f79eeea29f3f98de6782a064ec0f7351ad2f598f.1639793920.git.plr.vincent@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/usb/gadget/function/f_fs.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -1667,11 +1667,15 @@ static void ffs_data_clear(struct ffs_da BUG_ON(ffs->gadget); - if (ffs->epfiles) + if (ffs->epfiles) { ffs_epfiles_destroy(ffs->epfiles, ffs->eps_count); + ffs->epfiles = NULL; + } - if (ffs->ffs_eventfd) + if (ffs->ffs_eventfd) { eventfd_ctx_put(ffs->ffs_eventfd); + ffs->ffs_eventfd = NULL; + } kfree(ffs->raw_descs_data); kfree(ffs->raw_strings); @@ -1684,7 +1688,6 @@ static void ffs_data_reset(struct ffs_da ffs_data_clear(ffs); - ffs->epfiles = NULL; ffs->raw_descs_data = NULL; ffs->raw_descs = NULL; ffs->raw_strings = NULL;