From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 134AAC6778A for ; Tue, 24 Jul 2018 15:12:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCF3F20856 for ; Tue, 24 Jul 2018 15:12:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CCF3F20856 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=I-love.SAKURA.ne.jp Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388467AbeGXQTH (ORCPT ); Tue, 24 Jul 2018 12:19:07 -0400 Received: from www262.sakura.ne.jp ([202.181.97.72]:34186 "EHLO www262.sakura.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388322AbeGXQTH (ORCPT ); Tue, 24 Jul 2018 12:19:07 -0400 Received: from fsav301.sakura.ne.jp (fsav301.sakura.ne.jp [153.120.85.132]) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTP id w6OFBWeU088805; Wed, 25 Jul 2018 00:11:32 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Received: from www262.sakura.ne.jp (202.181.97.72) by fsav301.sakura.ne.jp (F-Secure/fsigk_smtp/530/fsav301.sakura.ne.jp); Wed, 25 Jul 2018 00:11:32 +0900 (JST) X-Virus-Status: clean(F-Secure/fsigk_smtp/530/fsav301.sakura.ne.jp) Received: from [192.168.1.8] (softbank126074194044.bbtec.net [126.74.194.44]) (authenticated bits=0) by www262.sakura.ne.jp (8.15.2/8.15.2) with ESMTPSA id w6OFBVk8088801 (version=TLSv1.2 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 25 Jul 2018 00:11:31 +0900 (JST) (envelope-from penguin-kernel@I-love.SAKURA.ne.jp) Subject: Re: [PATCH v3 5/8] proc/kcore: hold lock during read To: Omar Sandoval Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Alexey Dobriyan , Eric Biederman , James Morse , Bhupesh Sharma , kernel-team@fb.com References: From: Tetsuo Handa Message-ID: <7f905293-5c30-f001-987f-03caf8f36737@I-love.SAKURA.ne.jp> Date: Wed, 25 Jul 2018 00:11:26 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/07/19 7:58, Omar Sandoval wrote: > From: Omar Sandoval > > Now that we're using an rwsem, we can hold it during the entirety of > read_kcore() and have a common return path. This is preparation for the > next change. > > Signed-off-by: Omar Sandoval > --- > fs/proc/kcore.c | 70 ++++++++++++++++++++++++++++--------------------- > 1 file changed, 40 insertions(+), 30 deletions(-) > > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c > index 95aa988c5b5d..e317ac890871 100644 > --- a/fs/proc/kcore.c > +++ b/fs/proc/kcore.c > @@ -440,19 +440,18 @@ static ssize_t > read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > { > char *buf = file->private_data; > - ssize_t acc = 0; > size_t size, tsz; > size_t elf_buflen; > int nphdr; > unsigned long start; > + size_t orig_buflen = buflen; > + int ret = 0; > > down_read(&kclist_lock); (...snipped...) > +out: > + up_write(&kclist_lock); Oops. This needs to be up_read(). > + if (ret) > + return ret; > + return orig_buflen - buflen; > } > [ 43.508922] ------------[ cut here ]------------ [ 43.509931] DEBUG_LOCKS_WARN_ON(sem->owner != get_current()) [ 43.509940] WARNING: CPU: 0 PID: 7933 at kernel/locking/rwsem.c:133 up_write+0x75/0x80 [ 43.512792] Modules linked in: pcspkr sg vmw_vmci i2c_piix4 sd_mod ata_generic pata_acpi vmwgfx drm_kms_helper syscopyarea ahci sysfillrect libahci sysimgblt fb_sys_fops mptspi ata_piix ttm scsi_transport_spi mptscsih drm e1000 mptbase libata i2c_core serio_raw ipv6 crc_ccitt [ 43.517692] CPU: 0 PID: 7933 Comm: kexec Not tainted 4.18.0-rc6-next-20180724+ #715 [ 43.519237] Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/19/2017 [ 43.521498] RIP: 0010:up_write+0x75/0x80 [ 43.522391] Code: 00 5b c3 e8 0d 03 3a 00 85 c0 74 d9 83 3d 6a e4 10 02 00 75 d0 48 c7 c6 c8 2f e0 81 48 c7 c7 a3 e3 de 81 31 c0 e8 fb 8d fa ff <0f> 0b eb b7 0f 1f 80 00 00 00 00 8b 05 42 3e 06 02 53 48 89 fb 85 [ 43.526253] RSP: 0018:ffffc90007ec7bc8 EFLAGS: 00010282 [ 43.527303] RAX: 0000000000000000 RBX: ffffffff8207b5e0 RCX: 0000000000000006 [ 43.528874] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88013ba15b70 [ 43.530496] RBP: ffffc90007ec7e28 R08: 0000000000000000 R09: 0000000000000001 [ 43.532007] R10: 0000000000000000 R11: 292928746e657272 R12: ffffffff8207b660 [ 43.533448] R13: 0000000000000000 R14: 0000000000000000 R15: 000000000000e000 [ 43.534969] FS: 00007fdd6e0c0740(0000) GS:ffff88013ba00000(0000) knlGS:0000000000000000 [ 43.536623] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 43.537943] CR2: 00000000017dc000 CR3: 00000001376b5006 CR4: 00000000001606f0 [ 43.539608] Call Trace: [ 43.540154] read_kcore+0x81/0x630 [ 43.540932] proc_reg_read+0x34/0x60 [ 43.541722] __vfs_read+0x2e/0x160 [ 43.542450] vfs_read+0x84/0x130 [ 43.543166] ksys_read+0x50/0xc0 [ 43.543856] do_syscall_64+0x4f/0x1f0 [ 43.544684] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 43.545909] RIP: 0033:0x7fdd6d798c70 [ 43.546688] Code: 0b 31 c0 48 83 c4 08 e9 be fe ff ff 48 8d 3d 07 b9 09 00 e8 52 8a 02 00 66 90 83 3d 2d c3 2d 00 00 75 10 b8 00 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 4e cc 01 00 48 89 04 24 [ 43.550607] RSP: 002b:00007fffe5207428 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 [ 43.552192] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fdd6d798c70 [ 43.553711] RDX: 0000000000010000 RSI: 00000000017cd840 RDI: 0000000000000004 [ 43.555240] RBP: 0000000000010000 R08: 0000000000000001 R09: 0000000000010000 [ 43.556779] R10: 0000000000000079 R11: 0000000000000246 R12: 0000000000000004 [ 43.558284] R13: 00000000017cd840 R14: 00007fffe52074d8 R15: 00007fffe52076c0 [ 43.559809] irq event stamp: 25471 [ 43.560597] hardirqs last enabled at (25471): [] restore_regs_and_return_to_kernel+0x0/0x2a [ 43.562821] hardirqs last disabled at (25470): [] error_exit+0x6/0x20 [ 43.564515] softirqs last enabled at (24962): [] __do_softirq+0x1db/0x48e [ 43.566308] softirqs last disabled at (24955): [] irq_exit+0xcd/0xe0 [ 43.567982] ---[ end trace 0140237dd1b1be70 ]---