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signed) header.d=none;dmarc=none action=none header.from=citrix.com; Date: Thu, 12 May 2022 15:59:42 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: Jason Andryuk Cc: Marek =?utf-8?Q?Marczykowski-G=C3=B3recki?= , xen-devel Subject: Re: xen-blkfront crash on xl block-detach of not fully attached device Message-ID: References: Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-ClientProxiedBy: LO4P123CA0089.GBRP123.PROD.OUTLOOK.COM (2603:10a6:600:190::22) To DS7PR03MB5608.namprd03.prod.outlook.com (2603:10b6:5:2c9::18) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 8e8045dd-e166-4f03-0a2e-08da341fac49 X-MS-TrafficTypeDiagnostic: BL0PR03MB4097:EE_ X-Microsoft-Antispam-PRVS: X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: aNqAJ7UErMS6oVsg7CfmXdmSrN/mPEBgoZ3kwj5KdMk7vAQPZst1GA3H8skOoy9ko06fnFRBhdqB3d6wFf8Y/Q== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BL0PR03MB4097 On Thu, May 12, 2022 at 08:47:01AM -0400, Jason Andryuk wrote: > On Wed, May 11, 2022 at 3:25 PM Marek Marczykowski-Górecki > wrote: > > > > Hi, > > > > The reproducer is trivial: > > > > [user@dom0 ~]$ sudo xl block-attach work backend=sys-usb vdev=xvdi target=/dev/sdz > > [user@dom0 ~]$ xl block-list work > > Vdev BE handle state evt-ch ring-ref BE-path > > 51712 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51712 > > 51728 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51728 > > 51744 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51744 > > 51760 0 241 4 -1 -1 /local/domain/0/backend/vbd/241/51760 > > 51840 3 241 3 -1 -1 /local/domain/3/backend/vbd/241/51840 > > ^ note state, the /dev/sdz doesn't exist in the backend > > > > [user@dom0 ~]$ sudo xl block-detach work xvdi > > [user@dom0 ~]$ xl block-list work > > Vdev BE handle state evt-ch ring-ref BE-path > > work is an invalid domain identifier > > > > And its console has: > > > > BUG: kernel NULL pointer dereference, address: 0000000000000050 > > #PF: supervisor read access in kernel mode > > #PF: error_code(0x0000) - not-present page > > PGD 80000000edebb067 P4D 80000000edebb067 PUD edec2067 PMD 0 > > Oops: 0000 [#1] PREEMPT SMP PTI > > CPU: 1 PID: 52 Comm: xenwatch Not tainted 5.16.18-2.43.fc32.qubes.x86_64 #1 > > RIP: 0010:blk_mq_stop_hw_queues+0x5/0x40 > > Code: 00 48 83 e0 fd 83 c3 01 48 89 85 a8 00 00 00 41 39 5c 24 50 77 c0 5b 5d 41 5c 41 5d c3 c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 <8b> 47 50 85 c0 74 32 41 54 49 89 fc 55 53 31 db 49 8b 44 24 48 48 > > RSP: 0018:ffffc90000bcfe98 EFLAGS: 00010293 > > RAX: ffffffffc0008370 RBX: 0000000000000005 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000000 > > RBP: ffff88800775f000 R08: 0000000000000001 R09: ffff888006e620b8 > > R10: ffff888006e620b0 R11: f000000000000000 R12: ffff8880bff39000 > > R13: ffff8880bff39000 R14: 0000000000000000 R15: ffff88800604be00 > > FS: 0000000000000000(0000) GS:ffff8880f3300000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000000050 CR3: 00000000e932e002 CR4: 00000000003706e0 > > Call Trace: > > > > blkback_changed+0x95/0x137 [xen_blkfront] > > ? read_reply+0x160/0x160 > > xenwatch_thread+0xc0/0x1a0 > > ? do_wait_intr_irq+0xa0/0xa0 > > kthread+0x16b/0x190 > > ? set_kthread_struct+0x40/0x40 > > ret_from_fork+0x22/0x30 > > > > Modules linked in: snd_seq_dummy snd_hrtimer snd_seq snd_seq_device snd_timer snd soundcore ipt_REJECT nf_reject_ipv4 xt_state xt_conntrack nft_counter nft_chain_nat xt_MASQUERADE nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_compat nf_tables nfnetlink intel_rapl_msr intel_rapl_common crct10dif_pclmul crc32_pclmul crc32c_intel ghash_clmulni_intel xen_netfront pcspkr xen_scsiback target_core_mod xen_netback xen_privcmd xen_gntdev xen_gntalloc xen_blkback xen_evtchn ipmi_devintf ipmi_msghandler fuse bpf_preload ip_tables overlay xen_blkfront > > CR2: 0000000000000050 > > ---[ end trace 7bc9597fd06ae89d ]--- > > RIP: 0010:blk_mq_stop_hw_queues+0x5/0x40 > > Code: 00 48 83 e0 fd 83 c3 01 48 89 85 a8 00 00 00 41 39 5c 24 50 77 c0 5b 5d 41 5c 41 5d c3 c3 0f 1f 80 00 00 00 00 0f 1f 44 00 00 <8b> 47 50 85 c0 74 32 41 54 49 89 fc 55 53 31 db 49 8b 44 24 48 48 > > RSP: 0018:ffffc90000bcfe98 EFLAGS: 00010293 > > RAX: ffffffffc0008370 RBX: 0000000000000005 RCX: 0000000000000000 > > RDX: 0000000000000000 RSI: 0000000000000005 RDI: 0000000000000000 > > RBP: ffff88800775f000 R08: 0000000000000001 R09: ffff888006e620b8 > > R10: ffff888006e620b0 R11: f000000000000000 R12: ffff8880bff39000 > > R13: ffff8880bff39000 R14: 0000000000000000 R15: ffff88800604be00 > > FS: 0000000000000000(0000) GS:ffff8880f3300000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 0000000000000050 CR3: 00000000e932e002 CR4: 00000000003706e0 > > Kernel panic - not syncing: Fatal exception > > Kernel Offset: disabled > > This looks like it may be blkfront_closing() calling > blk_mq_stop_hw_queues() with info->rq == NULL. info->rq is only > assigned in blkfront_connect(), which is called for state 4, but your > vbd never made it through there. It seems like blkfront_closing() > should NULL check info->rq and info->gd before using them. Care to send a patch? :) Thanks, Roger.