From: "Ewan D. Milne" emilne@redhat.com
[ Upstream commit f9279c968c257ee39b0d7bd2571a4d231a67bcc1 ]
The addition of the STARGET_REMOVE state had the side effect of introducing a race condition that can cause a crash.
scsi_target_reap_ref_release() checks the starget->state to see if it still in STARGET_CREATED, and if so, skips calling transport_remove_device() and device_del(), because the starget->state is only set to STARGET_RUNNING after scsi_target_add() has called device_add() and transport_add_device().
However, if an rport loss occurs while a target is being scanned, it can happen that scsi_remove_target() will be called while the starget is still in the STARGET_CREATED state. In this case, the starget->state will be set to STARGET_REMOVE, and as a result, scsi_target_reap_ref_release() will take the wrong path. The end result is a panic:
[ 1255.356653] Oops: 0000 [#1] SMP [ 1255.360154] Modules linked in: x86_pkg_temp_thermal kvm_intel kvm irqbypass crc32c_intel ghash_clmulni_i [ 1255.393234] CPU: 5 PID: 149 Comm: kworker/u96:4 Tainted: G W 4.11.0+ #8 [ 1255.401879] Hardware name: Dell Inc. PowerEdge R320/08VT7V, BIOS 2.0.22 11/19/2013 [ 1255.410327] Workqueue: scsi_wq_6 fc_scsi_scan_rport [scsi_transport_fc] [ 1255.417720] task: ffff88060ca8c8c0 task.stack: ffffc900048a8000 [ 1255.424331] RIP: 0010:kernfs_find_ns+0x13/0xc0 [ 1255.429287] RSP: 0018:ffffc900048abbf0 EFLAGS: 00010246 [ 1255.435123] RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 [ 1255.443083] RDX: 0000000000000000 RSI: ffffffff8188d659 RDI: 0000000000000000 [ 1255.451043] RBP: ffffc900048abc10 R08: 0000000000000000 R09: 0000012433fe0025 [ 1255.459005] R10: 0000000025e5a4b5 R11: 0000000025e5a4b5 R12: ffffffff8188d659 [ 1255.466972] R13: 0000000000000000 R14: ffff8805f55e5088 R15: 0000000000000000 [ 1255.474931] FS: 0000000000000000(0000) GS:ffff880616b40000(0000) knlGS:0000000000000000 [ 1255.483959] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1255.490370] CR2: 0000000000000068 CR3: 0000000001c09000 CR4: 00000000000406e0 [ 1255.498332] Call Trace: [ 1255.501058] kernfs_find_and_get_ns+0x31/0x60 [ 1255.505916] sysfs_unmerge_group+0x1d/0x60 [ 1255.510498] dpm_sysfs_remove+0x22/0x60 [ 1255.514783] device_del+0xf4/0x2e0 [ 1255.518577] ? device_remove_file+0x19/0x20 [ 1255.523241] attribute_container_class_device_del+0x1a/0x20 [ 1255.529457] transport_remove_classdev+0x4e/0x60 [ 1255.534607] ? transport_add_class_device+0x40/0x40 [ 1255.540046] attribute_container_device_trigger+0xb0/0xc0 [ 1255.546069] transport_remove_device+0x15/0x20 [ 1255.551025] scsi_target_reap_ref_release+0x25/0x40 [ 1255.556467] scsi_target_reap+0x2e/0x40 [ 1255.560744] __scsi_scan_target+0xaa/0x5b0 [ 1255.565312] scsi_scan_target+0xec/0x100 [ 1255.569689] fc_scsi_scan_rport+0xb1/0xc0 [scsi_transport_fc] [ 1255.576099] process_one_work+0x14b/0x390 [ 1255.580569] worker_thread+0x4b/0x390 [ 1255.584651] kthread+0x109/0x140 [ 1255.588251] ? rescuer_thread+0x330/0x330 [ 1255.592730] ? kthread_park+0x60/0x60 [ 1255.596815] ret_from_fork+0x29/0x40 [ 1255.600801] Code: 24 08 48 83 42 40 01 5b 41 5c 5d c3 66 66 66 2e 0f 1f 84 00 00 00 00 00 66 66 66 66 90 [ 1255.621876] RIP: kernfs_find_ns+0x13/0xc0 RSP: ffffc900048abbf0 [ 1255.628479] CR2: 0000000000000068 [ 1255.632756] ---[ end trace 34a69ba0477d036f ]---
Fix this by adding another scsi_target state STARGET_CREATED_REMOVE to distinguish this case.
Fixes: f05795d3d771 ("scsi: Add intermediate STARGET_REMOVE state to scsi_target_state") Reported-by: David Jeffery djeffery@redhat.com Signed-off-by: Ewan D. Milne emilne@redhat.com Cc: stable@vger.kernel.org Reviewed-by: Laurence Oberman loberman@redhat.com Tested-by: Laurence Oberman loberman@redhat.com Reviewed-by: Johannes Thumshirn jthumshirn@suse.de Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/scsi_scan.c | 5 +++-- drivers/scsi/scsi_sysfs.c | 8 ++++++-- include/scsi/scsi_device.h | 1 + 3 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c index 692445bcca6f..850ddc5fac04 100644 --- a/drivers/scsi/scsi_scan.c +++ b/drivers/scsi/scsi_scan.c @@ -381,11 +381,12 @@ static void scsi_target_reap_ref_release(struct kref *kref) = container_of(kref, struct scsi_target, reap_ref);
/* - * if we get here and the target is still in the CREATED state that + * if we get here and the target is still in a CREATED state that * means it was allocated but never made visible (because a scan * turned up no LUNs), so don't call device_del() on it. */ - if (starget->state != STARGET_CREATED) { + if ((starget->state != STARGET_CREATED) && + (starget->state != STARGET_CREATED_REMOVE)) { transport_remove_device(&starget->dev); device_del(&starget->dev); } diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index 8db0c48943d6..085e470d1c49 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -1212,11 +1212,15 @@ void scsi_remove_target(struct device *dev) spin_lock_irqsave(shost->host_lock, flags); list_for_each_entry(starget, &shost->__targets, siblings) { if (starget->state == STARGET_DEL || - starget->state == STARGET_REMOVE) + starget->state == STARGET_REMOVE || + starget->state == STARGET_CREATED_REMOVE) continue; if (starget->dev.parent == dev || &starget->dev == dev) { kref_get(&starget->reap_ref); - starget->state = STARGET_REMOVE; + if (starget->state == STARGET_CREATED) + starget->state = STARGET_CREATED_REMOVE; + else + starget->state = STARGET_REMOVE; spin_unlock_irqrestore(shost->host_lock, flags); __scsi_remove_target(starget); scsi_target_reap(starget); diff --git a/include/scsi/scsi_device.h b/include/scsi/scsi_device.h index 293b9a7f53bc..fb53a94a5e8b 100644 --- a/include/scsi/scsi_device.h +++ b/include/scsi/scsi_device.h @@ -240,6 +240,7 @@ enum scsi_target_state { STARGET_CREATED = 1, STARGET_RUNNING, STARGET_REMOVE, + STARGET_CREATED_REMOVE, STARGET_DEL, };