IB/iser: Fix connection teardown race condition
Under heavy iser target(scst) start/stop stress during login/logout on iser intitiator side happened trace call provided below. The function iscsi_iser_slave_alloc iser_conn pointer could be NULL, due to the fact that function iscsi_iser_conn_stop can be called before and free iser connection. Let's protect that flow by introducing global mutex. BUG: unable to handle kernel paging request at 0000000000001018 IP: [<ffffffffc0426f7e>] iscsi_iser_slave_alloc+0x1e/0x50 [ib_iser] Call Trace: ? scsi_alloc_sdev+0x242/0x300 scsi_probe_and_add_lun+0x9e1/0xea0 ? kfree_const+0x21/0x30 ? kobject_set_name_vargs+0x76/0x90 ? __pm_runtime_resume+0x5b/0x70 __scsi_scan_target+0xf6/0x250 scsi_scan_target+0xea/0x100 iscsi_user_scan_session.part.13+0x101/0x130 [scsi_transport_iscsi] ? iscsi_user_scan_session.part.13+0x130/0x130 [scsi_transport_iscsi] iscsi_user_scan_session+0x1e/0x30 [scsi_transport_iscsi] device_for_each_child+0x50/0x90 iscsi_user_scan+0x44/0x60 [scsi_transport_iscsi] store_scan+0xa8/0x100 ? common_file_perm+0x5d/0x1c0 dev_attr_store+0x18/0x30 sysfs_kf_write+0x37/0x40 kernfs_fop_write+0x12c/0x1c0 __vfs_write+0x18/0x40 vfs_write+0xb5/0x1a0 SyS_write+0x55/0xc0 Fixes: 318d311e ("iser: Accept arbitrary sg lists mapping if the device supports it") Cc: <stable@vger.kernel.org> # v4.5+ Signed-off-by: Vladimir Neyelov <vladimirn@mellanox.com> Signed-off-by: Leon Romanovsky <leon@kernel.org> Reviewed-by: Sagi Grimberg <sagi@grimbeg.me> Signed-off-by: Doug Ledford <dledford@redhat.com>
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