scsi: iscsi: Have abort handler get ref to conn

mainline inclusion
from mainline-v5.14-rc1
commit d39df158
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I9R4O4
CVE: CVE-2021-47427

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d39df158518ccc3bf24ee18082b5e100c8f014aa

--------------------------------

If SCSI midlayer is aborting a task when we are tearing down the conn we
could free the conn while the abort thread is accessing the conn. This has
the abort handler get a ref to the conn so it won't be freed from under it.

Note: this is not needed for device/target reset because we are holding the
eh_mutex when accessing the conn.

Link: https://lore.kernel.org/r/20210525181821.7617-12-michael.christie@oracle.com


Reviewed-by: Lee Duncan <lduncan@suse.com>
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Li Nan <linan122@huawei.com>