Re: [PATCH 2/2] target: iscsi: free cmds before session free

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On 2023-01-25 09:33, Dmitry Bogdanov wrote:
Commands from recovery entries are freed after its session has been
closed. That leads to use-after-free at command free or NPE with such
call trace:

Time2Retain timer expired for SID: 1, cleaning up iSCSI session.
BUG: kernel NULL pointer dereference, address: 0000000000000140
RIP: 0010:sbitmap_queue_clear+0x3a/0xa0
Call Trace:
  target_release_cmd_kref+0xd1/0x1f0 [target_core_mod]
  transport_generic_free_cmd+0xd1/0x180 [target_core_mod]
  iscsit_free_cmd+0x53/0xd0 [iscsi_target_mod]
  iscsit_free_connection_recovery_entries+0x29d/0x320 [iscsi_target_mod]
  iscsit_close_session+0x13a/0x140 [iscsi_target_mod]
  iscsit_check_post_dataout+0x440/0x440 [iscsi_target_mod]
  call_timer_fn+0x24/0x140

Move cleanup of recovery enrties to before session freeing.

Reported-by: Forza <forza@xxxxxxxxxxxx>
Signed-off-by: Dmitry Bogdanov <d.bogdanov@xxxxxxxxx>
---
  drivers/target/iscsi/iscsi_target.c | 6 +++---
  1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c
index f6008675dd3f..0748cbfb9631 100644
--- a/drivers/target/iscsi/iscsi_target.c
+++ b/drivers/target/iscsi/iscsi_target.c
@@ -4521,6 +4521,9 @@ int iscsit_close_session(struct iscsit_session *sess, bool can_sleep)
  	iscsit_stop_time2retain_timer(sess);
  	spin_unlock_bh(&se_tpg->session_lock);
+ if (sess->sess_ops->ErrorRecoveryLevel == 2)
+		iscsit_free_connection_recovery_entries(sess);
+
  	/*
  	 * transport_deregister_session_configfs() will clear the
  	 * struct se_node_acl->nacl_sess pointer now as a iscsi_np process context
@@ -4544,9 +4547,6 @@ int iscsit_close_session(struct iscsit_session *sess, bool can_sleep)
transport_deregister_session(sess->se_sess); - if (sess->sess_ops->ErrorRecoveryLevel == 2)
-		iscsit_free_connection_recovery_entries(sess);
-
  	iscsit_free_all_ooo_cmdsns(sess);
spin_lock_bh(&se_tpg->session_lock);

I have not had any more issues since applying the patch, which is good news :)

Will this be backported to earlier stable kernels like 5.15.x and 6.1.x

Regards,
Forza



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