On Mon, 2017-07-31 at 14:48 -0700, Justin Maggard wrote:
> On Sun, Jul 30, 2017 at 5:15 PM, Nicholas A. Bellinger
> <nab@xxxxxxxxxxxxxxx> wrote:
> > On Thu, 2017-07-27 at 13:56 -0700, Justin Maggard wrote:
> >> I ran across a GPF after disabling demo-mode on an iSCSI target. The
> >> backtrace pointed to target_put_nacl(), which was called from
> >> transport_free_session().
> >
> > Can we see actual stack trace, and kernel version please..?
> >
>
> Sure.
<SNIP>
> Thanks a lot, that clears up my misunderstanding. I should have read
> the kref documentation carefully first.
>
> So it looks like what's *really* happening is,
> transport_free_session() does a list_del(acl_list). At least in my
> case, this empties the list. Then, target_put_nacl() calls
> target_complete_nacl(), which also does a list_del(acl_list) and
> crashes.
>
Ugh. I seem to recall the initial version of this patch was using
list_del_init(), but review feedback listed in commit 01d4d6735589
shows that it was dropped as unnecessary:
(Drop unnecessary list_del_init usage - HCH)
Note the scenario in question is specific to generate_node_acls = 1 +
cache_dynamic_acls = 0.
Here's the patch I'm applying to target-pending/master, with a CC' to
v4.1.y stable.
Please verify on your end.
Thank you.
>From 73f6806a8124357ca00fcadaa9d58f617e44947e Mon Sep 17 00:00:00 2001
From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Sun, 6 Aug 2017 16:10:03 -0700
Subject: [PATCH] target: Fix node_acl demo-mode + uncached dynamic shutdown
regression
This patch fixes a generate_node_acls = 1 + cache_dynamic_acls = 0
regression, that was introduced by
commit 01d4d673558985d9a118e1e05026633c3e2ade9b
Author: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
Date: Wed Dec 7 12:55:54 2016 -0800
which originally had the proper list_del_init() usage, but was
dropped during list review as it was thought unnecessary by HCH.
However, list_del_init() usage is required during the special
generate_node_acls = 1 + cache_dynamic_acls = 0 case when
transport_free_session() does a list_del(&se_nacl->acl_list),
followed by target_complete_nacl() doing the same thing.
This was manifesting as a general protection fault as reported
by Justin:
kernel: general protection fault: 0000 [#1] SMP
kernel: Modules linked in:
kernel: CPU: 0 PID: 11047 Comm: iscsi_ttx Not tainted 4.13.0-rc2.x86_64.1+ #20
kernel: Hardware name: Intel Corporation S5500BC/S5500BC, BIOS S5500.86B.01.00.0064.050520141428 05/05/2014
kernel: task: ffff88026939e800 task.stack: ffffc90007884000
kernel: RIP: 0010:target_put_nacl+0x49/0xb0
kernel: RSP: 0018:ffffc90007887d70 EFLAGS: 00010246
kernel: RAX: dead000000000200 RBX: ffff8802556ca000 RCX: 0000000000000000
kernel: RDX: dead000000000100 RSI: 0000000000000246 RDI: ffff8802556ce028
kernel: RBP: ffffc90007887d88 R08: 0000000000000001 R09: 0000000000000000
kernel: R10: ffffc90007887df8 R11: ffffea0009986900 R12: ffff8802556ce020
kernel: R13: ffff8802556ce028 R14: ffff8802556ce028 R15: ffffffff88d85540
kernel: FS: 0000000000000000(0000) GS:ffff88027fc00000(0000) knlGS:0000000000000000
kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
kernel: CR2: 00007fffe36f5f94 CR3: 0000000009209000 CR4: 00000000003406f0
kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
kernel: Call Trace:
kernel: transport_free_session+0x67/0x140
kernel: transport_deregister_session+0x7a/0xc0
kernel: iscsit_close_session+0x92/0x210
kernel: iscsit_close_connection+0x5f9/0x840
kernel: iscsit_take_action_for_connection_exit+0xfe/0x110
kernel: iscsi_target_tx_thread+0x140/0x1e0
kernel: ? wait_woken+0x90/0x90
kernel: kthread+0x124/0x160
kernel: ? iscsit_thread_get_cpumask+0x90/0x90
kernel: ? kthread_create_on_node+0x40/0x40
kernel: ret_from_fork+0x22/0x30
kernel: Code: 00 48 89 fb 4c 8b a7 48 01 00 00 74 68 4d 8d 6c 24 08 4c
89 ef e8 e8 28 43 00 48 8b 93 20 04 00 00 48 8b 83 28 04 00 00 4c 89
ef <48> 89 42 08 48 89 10 48 b8 00 01 00 00 00 00 ad de 48 89 83 20
kernel: RIP: target_put_nacl+0x49/0xb0 RSP: ffffc90007887d70
kernel: ---[ end trace f12821adbfd46fed ]---
To address this, go ahead and use proper list_del_list() for all
cases of se_nacl->acl_list deletion.
Reported-by: Justin Maggard <jmaggard01@xxxxxxxxx>
Cc: Justin Maggard <jmaggard01@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # 4.1+
Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
---
drivers/target/target_core_tpg.c | 4 ++--
drivers/target/target_core_transport.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index 3691373..02e8a5d 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -364,7 +364,7 @@ void core_tpg_del_initiator_node_acl(struct se_node_acl *acl)
mutex_lock(&tpg->acl_node_mutex);
if (acl->dynamic_node_acl)
acl->dynamic_node_acl = 0;
- list_del(&acl->acl_list);
+ list_del_init(&acl->acl_list);
mutex_unlock(&tpg->acl_node_mutex);
target_shutdown_sessions(acl);
@@ -548,7 +548,7 @@ int core_tpg_deregister(struct se_portal_group *se_tpg)
* in transport_deregister_session().
*/
list_for_each_entry_safe(nacl, nacl_tmp, &node_list, acl_list) {
- list_del(&nacl->acl_list);
+ list_del_init(&nacl->acl_list);
core_tpg_wait_for_nacl_pr_ref(nacl);
core_free_device_list_for_node(nacl, se_tpg);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index 97fed9a..836d552 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -466,7 +466,7 @@ static void target_complete_nacl(struct kref *kref)
}
mutex_lock(&se_tpg->acl_node_mutex);
- list_del(&nacl->acl_list);
+ list_del_init(&nacl->acl_list);
mutex_unlock(&se_tpg->acl_node_mutex);
core_tpg_wait_for_nacl_pr_ref(nacl);
@@ -538,7 +538,7 @@ void transport_free_session(struct se_session *se_sess)
spin_unlock_irqrestore(&se_nacl->nacl_sess_lock, flags);
if (se_nacl->dynamic_stop)
- list_del(&se_nacl->acl_list);
+ list_del_init(&se_nacl->acl_list);
}
mutex_unlock(&se_tpg->acl_node_mutex);
--
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