[PATCH 5.9 040/252] sctp: change to hold/put transport for proto_unreach_timer

Greg Kroah-Hartman
2020-11-23T12:44:03Z

From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 057a10fa1f73d745c8e69aa54ab147715f5630ae ]

A call trace was found in Hangbin's Codenomicon testing with debug kernel:

[ 2615.981988] ODEBUG: free active (active state 0) object type: timer_list hint: sctp_generate_proto_unreach_event+0x0/0x3a0 [sctp]
[ 2615.995050] WARNING: CPU: 17 PID: 0 at lib/debugobjects.c:328 debug_print_object+0x199/0x2b0
[ 2616.095934] RIP: 0010:debug_print_object+0x199/0x2b0
[ 2616.191533] Call Trace:
[ 2616.194265] <IRQ>
[ 2616.202068] debug_check_no_obj_freed+0x25e/0x3f0
[ 2616.207336] slab_free_freelist_hook+0xeb/0x140
[ 2616.220971] kfree+0xd6/0x2c0
[ 2616.224293] rcu_do_batch+0x3bd/0xc70
[ 2616.243096] rcu_core+0x8b9/0xd00
[ 2616.256065] __do_softirq+0x23d/0xacd
[ 2616.260166] irq_exit+0x236/0x2a0
[ 2616.263879] smp_apic_timer_interrupt+0x18d/0x620
[ 2616.269138] apic_timer_interrupt+0xf/0x20
[ 2616.273711] </IRQ>

This is because it holds asoc when transport->proto_unreach_timer starts
and puts asoc when the timer stops, and without holding transport the
transport could be freed when the timer is still running.

So fix it by holding/putting transport instead for proto_unreach_timer
in transport, just like other timers in transport.

v1->v2:
- Also use sctp_transport_put() for the "out_unlock:" path in
sctp_generate_proto_unreach_event(), as Marcelo noticed.

Fixes: 50b5d6ad6382 ("sctp: Fix a race between ICMP protocol unreachable and connect()")
Reported-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Link: https://lore.kernel.org/r/102788809b554958b13b95d33440f5448113b8d6.1605331373.git.lucien.xin@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sctp/input.c | 4 ++--
net/sctp/sm_sideeffect.c | 4 ++--
net/sctp/transport.c | 2 +-
3 files changed, 5 insertions(+), 5 deletions(-)

--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -449,7 +449,7 @@ void sctp_icmp_proto_unreachable(struct
else {
if (!mod_timer(&t->proto_unreach_timer,
jiffies + (HZ/20)))
- sctp_association_hold(asoc);
+ sctp_transport_hold(t);
}
} else {
struct net *net = sock_net(sk);
@@ -458,7 +458,7 @@ void sctp_icmp_proto_unreachable(struct
"encountered!\n", __func__);

if (del_timer(&t->proto_unreach_timer))
- sctp_association_put(asoc);
+ sctp_transport_put(t);

sctp_do_sm(net, SCTP_EVENT_T_OTHER,
SCTP_ST_OTHER(SCTP_EVENT_ICMP_PROTO_UNREACH),
--- a/net/sctp/sm_sideeffect.c
+++ b/net/sctp/sm_sideeffect.c
@@ -419,7 +419,7 @@ void sctp_generate_proto_unreach_event(s
/* Try again later. */
if (!mod_timer(&transport->proto_unreach_timer,
jiffies + (HZ/20)))
- sctp_association_hold(asoc);
+ sctp_transport_hold(transport);
goto out_unlock;
}

@@ -435,7 +435,7 @@ void sctp_generate_proto_unreach_event(s

out_unlock:
bh_unlock_sock(sk);
- sctp_association_put(asoc);
+ sctp_transport_put(transport);
}

/* Handle the timeout of the RE-CONFIG timer. */
--- a/net/sctp/transport.c
+++ b/net/sctp/transport.c
@@ -133,7 +133,7 @@ void sctp_transport_free(struct sctp_tra

/* Delete the ICMP proto unreachable timer if it's active. */
if (del_timer(&transport->proto_unreach_timer))
- sctp_association_put(transport->asoc);
+ sctp_transport_put(transport);

sctp_transport_put(transport);
}