This is a note to let you know that I've just added the patch titled sctp: change to hold/put transport for proto_unreach_timer to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: sctp-change-to-hold-put-transport-for-proto_unreach_timer.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Sun Nov 22 12:23:07 PM CET 2020 From: Xin Long <lucien.xin@xxxxxxxxx> Date: Sat, 14 Nov 2020 13:22:53 +0800 Subject: sctp: change to hold/put transport for proto_unreach_timer From: Xin Long <lucien.xin@xxxxxxxxx> [ 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@xxxxxxxxx> Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx> Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx> Link: https://lore.kernel.org/r/102788809b554958b13b95d33440f5448113b8d6.1605331373.git.lucien.xin@xxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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 @@ -448,7 +448,7 @@ 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); @@ -457,7 +457,7 @@ 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 @@ -416,7 +416,7 @@ void sctp_generate_proto_unreach_event(u /* Try again later. */ if (!mod_timer(&transport->proto_unreach_timer, jiffies + (HZ/20))) - sctp_association_hold(asoc); + sctp_transport_hold(transport); goto out_unlock; } @@ -432,7 +432,7 @@ void sctp_generate_proto_unreach_event(u out_unlock: bh_unlock_sock(sk); - sctp_association_put(asoc); + sctp_transport_put(transport); } --- a/net/sctp/transport.c +++ b/net/sctp/transport.c @@ -148,7 +148,7 @@ 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); } Patches currently in stable-queue which might be from lucien.xin@xxxxxxxxx are queue-4.4/sctp-change-to-hold-put-transport-for-proto_unreach_timer.patch