From 61fe578156c4c9bad13e83efdf4a1546c1bab3cd Mon Sep 17 00:00:00 2001 From: Artem Savkov Date: Mon, 26 Jul 2021 12:27:34 +0200 Subject: [PATCH] can: bcm: delay release of struct bcm_op after synchronize_rcu() Kernels: 4.18.0-305.el8 4.18.0-305.3.1.el8_4 4.18.0-305.7.1.el8_4 4.18.0-305.10.2.el8_4 Changes since last build: arches: x86_64 ppc64le bcm.o: changed function: bcm_release bcm.o: changed function: bcm_sendmsg --------------------------- Kernels: 4.18.0-305.el8 4.18.0-305.3.1.el8_4 4.18.0-305.7.1.el8_4 4.18.0-305.10.2.el8_4 Modifications: none commit 14c1d51567d0ef31ef900f6d1641615924fdb239 Author: Hangbin Liu Date: Mon Jun 28 14:50:49 2021 +0800 can: bcm: delay release of struct bcm_op after synchronize_rcu() Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1975058 Y-Commit: fc088504ba6bee277b7bdc93ab0988b648bb8b81 Upstream Status: net.git commit d5f9023fa61e CVE: CVE-2021-3609 O-Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1975059 commit d5f9023fa61ee8b94f37a93f08e94b136cf1e463 Author: Thadeu Lima de Souza Cascardo Date: Sat Jun 19 13:18:13 2021 -0300 can: bcm: delay release of struct bcm_op after synchronize_rcu() can_rx_register() callbacks may be called concurrently to the call to can_rx_unregister(). The callbacks and callback data, though, are protected by RCU and the struct sock reference count. So the callback data is really attached to the life of sk, meaning that it should be released on sk_destruct. However, bcm_remove_op() calls tasklet_kill(), and RCU callbacks may be called under RCU softirq, so that cannot be used on kernels before the introduction of HRTIMER_MODE_SOFT. However, bcm_rx_handler() is called under RCU protection, so after calling can_rx_unregister(), we may call synchronize_rcu() in order to wait for any RCU read-side critical sections to finish. That is, bcm_rx_handler() won't be called anymore for those ops. So, we only free them, after we do that synchronize_rcu(). Fixes: ffd980f976e7 ("[CAN]: Add broadcast manager (bcm) protocol") Link: https://lore.kernel.org/r/20210619161813.2098382-1-cascardo@canonical.com Cc: linux-stable Reported-by: syzbot+0f7e7e5e2f4f40fa89c0@syzkaller.appspotmail.com Reported-by: Norbert Slusarek Signed-off-by: Thadeu Lima de Souza Cascardo Acked-by: Oliver Hartkopp Signed-off-by: Marc Kleine-Budde Signed-off-by: Hangbin Liu Signed-off-by: Artem Savkov Acked-by: Joe Lawrence --- net/can/bcm.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/net/can/bcm.c b/net/can/bcm.c index 0af8f0db892a3..4ee2fd682afaa 100644 --- a/net/can/bcm.c +++ b/net/can/bcm.c @@ -802,6 +802,7 @@ static int bcm_delete_rx_op(struct list_head *ops, struct bcm_msg_head *mh, bcm_rx_handler, op); list_del(&op->list); + synchronize_rcu(); bcm_remove_op(op); return 1; /* done */ } @@ -1527,9 +1528,13 @@ static int bcm_release(struct socket *sock) REGMASK(op->can_id), bcm_rx_handler, op); - bcm_remove_op(op); } + synchronize_rcu(); + + list_for_each_entry_safe(op, next, &bo->rx_ops, list) + bcm_remove_op(op); + #if IS_ENABLED(CONFIG_PROC_FS) /* remove procfs entry */ if (net->can.bcmproc_dir && bo->bcm_proc_read) -- 2.26.3