| Message ID | tencent_472581BA11BB2533E79EA21B964B2A1BC408@qq.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [V2] mptcp: pm: Fix uaf in __timer_delete_sync | expand |
Hello, Thank you for this patch! On 04/09/2024 03:01, Edward Adam Davis wrote: > There are two paths to access mptcp_pm_del_add_timer, result in a race > condition: > > CPU1 CPU2 > ==== ==== > net_rx_action > napi_poll netlink_sendmsg > __napi_poll netlink_unicast > process_backlog netlink_unicast_kernel > __netif_receive_skb genl_rcv > __netif_receive_skb_one_core netlink_rcv_skb > NF_HOOK genl_rcv_msg > ip_local_deliver_finish genl_family_rcv_msg > ip_protocol_deliver_rcu genl_family_rcv_msg_doit > tcp_v4_rcv mptcp_pm_nl_flush_addrs_doit > tcp_v4_do_rcv mptcp_nl_remove_addrs_list > tcp_rcv_established mptcp_pm_remove_addrs_and_subflows > tcp_data_queue remove_anno_list_by_saddr > mptcp_incoming_options mptcp_pm_del_add_timer > mptcp_pm_del_add_timer kfree(entry) > > In remove_anno_list_by_saddr(running on CPU2), after leaving the critical > zone protected by "pm.lock", the entry will be released, which leads to the > occurrence of uaf in the mptcp_pm_del_add_timer(running on CPU1). > > Reported-and-tested-by: syzbot+f3a31fb909db9b2a5c4d@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d Please add a Fixes tag and Cc stable. And add 'net' after PATCH in the subject: [PATCH net v3] > Signed-off-by: Edward Adam Davis <eadavis@qq.com> > --- > net/mptcp/pm_netlink.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c > index 3e4ad801786f..d4cbf7dcf983 100644 > --- a/net/mptcp/pm_netlink.c > +++ b/net/mptcp/pm_netlink.c > @@ -1430,8 +1430,10 @@ static bool remove_anno_list_by_saddr(struct mptcp_sock *msk, > > entry = mptcp_pm_del_add_timer(msk, addr, false); > if (entry) { > + spin_lock_bh(&msk->pm.lock); > list_del(&entry->list); > kfree(entry); > + spin_unlock_bh(&msk->pm.lock); Mmh, I can understand it would help to reduce issues here, but I don't think that's enough: in mptcp_pm_del_add_timer(), CPU1 can get the entry from the list under the lock, then immediately after, the free can happen on CPU2, while CPU1 is trying to access entry->add_timer outside the lock, no? Something like this: CPU1 CPU2 ==== ==== entry = (...) kfree(entry) entry->add_timer What about keeping a reference to add_timer inside the lock, and calling sk_stop_timer_sync() with this reference, instead of "entry->add_timer"? I'm thinking about something like that to be applied *on top* of your patch, WDYT? https://lore.kernel.org/20240904170517.237863-2-matttbe@kernel.org Cheers, Matt
On Wed, 4 Sep 2024 22:39:10 +0200, Matthieu Baerts wrote: >On 04/09/2024 03:01, Edward Adam Davis wrote: >> There are two paths to access mptcp_pm_del_add_timer, result in a race >> condition: >> >> CPU1 CPU2 >> ==== ==== >> net_rx_action >> napi_poll netlink_sendmsg >> __napi_poll netlink_unicast >> process_backlog netlink_unicast_kernel >> __netif_receive_skb genl_rcv >> __netif_receive_skb_one_core netlink_rcv_skb >> NF_HOOK genl_rcv_msg >> ip_local_deliver_finish genl_family_rcv_msg >> ip_protocol_deliver_rcu genl_family_rcv_msg_doit >> tcp_v4_rcv mptcp_pm_nl_flush_addrs_doit >> tcp_v4_do_rcv mptcp_nl_remove_addrs_list >> tcp_rcv_established mptcp_pm_remove_addrs_and_subflows >> tcp_data_queue remove_anno_list_by_saddr >> mptcp_incoming_options mptcp_pm_del_add_timer >> mptcp_pm_del_add_timer kfree(entry) >> >> In remove_anno_list_by_saddr(running on CPU2), after leaving the critical >> zone protected by "pm.lock", the entry will be released, which leads to the >> occurrence of uaf in the mptcp_pm_del_add_timer(running on CPU1). >> >> Reported-and-tested-by: syzbot+f3a31fb909db9b2a5c4d@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d > >Please add a Fixes tag and Cc stable. > >And add 'net' after PATCH in the subject: Got it, I have added them in V3 patch. > > [PATCH net v3] > >> Signed-off-by: Edward Adam Davis <eadavis@qq.com> >> --- >> net/mptcp/pm_netlink.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c >> index 3e4ad801786f..d4cbf7dcf983 100644 >> --- a/net/mptcp/pm_netlink.c >> +++ b/net/mptcp/pm_netlink.c >> @@ -1430,8 +1430,10 @@ static bool remove_anno_list_by_saddr(struct mptcp_sock *msk, >> >> entry = mptcp_pm_del_add_timer(msk, addr, false); >> if (entry) { >> + spin_lock_bh(&msk->pm.lock); >> list_del(&entry->list); >> kfree(entry); >> + spin_unlock_bh(&msk->pm.lock); > >Mmh, I can understand it would help to reduce issues here, but I don't >think that's enough: in mptcp_pm_del_add_timer(), CPU1 can get the entry >from the list under the lock, then immediately after, the free can >happen on CPU2, while CPU1 is trying to access entry->add_timer outside >the lock, no? Something like this: > > CPU1 CPU2 > ==== ==== > entry = (...) > kfree(entry) > entry->add_timer > > >What about keeping a reference to add_timer inside the lock, and calling >sk_stop_timer_sync() with this reference, instead of "entry->add_timer"? >I'm thinking about something like that to be applied *on top* of your >patch, WDYT? I strongly agree. This can avoid accessing the entry outside the lock. I have integrated your code to my patch. BR, Edward
diff --git a/net/mptcp/pm_netlink.c b/net/mptcp/pm_netlink.c index 3e4ad801786f..d4cbf7dcf983 100644 --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -1430,8 +1430,10 @@ static bool remove_anno_list_by_saddr(struct mptcp_sock *msk, entry = mptcp_pm_del_add_timer(msk, addr, false); if (entry) { + spin_lock_bh(&msk->pm.lock); list_del(&entry->list); kfree(entry); + spin_unlock_bh(&msk->pm.lock); return true; }
There are two paths to access mptcp_pm_del_add_timer, result in a race condition: CPU1 CPU2 ==== ==== net_rx_action napi_poll netlink_sendmsg __napi_poll netlink_unicast process_backlog netlink_unicast_kernel __netif_receive_skb genl_rcv __netif_receive_skb_one_core netlink_rcv_skb NF_HOOK genl_rcv_msg ip_local_deliver_finish genl_family_rcv_msg ip_protocol_deliver_rcu genl_family_rcv_msg_doit tcp_v4_rcv mptcp_pm_nl_flush_addrs_doit tcp_v4_do_rcv mptcp_nl_remove_addrs_list tcp_rcv_established mptcp_pm_remove_addrs_and_subflows tcp_data_queue remove_anno_list_by_saddr mptcp_incoming_options mptcp_pm_del_add_timer mptcp_pm_del_add_timer kfree(entry) In remove_anno_list_by_saddr(running on CPU2), after leaving the critical zone protected by "pm.lock", the entry will be released, which leads to the occurrence of uaf in the mptcp_pm_del_add_timer(running on CPU1). Reported-and-tested-by: syzbot+f3a31fb909db9b2a5c4d@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d Signed-off-by: Edward Adam Davis <eadavis@qq.com> --- net/mptcp/pm_netlink.c | 2 ++ 1 file changed, 2 insertions(+)