From: Edward Adam Davis <eadavis@xxxxxx>
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).
Keeping a reference to add_timer inside the lock, and calling
sk_stop_timer_sync() with this reference, instead of "entry->add_timer".
Move list_del(&entry->list) to mptcp_pm_del_add_timer and inside the pm lock,
do not directly access any members of the entry outside the pm lock, which
can avoid similar "entry->x" uaf.
Fixes: 00cfd77b9063 ("mptcp: retransmit ADD_ADDR when timeout")
Cc: stable@xxxxxxxxxxxxxxx
Reported-and-tested-by: syzbot+f3a31fb909db9b2a5c4d@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Signed-off-by: Edward Adam Davis <eadavis@xxxxxx>
Acked-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Link: https://patch.msgid.link/tencent_7142963A37944B4A74EF76CD66EA3C253609@xxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
(cherry picked from commit b4cd80b0338945a94972ac3ed54f8338d2da2076)
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/mptcp/pm_netlink.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
--- a/net/mptcp/pm_netlink.c
+++ b/net/mptcp/pm_netlink.c
@@ -253,15 +253,21 @@ mptcp_pm_del_add_timer(struct mptcp_sock
{
struct mptcp_pm_add_entry *entry;
struct sock *sk = (struct sock *)msk;
+ struct timer_list *add_timer = NULL;
spin_lock_bh(&msk->pm.lock);
entry = mptcp_lookup_anno_list_by_saddr(msk, addr);
- if (entry && (!check_id || entry->addr.id == addr->id))
+ if (entry && (!check_id || entry->addr.id == addr->id)) {
entry->retrans_times = ADD_ADDR_RETRANS_MAX;
+ add_timer = &entry->add_timer;
+ }
+ if (!check_id && entry)
+ list_del(&entry->list);
spin_unlock_bh(&msk->pm.lock);
- if (entry && (!check_id || entry->addr.id == addr->id))
- sk_stop_timer_sync(sk, &entry->add_timer);
+ /* no lock, because sk_stop_timer_sync() is calling del_timer_sync() */
+ if (add_timer)
+ sk_stop_timer_sync(sk, add_timer);
return entry;
}
@@ -766,7 +772,6 @@ static bool remove_anno_list_by_saddr(st
entry = mptcp_pm_del_add_timer(msk, addr, false);
if (entry) {
- list_del(&entry->list);
kfree(entry);
return true;
}
Patches currently in stable-queue which might be from matttbe@xxxxxxxxxx are
queue-5.10/mptcp-pm-fix-uaf-in-__timer_delete_sync.patch
queue-5.10/mptcp-validate-id-when-stopping-the-add_addr-retransmit-timer.patch
queue-5.10/mptcp-export-lookup_anno_list_by_saddr.patch
