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mptcp: pm: Fix uaf in __timer_delete_sync
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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: [email protected]
Closes: https://syzkaller.appspot.com/bug?extid=f3a31fb909db9b2a5c4d
Signed-off-by: Edward Adam Davis <[email protected]>
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Edward-AD authored and intel-lab-lkp committed Sep 4, 2024
1 parent 680eef4 commit 28192de
Showing 1 changed file with 2 additions and 0 deletions.
2 changes: 2 additions & 0 deletions net/mptcp/pm_netlink.c
Original file line number Diff line number Diff line change
Expand Up @@ -1452,8 +1452,10 @@ 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;
}

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