From: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx> commit 48e50dcbcbaaf713d82bf2da5c16aeced94ad07d upstream. select_local_address() and select_signal_address() both select an endpoint entry from the list inside an RCU protected section, but return a reference to it, to be read later on. If the entry is dereferenced after the RCU unlock, reading info could cause a Use-after-Free. A simple solution is to copy the required info while inside the RCU protected section to avoid any risk of UaF later. The address ID might need to be modified later to handle the ID0 case later, so a copy seems OK to deal with. Reported-by: Paolo Abeni <pabeni@xxxxxxxxxx> Closes: https://lore.kernel.org/45cd30d3-7710-491c-ae4d-a1368c00beb1@xxxxxxxxxx Fixes: 01cacb00b35c ("mptcp: add netlink-based PM") Cc: stable@xxxxxxxxxxxxxxx Reviewed-by: Mat Martineau <martineau@xxxxxxxxxx> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@xxxxxxxxxx> Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-14-38035d40de5b@xxxxxxxxxx Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- net/mptcp/pm_netlink.c | 64 ++++++++++++++++++++++++++----------------------- 1 file changed, 34 insertions(+), 30 deletions(-) --- a/net/mptcp/pm_netlink.c +++ b/net/mptcp/pm_netlink.c @@ -148,11 +148,13 @@ static bool lookup_subflow_by_daddr(cons return false; } -static struct mptcp_pm_addr_entry * +static bool select_local_address(const struct pm_nl_pernet *pernet, - const struct mptcp_sock *msk) + const struct mptcp_sock *msk, + struct mptcp_pm_addr_entry *new_entry) { - struct mptcp_pm_addr_entry *entry, *ret = NULL; + struct mptcp_pm_addr_entry *entry; + bool found = false; msk_owned_by_me(msk); @@ -164,17 +166,21 @@ select_local_address(const struct pm_nl_ if (!test_bit(entry->addr.id, msk->pm.id_avail_bitmap)) continue; - ret = entry; + *new_entry = *entry; + found = true; break; } rcu_read_unlock(); - return ret; + + return found; } -static struct mptcp_pm_addr_entry * -select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk) +static bool +select_signal_address(struct pm_nl_pernet *pernet, const struct mptcp_sock *msk, + struct mptcp_pm_addr_entry *new_entry) { - struct mptcp_pm_addr_entry *entry, *ret = NULL; + struct mptcp_pm_addr_entry *entry; + bool found = false; rcu_read_lock(); /* do not keep any additional per socket state, just signal @@ -189,11 +195,13 @@ select_signal_address(struct pm_nl_perne if (!(entry->flags & MPTCP_PM_ADDR_FLAG_SIGNAL)) continue; - ret = entry; + *new_entry = *entry; + found = true; break; } rcu_read_unlock(); - return ret; + + return found; } unsigned int mptcp_pm_get_add_addr_signal_max(const struct mptcp_sock *msk) @@ -520,9 +528,10 @@ __lookup_addr(struct pm_nl_pernet *perne static void mptcp_pm_create_subflow_or_signal_addr(struct mptcp_sock *msk) { - struct mptcp_pm_addr_entry *local, *signal_and_subflow = NULL; struct sock *sk = (struct sock *)msk; + struct mptcp_pm_addr_entry local; unsigned int add_addr_signal_max; + bool signal_and_subflow = false; unsigned int local_addr_max; struct pm_nl_pernet *pernet; unsigned int subflows_max; @@ -573,23 +582,22 @@ static void mptcp_pm_create_subflow_or_s if (msk->pm.addr_signal & BIT(MPTCP_ADD_ADDR_SIGNAL)) return; - local = select_signal_address(pernet, msk); - if (!local) + if (!select_signal_address(pernet, msk, &local)) goto subflow; /* If the alloc fails, we are on memory pressure, not worth * continuing, and trying to create subflows. */ - if (!mptcp_pm_alloc_anno_list(msk, &local->addr)) + if (!mptcp_pm_alloc_anno_list(msk, &local.addr)) return; - __clear_bit(local->addr.id, msk->pm.id_avail_bitmap); + __clear_bit(local.addr.id, msk->pm.id_avail_bitmap); msk->pm.add_addr_signaled++; - mptcp_pm_announce_addr(msk, &local->addr, false); + mptcp_pm_announce_addr(msk, &local.addr, false); mptcp_pm_nl_addr_send_ack(msk); - if (local->flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) - signal_and_subflow = local; + if (local.flags & MPTCP_PM_ADDR_FLAG_SUBFLOW) + signal_and_subflow = true; } subflow: @@ -600,26 +608,22 @@ subflow: bool fullmesh; int i, nr; - if (signal_and_subflow) { - local = signal_and_subflow; - signal_and_subflow = NULL; - } else { - local = select_local_address(pernet, msk); - if (!local) - break; - } + if (signal_and_subflow) + signal_and_subflow = false; + else if (!select_local_address(pernet, msk, &local)) + break; - fullmesh = !!(local->flags & MPTCP_PM_ADDR_FLAG_FULLMESH); + fullmesh = !!(local.flags & MPTCP_PM_ADDR_FLAG_FULLMESH); msk->pm.local_addr_used++; - __clear_bit(local->addr.id, msk->pm.id_avail_bitmap); - nr = fill_remote_addresses_vec(msk, &local->addr, fullmesh, addrs); + __clear_bit(local.addr.id, msk->pm.id_avail_bitmap); + nr = fill_remote_addresses_vec(msk, &local.addr, fullmesh, addrs); if (nr == 0) continue; spin_unlock_bh(&msk->pm.lock); for (i = 0; i < nr; i++) - __mptcp_subflow_connect(sk, &local->addr, &addrs[i]); + __mptcp_subflow_connect(sk, &local.addr, &addrs[i]); spin_lock_bh(&msk->pm.lock); } mptcp_pm_nl_check_work_pending(msk); Patches currently in stable-queue which might be from matttbe@xxxxxxxxxx are queue-6.6/mptcp-pm-avoid-possible-uaf-when-selecting-endp.patch queue-6.6/mptcp-pm-only-decrement-add_addr_accepted-for-mpj-req.patch queue-6.6/mptcp-pm-only-in-kernel-cannot-have-entries-with-id-0.patch queue-6.6/mptcp-pm-fullmesh-select-the-right-id-later.patch queue-6.6/selftests-net-lib-kill-pids-before-del-netns.patch queue-6.6/mptcp-pm-re-using-id-of-unused-flushed-subflows.patch queue-6.6/selftests-mptcp-join-validate-fullmesh-endp-on-1st-sf.patch queue-6.6/mptcp-pm-only-mark-subflow-endp-as-available.patch queue-6.6/selftests-net-lib-ignore-possible-errors.patch queue-6.6/selftests-mptcp-join-check-re-using-id-of-closed-subflow.patch queue-6.6/mptcp-pm-re-using-id-of-unused-removed-add_addr.patch queue-6.6/mptcp-pm-check-add_addr_accept_max-before-accepting-new-add_addr.patch queue-6.6/mptcp-pm-re-using-id-of-unused-removed-subflows.patch queue-6.6/mptcp-correct-mptcp_subflow_attr_ssn_offset-reserved.patch queue-6.6/mptcp-pm-remove-mptcp_pm_remove_subflow.patch
