diff options
| author | Eric Dumazet <edumazet@google.com> | 2026-01-24 13:59:18 +0300 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-01-27 06:32:59 +0300 |
| commit | e2a9eeb69f7d4ca4cf4c70463af77664fdb6ab1d (patch) | |
| tree | bdb9ffb74d3847f751e3fbe24b4523cfedbf6372 | |
| parent | 8d7ba71e46216b8657a82ca2ec118bc93812a4d0 (diff) | |
| download | linux-e2a9eeb69f7d4ca4cf4c70463af77664fdb6ab1d.tar.xz | |
mptcp: fix race in mptcp_pm_nl_flush_addrs_doit()
syzbot and Eulgyu Kim reported crashes in mptcp_pm_nl_get_local_id()
and/or mptcp_pm_nl_is_backup()
Root cause is list_splice_init() in mptcp_pm_nl_flush_addrs_doit()
which is not RCU ready.
list_splice_init_rcu() can not be called here while holding pernet->lock
spinlock.
Many thanks to Eulgyu Kim for providing a repro and testing our patches.
Fixes: 141694df6573 ("mptcp: remove address when netlink flushes addrs")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: syzbot+5498a510ff9de39d37da@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/6970a46d.a00a0220.3ad28e.5cf0.GAE@google.com/T/
Reported-by: Eulgyu Kim <eulgyukim@snu.ac.kr>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/611
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20260124-net-mptcp-race_nl_flush_addrs-v3-1-b2dc1b613e9d@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/mptcp/pm_kernel.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c index 57570a44e418..b26675054b0d 100644 --- a/net/mptcp/pm_kernel.c +++ b/net/mptcp/pm_kernel.c @@ -1294,16 +1294,26 @@ static void __reset_counters(struct pm_nl_pernet *pernet) int mptcp_pm_nl_flush_addrs_doit(struct sk_buff *skb, struct genl_info *info) { struct pm_nl_pernet *pernet = genl_info_pm_nl(info); - LIST_HEAD(free_list); + struct list_head free_list; spin_lock_bh(&pernet->lock); - list_splice_init(&pernet->endp_list, &free_list); + free_list = pernet->endp_list; + INIT_LIST_HEAD_RCU(&pernet->endp_list); __reset_counters(pernet); pernet->next_id = 1; bitmap_zero(pernet->id_bitmap, MPTCP_PM_MAX_ADDR_ID + 1); spin_unlock_bh(&pernet->lock); - mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); + + if (free_list.next == &pernet->endp_list) + return 0; + synchronize_rcu(); + + /* Adjust the pointers to free_list instead of pernet->endp_list */ + free_list.prev->next = &free_list; + free_list.next->prev = &free_list; + + mptcp_nl_flush_addrs_list(sock_net(skb->sk), &free_list); __flush_addrs(&free_list); return 0; } |