diff options
| author | Xiang Mei (Microsoft) <xmei5@asu.edu> | 2026-07-22 00:29:50 +0000 |
|---|---|---|
| committer | Jakub Kicinski <kuba@kernel.org> | 2026-07-24 15:00:56 -0700 |
| commit | 072cd1f21819dedd2252e704d255de3b0cfc61a7 (patch) | |
| tree | ae90b6e602a5bddbf98a64f9d5f082b9d0cce499 | |
| parent | 9736d2efc99670054359e153a9f312ef4646ec7b (diff) | |
nexthop: take nh->lock for f6i_list walks in replace check and notify
fib6_check_nh_list() and __nexthop_replace_notify() walk nh->f6i_list
during an RTNL-serialized nexthop replace without holding nh->lock. IPv6
RTM_NEWROUTE/RTM_DELROUTE run without RTNL and mutate that list under
nh->lock (fib6_add_rt2node_nh(), fib6_purge_rt()), so both walks race a
concurrent route delete that unlinks and frees a fib6_info:
BUG: KASAN: slab-use-after-free in rt6_fill_node.isra.0 (net/ipv6/route.c:5799)
Read of size 4 at addr ffff888014607e64 by task exploit/143
rt6_fill_node.isra.0 (net/ipv6/route.c:5799)
fib6_rt_update (net/ipv6/route.c:6412)
__nexthop_replace_notify (net/ipv4/nexthop.c:2542)
rtm_new_nexthop (net/ipv4/nexthop.c:2554)
rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)
BUG: KASAN: slab-use-after-free in fib6_check_nh_list (net/ipv4/nexthop.c:1605)
Read of size 8 at addr ffff888014a7d068 by task exploit/142
fib6_check_nh_list (net/ipv4/nexthop.c:1605)
rtm_new_nexthop (net/ipv4/nexthop.c:2575)
rtnetlink_rcv_msg (net/core/rtnetlink.c:7076)
Both walks only read the entries and take no tb6_lock, so protect them
with nh->lock; fib6_rt_update() uses gfp_any(), which returns GFP_ATOMIC
under the lock.
Fixes: 081efd18326e ("ipv6: Protect nh->f6i_list with spinlock and flag.")
Reported-by: AutonomousCodeSecurity@microsoft.com
Signed-off-by: Xiang Mei (Microsoft) <xmei5@asu.edu>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Link: https://patch.msgid.link/20260722002951.2614721-1-xmei5@asu.edu
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
| -rw-r--r-- | net/ipv4/nexthop.c | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index 44fe75004cac..eb5c76ac807b 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -1597,14 +1597,21 @@ static int fib6_check_nh_list(struct nexthop *old, struct nexthop *new, struct netlink_ext_ack *extack) { struct fib6_info *f6i; + int err = 0; if (list_empty(&old->f6i_list)) return 0; + spin_lock_bh(&old->lock); list_for_each_entry(f6i, &old->f6i_list, nh_list) { - if (check_src_addr(&f6i->fib6_src.addr, extack) < 0) - return -EINVAL; + err = check_src_addr(&f6i->fib6_src.addr, extack); + if (err) + break; } + spin_unlock_bh(&old->lock); + + if (err) + return err; return fib6_check_nexthop(new, NULL, extack); } @@ -2538,8 +2545,10 @@ static void __nexthop_replace_notify(struct net *net, struct nexthop *nh, fi->nh_updated = false; } + spin_lock_bh(&nh->lock); list_for_each_entry(f6i, &nh->f6i_list, nh_list) fib6_rt_update(net, f6i, info); + spin_unlock_bh(&nh->lock); } /* send RTM_NEWROUTE with REPLACE flag set for all FIB entries |