[PATCH OLK-6.6 0/2] CVE-2025-39850
Ido Schimmel (2): vxlan: Fix NPD when refreshing an FDB entry with a nexthop object vxlan: Fix NPD in {arp,neigh}_reduce() when using nexthop objects drivers/net/vxlan/vxlan_core.c | 18 ++++++++++++------ drivers/net/vxlan/vxlan_private.h | 4 +--- 2 files changed, 13 insertions(+), 9 deletions(-) -- 2.34.1
From: Ido Schimmel <idosch@nvidia.com> mainline inclusion from mainline-v6.17-rc5 commit 6ead38147ebb813f08be6ea8ef547a0e4c09559a category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICYXVX CVE: CVE-2025-39850 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- VXLAN FDB entries can point to either a remote destination or an FDB nexthop group. The latter is usually used in EVPN deployments where learning is disabled. However, when learning is enabled, an incoming packet might try to refresh an FDB entry that points to an FDB nexthop group and therefore does not have a remote. Such packets should be dropped, but they are only dropped after dereferencing the non-existent remote, resulting in a NPD [1] which can be reproduced using [2]. Fix by dropping such packets earlier. Remove the misleading comment from first_remote_rcu(). [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] CPU: 13 UID: 0 PID: 361 Comm: mausezahn Not tainted 6.17.0-rc1-virtme-g9f6b606b6b37 #1 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 RIP: 0010:vxlan_snoop+0x98/0x1e0 [...] Call Trace: <TASK> vxlan_encap_bypass+0x209/0x240 encap_bypass_if_local+0xb1/0x100 vxlan_xmit_one+0x1375/0x17e0 vxlan_xmit+0x6b4/0x15f0 dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 packet_sendmsg+0x113a/0x1850 __sock_sendmsg+0x38/0x70 __sys_sendto+0x126/0x180 __x64_sys_sendto+0x24/0x30 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x4b/0x53 [2] #!/bin/bash ip address add 192.0.2.1/32 dev lo ip address add 192.0.2.2/32 dev lo ip nexthop add id 1 via 192.0.2.3 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 192.0.2.1 dstport 12345 localbypass ip link add name vx1 up type vxlan id 10020 local 192.0.2.2 dstport 54321 learning bridge fdb add 00:11:22:33:44:55 dev vx0 self static dst 192.0.2.2 port 54321 vni 10020 bridge fdb add 00:aa:bb:cc:dd:ee dev vx1 self static nhid 10 mausezahn vx0 -a 00:aa:bb:cc:dd:ee -b 00:11:22:33:44:55 -c 1 -q Fixes: 1274e1cc4226 ("vxlan: ecmp support for mac fdb entries") Reported-by: Marlin Cremers <mcremers@cloudbear.nl> Reviewed-by: Petr Machata <petrm@nvidia.com> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org> Link: https://patch.msgid.link/20250901065035.159644-2-idosch@nvidia.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Conflicts: drivers/net/vxlan/vxlan_core.c [context conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- drivers/net/vxlan/vxlan_core.c | 8 ++++---- drivers/net/vxlan/vxlan_private.h | 4 +--- 2 files changed, 5 insertions(+), 7 deletions(-) diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index 64db3e98a1b6..4f01e6d1bb95 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -1460,6 +1460,10 @@ static bool vxlan_snoop(struct net_device *dev, if (likely(f)) { struct vxlan_rdst *rdst = first_remote_rcu(f); + /* Don't override an fdb with nexthop with a learnt entry */ + if (rcu_access_pointer(f->nh)) + return true; + if (likely(vxlan_addr_equal(&rdst->remote_ip, src_ip) && rdst->remote_ifindex == ifindex)) return false; @@ -1468,10 +1472,6 @@ static bool vxlan_snoop(struct net_device *dev, if (f->state & (NUD_PERMANENT | NUD_NOARP)) return true; - /* Don't override an fdb with nexthop with a learnt entry */ - if (rcu_access_pointer(f->nh)) - return true; - if (net_ratelimit()) netdev_info(dev, "%pM migrated from %pIS to %pIS\n", diff --git a/drivers/net/vxlan/vxlan_private.h b/drivers/net/vxlan/vxlan_private.h index 85b6d0c347e3..8444b5d1ca60 100644 --- a/drivers/net/vxlan/vxlan_private.h +++ b/drivers/net/vxlan/vxlan_private.h @@ -56,9 +56,7 @@ static inline struct hlist_head *vs_head(struct net *net, __be16 port) return &vn->sock_list[hash_32(ntohs(port), PORT_HASH_BITS)]; } -/* First remote destination for a forwarding entry. - * Guaranteed to be non-NULL because remotes are never deleted. - */ +/* First remote destination for a forwarding entry. */ static inline struct vxlan_rdst *first_remote_rcu(struct vxlan_fdb *fdb) { if (rcu_access_pointer(fdb->nh)) -- 2.34.1
From: Ido Schimmel <idosch@nvidia.com> mainline inclusion from mainline-v6.17-rc5 commit 1f5d2fd1ca04a23c18b1bde9a43ce2fa2ffa1bce category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/ICYXVX CVE: CVE-2025-39850 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- When the "proxy" option is enabled on a VXLAN device, the device will suppress ARP requests and IPv6 Neighbor Solicitation messages if it is able to reply on behalf of the remote host. That is, if a matching and valid neighbor entry is configured on the VXLAN device whose MAC address is not behind the "any" remote (0.0.0.0 / ::). The code currently assumes that the FDB entry for the neighbor's MAC address points to a valid remote destination, but this is incorrect if the entry is associated with an FDB nexthop group. This can result in a NPD [1][3] which can be reproduced using [2][4]. Fix by checking that the remote destination exists before dereferencing it. [1] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] CPU: 4 UID: 0 PID: 365 Comm: arping Not tainted 6.17.0-rc2-virtme-g2a89cb21162c #2 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.17.0-4.fc41 04/01/2014 RIP: 0010:vxlan_xmit+0xb58/0x15f0 [...] Call Trace: <TASK> dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 packet_sendmsg+0x113a/0x1850 __sock_sendmsg+0x38/0x70 __sys_sendto+0x126/0x180 __x64_sys_sendto+0x24/0x30 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x4b/0x53 [2] #!/bin/bash ip address add 192.0.2.1/32 dev lo ip nexthop add id 1 via 192.0.2.2 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 192.0.2.1 dstport 4789 proxy ip neigh add 192.0.2.3 lladdr 00:11:22:33:44:55 nud perm dev vx0 bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10 arping -b -c 1 -s 192.0.2.1 -I vx0 192.0.2.3 [3] BUG: kernel NULL pointer dereference, address: 0000000000000000 [...] CPU: 13 UID: 0 PID: 372 Comm: ndisc6 Not tainted 6.17.0-rc2-virtmne-g6ee90cb26014 #3 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1v996), BIOS 1.17.0-4.fc41 04/01/2x014 RIP: 0010:vxlan_xmit+0x803/0x1600 [...] Call Trace: <TASK> dev_hard_start_xmit+0x5d/0x1c0 __dev_queue_xmit+0x246/0xfd0 ip6_finish_output2+0x210/0x6c0 ip6_finish_output+0x1af/0x2b0 ip6_mr_output+0x92/0x3e0 ip6_send_skb+0x30/0x90 rawv6_sendmsg+0xe6e/0x12e0 __sock_sendmsg+0x38/0x70 __sys_sendto+0x126/0x180 __x64_sys_sendto+0x24/0x30 do_syscall_64+0xa4/0x260 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x7f383422ec77 [4] #!/bin/bash ip address add 2001:db8:1::1/128 dev lo ip nexthop add id 1 via 2001:db8:1::1 fdb ip nexthop add id 10 group 1 fdb ip link add name vx0 up type vxlan id 10010 local 2001:db8:1::1 dstport 4789 proxy ip neigh add 2001:db8:1::3 lladdr 00:11:22:33:44:55 nud perm dev vx0 bridge fdb add 00:11:22:33:44:55 dev vx0 self static nhid 10 ndisc6 -r 1 -s 2001:db8:1::1 -w 1 2001:db8:1::3 vx0 Fixes: 1274e1cc4226 ("vxlan: ecmp support for mac fdb entries") Reviewed-by: Petr Machata <petrm@nvidia.com> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org> Link: https://patch.msgid.link/20250901065035.159644-3-idosch@nvidia.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Conflicts: drivers/net/vxlan/vxlan_core.c [context conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- drivers/net/vxlan/vxlan_core.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c index 4f01e6d1bb95..797357ae0591 100644 --- a/drivers/net/vxlan/vxlan_core.c +++ b/drivers/net/vxlan/vxlan_core.c @@ -1883,6 +1883,7 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni) n = neigh_lookup(&arp_tbl, &tip, dev); if (n) { + struct vxlan_rdst *rdst = NULL; struct vxlan_fdb *f; struct sk_buff *reply; @@ -1892,7 +1893,9 @@ static int arp_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni) } f = vxlan_find_mac(vxlan, n->ha, vni); - if (f && vxlan_addr_any(&(first_remote_rcu(f)->remote_ip))) { + if (f) + rdst = first_remote_rcu(f); + if (rdst && vxlan_addr_any(&rdst->remote_ip)) { /* bridge-local neighbor */ neigh_release(n); goto out; @@ -2047,6 +2050,7 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni) n = neigh_lookup(ipv6_stub->nd_tbl, &msg->target, dev); if (n) { + struct vxlan_rdst *rdst = NULL; struct vxlan_fdb *f; struct sk_buff *reply; @@ -2056,7 +2060,9 @@ static int neigh_reduce(struct net_device *dev, struct sk_buff *skb, __be32 vni) } f = vxlan_find_mac(vxlan, n->ha, vni); - if (f && vxlan_addr_any(&(first_remote_rcu(f)->remote_ip))) { + if (f) + rdst = first_remote_rcu(f); + if (rdst && vxlan_addr_any(&rdst->remote_ip)) { /* bridge-local neighbor */ neigh_release(n); goto out; -- 2.34.1
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