linux-stable.git/net/netfilter/nfnetlink_queue.c, branch v7.2 Linux kernel stable tree netfilter: handle unreadable frags 2026-07-08T13:33:44+00:00 Florian Westphal fw@strlen.de 2026-07-05T13:29:13+00:00 da5b58478a9c1b85608c9e40a3b8432d071b409e sashiko reports: When an skb with unreadable fragments (such as from devmem TCP, where skb_frags_readable(skb) returns false) is processed by the u32 module, skb_copy_bits() will safely return a negative error code [..] xt_u32: bail out with hotdrop in this case. gather_frags: return -1, just as if we had no fragment header. nfnetlink_queue: restrict to the linear part. nfnetlink_log: restrict to the linear part. v2: - skb_zerocopy helpers don't copy readable flag, i.e. nfnetlink_queue is broken too xt_u32 shouldn't return true if hotdrop was set. Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags") Cc: stable@vger.kernel.org Acked-by: Mina Almasry <almasrymina@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> 
sashiko reports:
 When an skb with unreadable fragments (such as from devmem TCP, where
 skb_frags_readable(skb) returns false) is processed by the u32 module,
 skb_copy_bits() will safely return a negative error code [..]

xt_u32: bail out with hotdrop in this case.
gather_frags: return -1, just as if we had no fragment header.
nfnetlink_queue: restrict to the linear part.
nfnetlink_log: restrict to the linear part.

v2:
 - skb_zerocopy helpers don't copy readable flag, i.e. nfnetlink_queue
 is broken too
 xt_u32 shouldn't return true if hotdrop was set.

Fixes: 65249feb6b3d ("net: add support for skbs with unreadable frags")
Cc: stable@vger.kernel.org
Acked-by: Mina Almasry <almasrymina@google.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
netfilter: nfnetlink_queue: restrict writes to network header 2026-06-30T04:45:45+00:00 Florian Westphal fw@strlen.de 2026-06-09T11:51:53+00:00 54f34607d184c1cc056c59a5b3d86d96dd6a515c nfnetlink_queue doesn't allow selective replacements of some part of the payload, only complete replacement. If the new data is shorter, skb is trimmed, otherwise expanded. Add minimal validation of the new ip/ipv6 header. Check total len matches skb length. Disallow ip option modifications. IPv6 extension headers are also disabled. IP options and exthdrs could be allowed later after validation pass or ip option recompile. Transport header is not checked. Bridge modifications are rejected. Given userspace doesn't even receive L2 headers, use is limited and I don't think there are any users of bridge nfnetlink_queue, let alone users that modifiy payload. Arp isn't supported at all. Signed-off-by: Florian Westphal <fw@strlen.de> 
nfnetlink_queue doesn't allow selective replacements of some part of the
payload, only complete replacement.
If the new data is shorter, skb is trimmed, otherwise expanded.

Add minimal validation of the new ip/ipv6 header.  Check total len
matches skb length.  Disallow ip option modifications.

IPv6 extension headers are also disabled.
IP options and exthdrs could be allowed later after validation pass or
ip option recompile.

Transport header is not checked.

Bridge modifications are rejected.  Given userspace doesn't even receive
L2 headers, use is limited and I don't think there are any users of
bridge nfnetlink_queue, let alone users that modifiy payload.

Arp isn't supported at all.

Signed-off-by: Florian Westphal <fw@strlen.de>
netfilter: nf_queue: pin bridge device while NFQUEUE holds fake dst 2026-06-19T10:19:58+00:00 Haoze Xie royenheart@gmail.com 2026-06-08T05:43:44+00:00 c9c9b37f8c5505224e8d206184df3bb668ee00cf The br_netfilter fake rtable is embedded in struct net_bridge and is attached to bridged packets with skb_dst_set_noref(). If such a packet is queued to NFQUEUE, __nf_queue() upgrades that fake dst with skb_dst_force(). At that point the queued skb can hold a real dst reference after bridge teardown has started. The problem is not that every bridged packet needs its own dst reference. The problem is that NFQUEUE can keep the bridge private fake dst alive after unregister begins. Fix this by keeping the bridge fake dst model unchanged and pinning the bridge master device only while the packet sits in NFQUEUE. Record the bridge device in nf_queue_entry when the queued skb carries a bridge fake dst, take a device reference for the queue lifetime, and drop it when the queue entry is freed. Also make sure queued entries are reaped when that bridge device goes down, and drop the redundant nf_bridge_info_exists() test from the fake dst detection. This keeps netdev_priv(br->dev) alive until verdict completion, so the embedded fake rtable and its metrics backing storage cannot be freed out from under dst_release(). It also avoids the constant refcount bump and avoids using ipv4-specific dst helpers for IPv6 bridge traffic. Fixes: 34666d467cbf ("netfilter: bridge: move br_netfilter out of the core") Cc: stable@kernel.org Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Yifan Wu <yifanwucs@gmail.com> Reported-by: Juefei Pu <tomapufckgml@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Signed-off-by: Haoze Xie <royenheart@gmail.com> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> 
The br_netfilter fake rtable is embedded in struct net_bridge and is
attached to bridged packets with skb_dst_set_noref(). If such a packet is
queued to NFQUEUE, __nf_queue() upgrades that fake dst with
skb_dst_force().

At that point the queued skb can hold a real dst reference after bridge
teardown has started. The problem is not that every bridged packet needs
its own dst reference. The problem is that NFQUEUE can keep the bridge
private fake dst alive after unregister begins.

Fix this by keeping the bridge fake dst model unchanged and pinning the
bridge master device only while the packet sits in NFQUEUE. Record the
bridge device in nf_queue_entry when the queued skb carries a bridge fake
dst, take a device reference for the queue lifetime, and drop it when the
queue entry is freed.

Also make sure queued entries are reaped when that bridge device goes
down, and drop the redundant nf_bridge_info_exists() test from the fake
dst detection.

This keeps netdev_priv(br->dev) alive until verdict completion, so the
embedded fake rtable and its metrics backing storage cannot be freed out
from under dst_release(). It also avoids the constant refcount bump and
avoids using ipv4-specific dst helpers for IPv6 bridge traffic.

Fixes: 34666d467cbf ("netfilter: bridge: move br_netfilter out of the core")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Haoze Xie <royenheart@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
netfilter: revalidate bridge ports 2026-06-10T15:58:20+00:00 Florian Westphal fw@strlen.de 2026-06-02T15:04:25+00:00 ccb9fd4b87538ccf19ccff78ee26700526d94867 ebt_redirect_tg() dereferences br_port_get_rcu() return without a NULL check, causing a kernel panic when the bridge port has been removed between the original hook invocation and an NFQUEUE reinject. A mere NULL check isn't sufficient, however. As sashiko review points out userspace can not only remove the port from the bridge, it could also place the device in a different virtual device, e.g. macvlan. If this happens, we must drop the packet, there is no way for us to reinject it into the bridge path. Switch to _upper API, we don't need the bridge port structure. Also, this fix keeps another bug intact: Both nfnetlink_log and nfnetlink_queue use CONFIG_BRIDGE_NETFILTER too aggressive, which prevents certain logging features when queueing in bridge family: NETFILTER_FAMILY_BRIDGE can be enabled while the old CONFIG_BRIDGE_NETFILTER cruft is off. Fixes tag is a common ancestor, this was always broken. Fixes: f350a0a87374 ("bridge: use rx_handler_data pointer to store net_bridge_port pointer") Reported-by: Ji'an Zhou <eilaimemedsnaimel@gmail.com> Assisted-by: Claude:claude-sonnet-4-6 Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> 
ebt_redirect_tg() dereferences br_port_get_rcu() return without a
NULL check, causing a kernel panic when the bridge port has been
removed between the original hook invocation and an NFQUEUE
reinject.

A mere NULL check isn't sufficient, however.  As sashiko review
points out userspace can not only remove the port from the bridge,
it could also place the device in a different virtual device, e.g.
macvlan.

If this happens, we must drop the packet, there is no way for us to
reinject it into the bridge path.

Switch to _upper API, we don't need the bridge port structure.
Also, this fix keeps another bug intact:

Both nfnetlink_log and nfnetlink_queue use CONFIG_BRIDGE_NETFILTER
too aggressive, which prevents certain logging features when queueing
in bridge family: NETFILTER_FAMILY_BRIDGE can be enabled while the old
CONFIG_BRIDGE_NETFILTER cruft is off.

Fixes tag is a common ancestor, this was always broken.

Fixes: f350a0a87374 ("bridge: use rx_handler_data pointer to store net_bridge_port pointer")
Reported-by: Ji'an Zhou <eilaimemedsnaimel@gmail.com>
Assisted-by: Claude:claude-sonnet-4-6
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
netfilter: disable payload mangling in userns 2026-05-22T10:28:46+00:00 Florian Westphal fw@strlen.de 2026-05-16T15:23:21+00:00 968cc2c96390f06e56ed6a43f935bfebdefed28f Several parts of network stack rely on iph->ihl validation done by network stack before PRE_ROUTING. Disable this feature for user namespaces for now. tcp option handling is likely safe even for LOCAL_IN, so this this leaves tcp option mangling via nft_exthdr.c as-is. I don't think these are the only means to alter packets, but these appear to be relatively prominent. This could be relaxed later. Example: - allow userns for ingress hook. - allow userns if base is transport header. Also, we should revalidate or restrict generally: - Don't allow linklayer writes to spill into network header - restrict ipv4 and ipv6 to 'known safe' writes, e.g. saddr/daddr/check/tos Reported-by: Qi Tang <tpluszz77@gmail.com> Reported-by: Tong Liu <lyutoon@gmail.com> Tested-by: Qi Tang <tpluszz77@gmail.com> Link: https://lore.kernel.org/netfilter-devel/20260515100411.3141-1-fw@strlen.de/ Signed-off-by: Florian Westphal <fw@strlen.de> 
Several parts of network stack rely on iph->ihl validation
done by network stack before PRE_ROUTING.

Disable this feature for user namespaces for now.

tcp option handling is likely safe even for LOCAL_IN, so this
this leaves tcp option mangling via nft_exthdr.c as-is.

I don't think these are the only means to alter packets, but these
appear to be relatively prominent.

This could be relaxed later.  Example:
 - allow userns for ingress hook.
 - allow userns if base is transport header.

 Also, we should revalidate or restrict generally:
 - Don't allow linklayer writes to spill into network header
 - restrict ipv4 and ipv6 to 'known safe' writes, e.g.
   saddr/daddr/check/tos

Reported-by: Qi Tang <tpluszz77@gmail.com>
Reported-by: Tong Liu <lyutoon@gmail.com>
Tested-by: Qi Tang <tpluszz77@gmail.com>
Link: https://lore.kernel.org/netfilter-devel/20260515100411.3141-1-fw@strlen.de/
Signed-off-by: Florian Westphal <fw@strlen.de>
netfilter: nf_queue: hold bridge skb->dev while queued 2026-05-16T11:23:01+00:00 Haoze Xie royenheart@gmail.com 2026-05-15T03:19:02+00:00 e196115ec330a18de415bdb9f5071aa9f08e53ce br_pass_frame_up() rewrites skb->dev from the ingress port to the bridge master before queueing bridge LOCAL_IN packets. NFQUEUE only holds references on state.in/out and bridge physdevs, so a queued bridge packet can retain a freed bridge master in skb->dev until reinjection. When the verdict is reinjected later, br_netif_receive_skb() re-enters the receive path with skb->dev still pointing at the freed bridge master, triggering a use-after-free. Store skb->dev in the queue entry, hold a reference on it for the queue lifetime, and use the saved device when dropping queued packets during NETDEV_DOWN handling. Fixes: ac2863445686 ("netfilter: bridge: add nf_afinfo to enable queuing to userspace") Cc: stable@kernel.org Reported-by: Yuan Tan <yuantan098@gmail.com> Reported-by: Yifan Wu <yifanwucs@gmail.com> Reported-by: Juefei Pu <tomapufckgml@gmail.com> Reported-by: Xin Liu <bird@lzu.edu.cn> Signed-off-by: Haoze Xie <royenheart@gmail.com> Signed-off-by: Ren Wei <n05ec@lzu.edu.cn> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> 
br_pass_frame_up() rewrites skb->dev from the ingress port to the bridge
master before queueing bridge LOCAL_IN packets. NFQUEUE only holds
references on state.in/out and bridge physdevs, so a queued bridge
packet can retain a freed bridge master in skb->dev until reinjection.

When the verdict is reinjected later, br_netif_receive_skb() re-enters
the receive path with skb->dev still pointing at the freed bridge master,
triggering a use-after-free.

Store skb->dev in the queue entry, hold a reference on it for the queue
lifetime, and use the saved device when dropping queued packets during
NETDEV_DOWN handling.

Fixes: ac2863445686 ("netfilter: bridge: add nf_afinfo to enable queuing to userspace")
Cc: stable@kernel.org
Reported-by: Yuan Tan <yuantan098@gmail.com>
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Reported-by: Xin Liu <bird@lzu.edu.cn>
Signed-off-by: Haoze Xie <royenheart@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
netfilter: nfnetlink: prefer skb_mac_header helpers 2026-04-10T10:16:26+00:00 Florian Westphal fw@strlen.de 2026-04-04T10:09:05+00:00 74feb7d373b32a63d7986a2caf9689c860c9a761 This adds implicit DEBUG_WARN_ON_ONCE for debug configurations. No other changes intended. Signed-off-by: Florian Westphal <fw@strlen.de> 
This adds implicit DEBUG_WARN_ON_ONCE for debug configurations.
No other changes intended.

Signed-off-by: Florian Westphal <fw@strlen.de>
Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2026-04-09T20:20:59+00:00 Jakub Kicinski kuba@kernel.org 2026-04-02T17:57:09+00:00 b6e39e48469e37057fce27a1b87cf6d3e456aa42 Cross-merge networking fixes after downstream PR (net-7.0-rc8). Conflicts: net/ipv6/seg6_iptunnel.c c3812651b522f ("seg6: separate dst_cache for input and output paths in seg6 lwtunnel") 78723a62b969a ("seg6: add per-route tunnel source address") https://lore.kernel.org/adZhwtOYfo-0ImSa@sirena.org.uk net/ipv4/icmp.c fde29fd934932 ("ipv4: icmp: fix null-ptr-deref in icmp_build_probe()") d98adfbdd5c01 ("ipv4: drop ipv6_stub usage and use direct function calls") https://lore.kernel.org/adO3dccqnr6j-BL9@sirena.org.uk Adjacent changes: drivers/net/ethernet/stmicro/stmmac/chain_mode.c 51f4e090b9f8 ("net: stmmac: fix integer underflow in chain mode") 6b4286e05508 ("net: stmmac: rename STMMAC_GET_ENTRY() -> STMMAC_NEXT_ENTRY()") Signed-off-by: Jakub Kicinski <kuba@kernel.org> 
Cross-merge networking fixes after downstream PR (net-7.0-rc8).

Conflicts:

net/ipv6/seg6_iptunnel.c
  c3812651b522f ("seg6: separate dst_cache for input and output paths in seg6 lwtunnel")
  78723a62b969a ("seg6: add per-route tunnel source address")
https://lore.kernel.org/adZhwtOYfo-0ImSa@sirena.org.uk

net/ipv4/icmp.c
  fde29fd934932 ("ipv4: icmp: fix null-ptr-deref in icmp_build_probe()")
  d98adfbdd5c01 ("ipv4: drop ipv6_stub usage and use direct function calls")
https://lore.kernel.org/adO3dccqnr6j-BL9@sirena.org.uk

Adjacent changes:

drivers/net/ethernet/stmicro/stmmac/chain_mode.c
  51f4e090b9f8 ("net: stmmac: fix integer underflow in chain mode")
  6b4286e05508 ("net: stmmac: rename STMMAC_GET_ENTRY() -> STMMAC_NEXT_ENTRY()")

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
netfilter: nfnetlink_queue: make hash table per queue 2026-04-08T11:34:51+00:00 Florian Westphal fw@strlen.de 2026-04-07T15:00:01+00:00 936206e3f6ff411581e615e930263d6f8b78df9d Sharing a global hash table among all queues is tempting, but it can cause crash: BUG: KASAN: slab-use-after-free in nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue] [..] nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue] nfnetlink_rcv_msg+0x46a/0x930 kmem_cache_alloc_node_noprof+0x11e/0x450 struct nf_queue_entry is freed via kfree, but parallel cpu can still encounter such an nf_queue_entry when walking the list. Alternative fix is to free the nf_queue_entry via kfree_rcu() instead, but as we have to alloc/free for each skb this will cause more mem pressure. Cc: Scott Mitchell <scott.k.mitch1@gmail.com> Fixes: e19079adcd26 ("netfilter: nfnetlink_queue: optimize verdict lookup with hash table") Signed-off-by: Florian Westphal <fw@strlen.de> 
Sharing a global hash table among all queues is tempting, but
it can cause crash:

BUG: KASAN: slab-use-after-free in nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue]
[..]
 nfqnl_recv_verdict+0x11ac/0x15e0 [nfnetlink_queue]
 nfnetlink_rcv_msg+0x46a/0x930
 kmem_cache_alloc_node_noprof+0x11e/0x450

struct nf_queue_entry is freed via kfree, but parallel cpu can still
encounter such an nf_queue_entry when walking the list.

Alternative fix is to free the nf_queue_entry via kfree_rcu() instead,
but as we have to alloc/free for each skb this will cause more mem
pressure.

Cc: Scott Mitchell <scott.k.mitch1@gmail.com>
Fixes: e19079adcd26 ("netfilter: nfnetlink_queue: optimize verdict lookup with hash table")
Signed-off-by: Florian Westphal <fw@strlen.de>
netfilter: add more netlink-based policy range checks 2026-04-08T05:51:30+00:00 Florian Westphal fw@strlen.de 2026-03-09T23:26:46+00:00 66b75e6bbeeb489156a74534561bbbd360843a73 These spots either already check the attribute range manually before use or the consuming functions tolerate unexpected values. Nevertheless, add more range checks via netlink policy so we gain more users and avoid possible re-use in other places that might not have the required manual checks. This also improves error reporting: netlink core can generate extack errors. Signed-off-by: Florian Westphal <fw@strlen.de> 
These spots either already check the attribute range manually
before use or the consuming functions tolerate unexpected values.

Nevertheless, add more range checks via netlink policy so we gain
more users and avoid possible re-use in other places that might
not have the required manual checks.  This also improves error
reporting: netlink core can generate extack errors.

Signed-off-by: Florian Westphal <fw@strlen.de>