linux-stable.git/net/ipv4, branch v6.12.96

net: ipv4: bound TCP reordering sysctl writes and MTU probe sizes

2026-07-18T14:52:03+00:00

commit efb8763d7bbb40cff4cc55a6b62c3095a038149c upstream.

Reject invalid `net.ipv4.tcp_reordering` values before they reach TCP
socket state. The sysctl is stored as an `int` but copied into the
`u32` `tp->reordering` field for new sockets, so negative writes wrap
to large values.

With `tcp_mtu_probing=2`, the wrapped value can overflow the
`tcp_mtu_probe()` size calculation and drive the MTU probing path into
an out-of-bounds read. Route `tcp_reordering` writes through
`proc_dointvec_minmax()` and require it to be at least 1. Also require
`tcp_max_reordering` to be at least 1 so the configured maximum cannot
become negative either.

When registering the table for a non-init network namespace, relocate
`extra2` pointers that refer into `init_net.ipv4` so the
`tcp_reordering` upper bound follows that namespace's
`tcp_max_reordering`.

Harden `tcp_mtu_probe()` itself by computing `size_needed` as `u64`.
This keeps the send queue and window checks from being bypassed through
signed integer overflow.

Fixes: 91cc17c0e5e5 ("[TCP]: MTUprobe: receiver window & data available checks fixed")
Cc: stable@vger.kernel.org
Reported-by: Yuan Tan 
Reported-by: Zhengchuan Liang 
Reported-by: Xin Liu 
Suggested-by: Eric Dumazet 
Signed-off-by: Wyatt Feng 
Signed-off-by: Ren Wei 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/1a5b7e1ef4d70fbad8c8ee0b82d8405f3c964a3d.1781395200.git.bronzed_45_vested@icloud.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

ipv4: igmp: remove multicast group from hash table on device destruction

2026-07-18T14:52:03+00:00

commit 7993211bde166471dffac074dc965489f86531f8 upstream.

When a device is destroyed under RTNL, ip_mc_destroy_dev() iterates through
the multicast list and calls ip_ma_put() on each membership, scheduling
them for RCU reclamation. However, they are not unlinked from the device's
multicast hash table (mc_hash).

Since the device remains published in dev->ip_ptr until after
ip_mc_destroy_dev() completes, concurrent RCU readers traversing mc_hash
can still locate and access the multicast group after its refcount is
decremented. If the RCU callback runs and frees the group while a reader is
accessing it, a use-after-free occurs.

Fix this by unlinking the multicast group from mc_hash using
ip_mc_hash_remove() before scheduling it for reclamation.

BUG: KASAN: slab-use-after-free in ip_check_mc_rcu+0x149/0x3f0
Read of size 4 at addr ffff888009bf1408 by task mausezahn/2276

Call Trace:
 
 dump_stack_lvl+0x67/0x90
 print_report+0x175/0x7c0
 kasan_report+0x147/0x180
 ip_check_mc_rcu+0x149/0x3f0
 udp_v4_early_demux+0x36d/0x12d0
 ip_rcv_finish_core+0xb8b/0x1390
 ip_rcv_finish+0x54/0x120
 NF_HOOK+0x213/0x2b0
 __netif_receive_skb+0x126/0x340
 process_backlog+0x4f2/0xf00
 __napi_poll+0x92/0x2c0
 net_rx_action+0x583/0xc60
 handle_softirqs+0x236/0x7f0
 do_softirq+0x57/0x80
 

Allocated by task 2239:
 kasan_save_track+0x3e/0x80
 __kasan_kmalloc+0x72/0x90
 ____ip_mc_inc_group+0x31a/0xa40
 __ip_mc_join_group+0x334/0x3f0
 do_ip_setsockopt+0x16fa/0x2010
 ip_setsockopt+0x3f/0x90
 do_sock_setsockopt+0x1ad/0x300

Freed by task 0:
 kasan_save_track+0x3e/0x80
 kasan_save_free_info+0x40/0x50
 __kasan_slab_free+0x3a/0x60
 __rcu_free_sheaf_prepare+0xd4/0x220
 rcu_free_sheaf+0x36/0x190
 rcu_core+0x8d9/0x12f0
 handle_softirqs+0x236/0x7f0

Fixes: e9897071350b ("igmp: hash a hash table to speedup ip_check_mc_rcu()")
Cc: stable@vger.kernel.org
Signed-off-by: Yuyang Huang 
Reviewed-by: Kuniyuki Iwashima 
Reviewed-by: Ido Schimmel 
Link: https://patch.msgid.link/20260701235014.73505-1-yuyanghuang@google.com
Signed-off-by: Paolo Abeni 
Signed-off-by: Greg Kroah-Hartman

net/tcp-ao: fix use-after-free of key in del_async path

2026-07-04T11:43:36+00:00

commit 5ba9950bc9078e19b69cca1e56d1553b125c6857 upstream.

In tcp_ao_delete_key(), the del_async path skips the current_key
and rnext_key validity checks present in the synchronous path,
assuming these pointers are always NULL on LISTEN sockets.  However,
if a key was added with set_current=1/set_rnext=1 while the socket
was in CLOSE state, current_key and rnext_key will be non-NULL
after listen() transitions the socket to LISTEN.

When such a key is deleted with del_async=1, hlist_del_rcu() and
call_rcu() free the key without clearing the dangling pointers.
After the RCU grace period, getsockopt(TCP_AO_INFO) dereferences
current_key->sndid and rnext_key->rcvid from freed slab memory.

Clear current_key and rnext_key in the del_async path when they
reference the key being deleted.

Fixes: d6732b95b6fb ("net/tcp: Allow asynchronous delete for TCP-AO keys (MKTs)")
Signed-off-by: HanQuan 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20260623015208.1191687-1-eilaimemedsnaimel@gmail.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: ip_gre: require CAP_NET_ADMIN in the device netns for changelink

2026-07-04T11:43:32+00:00

commit 8165f7ff57d9667d2bb477ef6af83ede7fed4ad7 upstream.

A tunnel changelink() operates on at most two netns, dev_net(dev) and
the tunnel link netns t->net. They differ once the device is created in
or moved to a netns other than the one the request runs in. The rtnl
changelink path checks CAP_NET_ADMIN only against dev_net(dev), so a
caller privileged there but not in t->net can rewrite a tunnel that
lives in t->net.

Add rtnl_dev_link_net_capable() next to rtnl_get_net_ns_capable() in
net/core/rtnetlink.c. It requires CAP_NET_ADMIN in the link netns and is
skipped when the link netns is dev_net(dev), where the rtnl path already
checked it. The other patches in this series use the same helper.

Gate ipgre_changelink() and erspan_changelink() with it, at the top of
the op before any attribute is parsed, because the parsers update live
tunnel fields first. ipgre_netlink_parms() sets t->collect_md before
ip_tunnel_changelink() runs.

Commit 8b484efd5cb4 ("ip6: vti: Use ip6_tnl.net in
vti6_siocdevprivate().") added the same check on the ioctl path. This
adds it on RTM_NEWLINK.

Reported-by: Xiao Liang 
Closes: https://lore.kernel.org/netdev/CABAhCOSzP1vaThGV35_VnsRCb=87_CPjPVsTHbq905k8A+BuUg@mail.gmail.com/
Fixes: b57708add314 ("gre: add x-netns support")
Cc: stable@vger.kernel.org
Signed-off-by: Maoyi Xie 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20260612085941.3158249-2-maoyixie.tju@gmail.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

ipv4: account for fraggap on the paged allocation path

2026-07-04T11:43:31+00:00

[ Upstream commit eca856950f7cb1a221e02b99d758409f2c5cec42 ]

In __ip_append_data(), when the paged-allocation branch is taken,
alloclen and pagedlen are computed as

	alloclen = fragheaderlen + transhdrlen;
	pagedlen = datalen - transhdrlen;

datalen already includes fraggap, but the fraggap bytes carried over
from the previous skb are copied into the new skb's linear area at
offset transhdrlen by the subsequent skb_copy_and_csum_bits(). The
linear area is therefore undersized by fraggap bytes while pagedlen is
overstated by the same amount.

The non-paged branch sets alloclen to fraglen, which already accounts
for fraggap because datalen does. Bring the paged branch in line by
adding fraggap to alloclen and subtracting it from pagedlen.

After this adjustment, copy no longer collapses to -fraggap on the
paged path, so remove the stale comment describing that old arithmetic.

Fixes: 8eb77cc73977 ("ipv4: avoid partial copy for zc")
Signed-off-by: Jungwoo Lee 
Signed-off-by: Wongi Lee 
Reviewed-by: Ido Schimmel 
Link: https://patch.msgid.link/ajFR1eLAIs42TN3g@DESKTOP-19IMU7U.localdomain
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin

inet: add indirect call wrapper for getfrag() calls

2026-07-04T11:43:31+00:00

[ Upstream commit 5204ccbfa22358f95afd031a3f337e6d9a74baea ]

UDP send path suffers from one indirect call to ip_generic_getfrag()

We can use INDIRECT_CALL_1() to avoid it.

Signed-off-by: Eric Dumazet 
Reviewed-by: Willem de Bruijn 
Reviewed-by: Brian Vazquez 
Link: https://patch.msgid.link/20241203173617.2595451-1-edumazet@google.com
Signed-off-by: Jakub Kicinski 
Stable-dep-of: eca856950f7c ("ipv4: account for fraggap on the paged allocation path")
Signed-off-by: Sasha Levin

tcp: secure_seq: add back ports to TS offset

2026-06-19T11:42:39+00:00

[ Upstream commit 165573e41f2f66ef98940cf65f838b2cb575d9d1 ]

This reverts 28ee1b746f49 ("secure_seq: downgrade to per-host timestamp offsets")

tcp_tw_recycle went away in 2017.

Zhouyan Deng reported off-path TCP source port leakage via
SYN cookie side-channel that can be fixed in multiple ways.

One of them is to bring back TCP ports in TS offset randomization.

As a bonus, we perform a single siphash() computation
to provide both an ISN and a TS offset.

Fixes: 28ee1b746f49 ("secure_seq: downgrade to per-host timestamp offsets")
Reported-by: Zhouyan Deng 
Signed-off-by: Eric Dumazet 
Reviewed-by: Kuniyuki Iwashima 
Acked-by: Florian Westphal 
Link: https://patch.msgid.link/20260302205527.1982836-1-edumazet@google.com
Signed-off-by: Jakub Kicinski 
(cherry picked from commit 165573e41f2f66ef98940cf65f838b2cb575d9d1)
[kept the DCCP functions in the header, as DCCP was not retired yet
 in 6.12]
Signed-off-by: Heiko Stuebner 
Signed-off-by: Greg Kroah-Hartman

tcp: use EXPORT_IPV6_MOD[_GPL]()

2026-06-19T11:42:39+00:00

[ Upstream commit 6dc4c2526f6d11f36c4e26d0231b345eabab584c ]

Use EXPORT_IPV6_MOD[_GPL]() for symbols that don't need
to be exported unless CONFIG_IPV6=m

tcp_hashinfo and tcp_openreq_init_rwin() are no longer
used from any module anyway.

Signed-off-by: Eric Dumazet 
Reviewed-by: Kuniyuki Iwashima 
Reviewed-by: Mateusz Polchlopek 
Link: https://patch.msgid.link/20250212132418.1524422-4-edumazet@google.com
Signed-off-by: Jakub Kicinski 
(cherry picked from commit 6dc4c2526f6d11f36c4e26d0231b345eabab584c)
[needed as dependency for tcp: secure_seq: add back ports to TS offset]
Signed-off-by: Heiko Stuebner 
Signed-off-by: Greg Kroah-Hartman

netfilter: nft_fib: fix stale stack leak via the OIFNAME register

2026-06-19T11:42:37+00:00

[ Upstream commit ab185e0c4fb82dfba6fb86f8271e06f931d9c64c ]

For NFT_FIB_RESULT_OIFNAME the destination register is declared with
len = IFNAMSIZ (four 32-bit registers), but on the lookup-fail,
RTN_LOCAL and oif-mismatch paths nft_fib{4,6}_eval() only writes one
register via "*dest = 0". The remaining three registers are left as
whatever was on the stack in nft_do_chain()'s struct nft_regs, and a
downstream expression that loads the register span can leak that
uninitialised kernel stack to userspace.

The NFTA_FIB_F_PRESENT existence check has the same shape: it is only
meaningful for NFT_FIB_RESULT_OIF, yet it was accepted for any result type
while the eval stores a single byte via nft_reg_store8(), leaving the rest
of the declared span stale.

Fix both:

 - replace the bare "*dest = 0" in the eval with nft_fib_store_result(),
   which strscpy_pad()s the whole IFNAMSIZ for OIFNAME (and is already
   used on the other early-return path), and

 - restrict NFTA_FIB_F_PRESENT to NFT_FIB_RESULT_OIF and declare its
   destination as a single u8, so the marked span matches the one byte
   the eval writes.

Fixes: f6d0cbcf09c5 ("netfilter: nf_tables: add fib expression")
Suggested-by: Florian Westphal 
Cc: stable@vger.kernel.org
Signed-off-by: Davide Ornaghi 
Signed-off-by: Pablo Neira Ayuso 
[ kept the tree's older `ip6_route_lookup()`/`rt6_info` IPv6 context and changed only `*dest = 0;` to `nft_fib_store_result(dest, priv, NULL);` ]
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

inet: frags: fix use-after-free caused by the fqdir_pre_exit() flush

2026-06-19T11:42:31+00:00

commit 32594b09854970d7ba83eb2dc8c69a2edd158c8e upstream.

On netns teardown, fqdir_pre_exit() walks the fqdir rhashtable and
flushes every fragment queue that is not yet complete using
inet_frag_queue_flush(). That helper frees all the skbs queued on the
fragment queue but does not set INET_FRAG_COMPLETE, and leaves
q->fragments_tail and q->last_run_head pointing at the freed skbs.
The queue itself stays in the rhashtable.

fqdir_pre_exit() first lowers high_thresh to 0 to stop new queue lookups,
but it cannot stop a fragment that already obtained the queue through
inet_frag_find() earlier and stalled just before taking the queue lock.
Once that fragment resumes after the flush and takes the queue lock,
it passes the INET_FRAG_COMPLETE check and then dereferences the freed
fragments_tail. inet_frag_queue_insert() reads FRAG_CB() and ->len of
that pointer and, on the append path, writes ->next_frag, causing a
slab use-after-free. IPv6, nf_conntrack_reasm6 and 6lowpan reassembly
share the same flush path and are affected as well.

Reset rb_fragments, fragments_tail and last_run_head in
inet_frag_queue_flush() so a flushed queue no longer points at the
freed skbs. A fragment that resumes after the flush and takes the
queue lock then finds an empty queue and starts a new run instead of
dereferencing the freed fragments_tail. ip_frag_reinit() already
performed this reset after its own flush, so drop the now duplicate
code there.

Cc: stable@vger.kernel.org
Fixes: 006a5035b495 ("inet: frags: flush pending skbs in fqdir_pre_exit()")
Suggested-by: Eric Dumazet 
Signed-off-by: Hyunwoo Kim 
Link: https://patch.msgid.link/ah6ukYq5G98LshdA@v4bel
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman