linux.git/net/l2tp, branch v7.2

l2tp: fix tunnel and session refcount leak on seq_file release

2026-08-13T09:49:31+00:00

In pppol2tp_proc_open() and l2tp_dfs_seq_open(), iteration state
(pd->tunnel and pd->session) is kept in seq_file private data to allow
iteration across multiple read() system calls.

However, if userspace closes /proc/net/pppol2tp or /sys/kernel/debug/l2tp/tunnels
before reading to end-of-file (EOF), any tunnel or session reference stored in
pd->tunnel / pd->session is left un-dropped when seq_file private data is freed.

Fix this by dropping any remaining pd->tunnel and pd->session references in
pppol2tp_proc_release() and l2tp_dfs_seq_release() when closing the file.

Fixes: 0e0c3fee3a59 ("l2tp: hold reference on tunnels printed in pppol2tp proc file")
Fixes: f726214d9b23 ("l2tp: hold reference on tunnels printed in l2tp/tunnels debugfs file")
Reported-by: syzbot+d6fa74e3f19d6ee01e3a@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a760f32.01d0871a.3a0d52.004f.GAE@google.com/T/#u
Assisted-by: Jetski:Gemini-3.1-Pro
Cc: James Chapman 
Cc: Guillaume Nault 
Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20260811144651.2733424-1-edumazet@google.com
Signed-off-by: Paolo Abeni

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-06-04T22:29:04+00:00

Cross-merge networking fixes after downstream PR (net-7.1-rc7).

Silent conflicts:

net/wireless/nl80211.c
  cb9959ab5f99 ("wifi: cfg80211: enforce HE/EHT cap/oper consistency")
  a384ae969902 ("wifi: cfg80211: move AP HT/VHT/... operation to beacon info")
https://lore.kernel.org/aiGJDaHV4UlCexIQ@sirena.org.uk

Conflicts:

drivers/net/wireless/intel/iwlwifi/mld/ap.c
  a342c99cb70d ("wifi: iwlwifi: mld: honor BSS_CHANGED_BEACON_ENABLED")
  9bf1b409afc7 ("wifi: iwlwifi: mld: send tx power constraints before link activation")
https://lore.kernel.org/ah2bfedhV45ZxMO8@sirena.org.uk

drivers/net/wireless/intel/iwlwifi/pcie/drv.c
  093305d801fa ("wifi: iwlwifi: pcie: simplify the resume flow if fast resume is not used")
  e2323929a68a ("wifi: iwlwifi: pcie: add debug print for resume flow if powered off")
https://lore.kernel.org/ah2bfedhV45ZxMO8@sirena.org.uk

Adjacent changes:

drivers/net/ethernet/airoha/airoha_eth.c
  b38cae85d1c4 ("net: airoha: Fix use-after-free in metadata dst teardown")
  ec6c391bcca7 ("net: airoha: Introduce airoha_gdm_dev struct")

drivers/net/ethernet/microchip/lan743x_main.c
  8173d22b211f ("net: lan743x: permit VLAN-tagged packets up to configured MTU")
  e3c6508a46f5 ("net: lan743x: avoid netdev-based logging before netdev registration")

Signed-off-by: Jakub Kicinski

l2tp: pppol2tp: hold reference to session in pppol2tp_ioctl()

2026-06-02T02:40:46+00:00

pppol2tp_ioctl() read sock->sk->sk_user_data directly without any
locks or reference counting.  If a controllable sleep was induced during
copy_from_user() (e.g. via a userfaultfd page fault sleep), a concurrent
socket close could trigger pppol2tp_session_close() asynchronously.  This
frees the l2tp_session structure via the l2tp_session_del_work workqueue.
Upon resuming, the ioctl thread dereferences the stale session pointer,
resulting in a Use-After-Free (UAF).

Fix this by securely fetching the session reference using the RCU-safe,
refcounted helper pppol2tp_sock_to_session(sk) on entry.  This locks the
session's refcount across the sleep.  We structured the function to exit
via standard err breaks, guaranteeing that l2tp_session_put() is cleanly
called on all return paths to drop the reference.

To preserve existing behavior we validate the session and its magic
signature only for the specific L2TP commands that require it.  This
ensures that generic/unknown ioctls called on an unconnected socket
still return -ENOIOCTLCMD and correctly fall back to generic handlers
(e.g. in sock_do_ioctl()).

Signed-off-by: Lee Jones 
Fixes: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Link: https://patch.msgid.link/20260527133630.2120612-1-lee@kernel.org
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-05-28T21:02:21+00:00

Cross-merge networking fixes after downstream PR (net-7.1-rc6).

Conflicts:

drivers/net/phy/air_en8811h.c
  d895767c33781 ("net: phy: air_en8811h: add AN8811HB MCU assert/deassert support")
  dddfadd75197e ("net: phy: Add Airoha phy library for shared code")
  5226bb6634cdf ("net: phy: air_phy_lib: Factorize BuckPBus register accessors")
  e08f0ea6daf2e ("net: phy: Rename Airoha common BuckPBus register accessors")

net/sched/sch_netem.c
  a2f6ed7b4873 ("net/sched: netem: add per-impairment extended statistics")
  9552b11e3eda ("net/sched: fix packet loop on netem when duplicate is on")

Adjacent changes:

drivers/dpll/zl3073x/core.c
  c1224569cef0 ("dpll: zl3073x: make frequency monitor a per-device attribute")
  54e65df8cf18 ("dpll: zl3073x: report FFO as DPLL vs input reference offset")

net/iucv/af_iucv.c
  347fdd4df85f ("af_iucv: convert to getsockopt_iter")
  3589d20a666c ("net/iucv: fix locking in .getsockopt")

Signed-off-by: Jakub Kicinski

l2tp: use refcount_inc_not_zero in l2tp_session_get_by_ifname

2026-05-27T00:35:12+00:00

A reader in l2tp_session_get_by_ifname() can return a pointer to a
session whose refcount has reached zero. The getter takes its
reference with plain refcount_inc(), but every other session getter
in the same file (l2tp_v2_session_get, l2tp_v3_session_get, and the
corresponding _get_next variants) uses refcount_inc_not_zero()
because the IDR/RCU lookup can race with refcount_dec_and_test() ->
l2tp_session_free() -> kfree_rcu(). The ifname getter is the only
outlier; the inconsistency was raised on-list after 979c017803c4
("l2tp: use list_del_rcu in l2tp_session_unhash").

A reader inside rcu_read_lock_bh() that matches session->ifname can
be preempted between the strcmp() and the refcount_inc(). If the
last reference drops on another CPU in that window, the reader's
refcount_inc() runs on a counter that has reached zero. refcount_t
catches the addition-on-zero, prints "refcount_t: addition on 0;
use-after-free", saturates the counter, and returns the saturated
pointer to the caller. Session memory is held live by the in-flight
RCU read section, but the kfree_rcu() callback queued from
l2tp_session_free() will free it once the grace period closes; a
caller that dereferences the returned session past that point hits
a slab-use-after-free. On PREEMPT_RT local_bh_disable() is a per-CPU
sleeping lock and the preemption window is real; on stock PREEMPT
kernels local_bh_disable() is a preempt_count increment that closes
the cross-CPU race in practice (see below).

Use refcount_inc_not_zero() and continue the list walk on failure,
matching the other session getters in the file. The ifname getter
is the only session getter in net/l2tp/ that still uses the bare
refcount_inc() pattern; this change restores file-internal
consistency. The success path is unchanged.

Fixes: abe7a1a7d0b6 ("l2tp: improve tunnel/session refcount helpers")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Bommarito 
Reviewed-by: James Chapman 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20260523023423.2568972-1-michael.bommarito@gmail.com
Signed-off-by: Jakub Kicinski

l2tp: ppp: convert to getsockopt_iter

2026-05-22T18:11:09+00:00

Convert PPPoL2TP socket's getsockopt implementation to use the new
getsockopt_iter callback with sockopt_t.

Key changes:
- Replace (char __user *optval, int __user *optlen) with sockopt_t *opt
- Use opt->optlen for buffer length (input) and returned size (output)
- Use copy_to_iter() instead of put_user()/copy_to_user()

Acked-by: Stanislav Fomichev 
Signed-off-by: Breno Leitao 
Link: https://patch.msgid.link/20260520-getsock_four-v3-4-b8c0b16b7780@debian.org
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-05-21T22:09:02+00:00

Cross-merge networking fixes after downstream PR (net-7.1-rc5).

No conflicts, adjacent changes:

drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c
  cc199cd1b912 ("net/mlx5e: Reduce branches in napi poll")
  c326f9c68921 ("net/mlx5e: xsk: Fix unlocked writing to ICOSQ")

drivers/net/ethernet/mellanox/mlx5/core/eswitch.c
  c6df9a65cbb0 ("net/mlx5: Skip disabled vports when setting max TX speed")
  1fba57c91416 ("net/mlx5: Add VHCA_ID page management mode support")

net/mac80211/mlme.c
  a6e6ccd5bd07 ("wifi: mac80211: consume only present negotiated TTLM maps")
  49e62ec6eb06 ("wifi: mac80211: move frame RX handling to type files")

Signed-off-by: Jakub Kicinski

l2tp: use list_del_rcu in l2tp_session_unhash

2026-05-21T15:47:20+00:00

An unprivileged local user can pin a host CPU indefinitely in
l2tp_session_get_by_ifname() by issuing L2TP_CMD_SESSION_GET on
L2TP_ATTR_IFNAME concurrently with L2TP_CMD_SESSION_CREATE and
L2TP_CMD_SESSION_DELETE on the same tunnel. All three commands take
GENL_UNS_ADMIN_PERM, so CAP_NET_ADMIN in the netns user namespace
suffices; on any host that has l2tp_core loaded the trigger is
reachable from a standard `unshare -Urn` sandbox.

l2tp_session_unhash() removes a session from tunnel->session_list
with list_del_init(), but that list is walked by
l2tp_session_get_by_ifname() with list_for_each_entry_rcu() under
rcu_read_lock_bh(). list_del_init() leaves the deleted entry's
next/prev self-pointing; a reader that has loaded the entry and
then advances pos->list.next reads &session->list, container_of()s
back to the same session, and list_for_each_entry_rcu() never
reaches the list head. The CPU stays in strcmp() inside the
walker, with BH and preemption disabled, so RCU grace periods on
the host stall behind it and the wedged thread cannot be killed
(SIGKILL is delivered on syscall return).

Use list_del_rcu() to match the existing list_add_rcu() in
l2tp_session_register(); the deleted session remains visible to
in-flight walkers with consistent next/prev pointers until
kfree_rcu() in l2tp_session_free() releases it. tunnel->session_list
has exactly one list_del_init() call site; the list_del_init
(&session->clist) at l2tp_core.c:533 operates on the per-collision
list, which is not walked under RCU. list_empty(&session->list) is
not used anywhere in net/l2tp/ after the unhash point, so dropping
the post-delete self-init is safe; the fix has no userspace-visible
behavior change.

Fixes: 89b768ec2dfef ("l2tp: use rcu list add/del when updating lists")
Cc: stable@vger.kernel.org # 6.11+
Signed-off-by: Michael Bommarito 
Link: https://patch.msgid.link/20260518183447.64078-1-michael.bommarito@gmail.com
Signed-off-by: Jakub Kicinski

udp_tunnel: Pass struct sock to setup_udp_tunnel_sock().

2026-05-06T00:47:04+00:00

None of the udp_tunnel users need struct socket in their
fast paths; it is only used for tunnel setup / teardown.

Even setup_udp_tunnel_sock() does not need struct socket.

Let's change setup_udp_tunnel_sock() to take struct sock
instead of struct socket.

Signed-off-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20260502031401.3557229-3-kuniyu@google.com
Signed-off-by: Jakub Kicinski

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2026-04-09T20:20:59+00:00

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