linux-stable.git/net/core, branch v6.6.153

net: harmonize tstats and dstats

2026-08-23T12:20:07+00:00

commit d3ed6dee73c560fad0a8e152c8e233b3fb3a2e44 upstream.

After the blamed commits below, some UDP tunnel use dstats for
accounting. On the xmit path, all the UDP-base tunnels ends up
using iptunnel_xmit_stats() for stats accounting, and the latter
assumes the relevant (tunnel) network device uses tstats.

The end result is some 'funny' stat report for the mentioned UDP
tunnel, e.g. when no packet is actually dropped and a bunch of
packets are transmitted:

gnv2:  mtu 1450 qdisc noqueue \
		state UNKNOWN mode DEFAULT group default qlen 1000
    link/ether ee:7d:09:87:90:ea brd ff:ff:ff:ff:ff:ff
    RX:  bytes packets errors dropped  missed   mcast
         14916      23      0      15       0       0
    TX:  bytes packets errors dropped carrier collsns
             0    1566      0       0       0       0

Address the issue ensuring the same binary layout for the overlapping
fields of dstats and tstats. While this solution is a bit hackish, is
smaller and with no performance pitfall compared to other alternatives
i.e. supporting both dstat and tstat in iptunnel_xmit_stats() or
reverting the blamed commit.

With time we should possibly move all the IP-based tunnel (and virtual
devices) to dstats.

Fixes: c77200c07491 ("bareudp: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Fixes: 6fa6de302246 ("geneve: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Fixes: be226352e8dc ("vxlan: Handle stats using NETDEV_PCPU_STAT_DSTATS.")
Signed-off-by: Paolo Abeni 
Reviewed-by: Guillaume Nault 
Link: https://patch.msgid.link/2e1c444cf0f63ae472baff29862c4c869be17031.1738432804.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: sched: Move drop_reason to struct tc_skb_cb

2026-08-23T12:20:06+00:00

[ Upstream commit fb2780721ca5e9f78bbe4544b819b929a982df9c ]

Move drop_reason from struct tcf_result to skb cb - more specifically to
struct tc_skb_cb. With that, we'll be able to also set the drop reason for
the remaining qdiscs (aside from clsact) that do not have access to
tcf_result when time comes to set the skb drop reason.

Signed-off-by: Victor Nogueira 
Acked-by: Daniel Borkmann 
Reviewed-by: Simon Horman 
Signed-off-by: David S. Miller 
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin

net, sched: Make tc-related drop reason more flexible

2026-08-23T12:20:06+00:00

[ Upstream commit 54a59aed395ce0f4177b5212e5746a6462de3ad9 ]

Currently, the kfree_skb_reason() in sch_handle_{ingress,egress}() can only
express a basic SKB_DROP_REASON_TC_INGRESS or SKB_DROP_REASON_TC_EGRESS reason.

Victor kicked-off an initial proposal to make this more flexible by disambiguating
verdict from return code by moving the verdict into struct tcf_result and
letting tcf_classify() return a negative error. If hit, then two new drop
reasons were added in the proposal, that is SKB_DROP_REASON_TC_INGRESS_ERROR
as well as SKB_DROP_REASON_TC_EGRESS_ERROR. Further analysis of the actual
error codes would have required to attach to tcf_classify via kprobe/kretprobe
to more deeply debug skb and the returned error.

In order to make the kfree_skb_reason() in sch_handle_{ingress,egress}() more
extensible, it can be addressed in a more straight forward way, that is: Instead
of placing the verdict into struct tcf_result, we can just put the drop reason
in there, which does not require changes throughout various classful schedulers
given the existing verdict logic can stay as is.

Then, SKB_DROP_REASON_TC_ERROR{,_*} can be added to the enum skb_drop_reason
to disambiguate between an error or an intentional drop. New drop reason error
codes can be added successively to the tc code base.

For internal error locations which have not yet been annotated with a
SKB_DROP_REASON_TC_ERROR{,_*}, the fallback is SKB_DROP_REASON_TC_INGRESS and
SKB_DROP_REASON_TC_EGRESS, respectively. Generic errors could be marked with a
SKB_DROP_REASON_TC_ERROR code until they are converted to more specific ones
if it is found that they would be useful for troubleshooting.

While drop reasons have infrastructure for subsystem specific error codes which
are currently used by mac80211 and ovs, Jakub mentioned that it is preferred
for tc to use the enum skb_drop_reason core codes given it is a better fit and
currently the tooling support is better, too.

With regards to the latter:

  [...] I think Alastair (bpftrace) is working on auto-prettifying enums when
  bpftrace outputs maps. So we can do something like:

  $ bpftrace -e 'tracepoint:skb:kfree_skb { @[args->reason] = count(); }'
  Attaching 1 probe...
  ^C

  @[SKB_DROP_REASON_TC_INGRESS]: 2
  @[SKB_CONSUMED]: 34

  ^^^^^^^^^^^^ names!!

  Auto-magically. [...]

Add a small helper tcf_set_drop_reason() which can be used to set the drop reason
into the tcf_result.

Signed-off-by: Daniel Borkmann 
Cc: Jamal Hadi Salim 
Cc: Victor Nogueira 
Link: https://lore.kernel.org/netdev/20231006063233.74345d36@kernel.org
Reviewed-by: Jakub Kicinski 
Link: https://lore.kernel.org/r/20231009092655.22025-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski 
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin

net: pktgen: fix proc entry use-after-free

2026-08-23T12:20:03+00:00

[ Upstream commit 817ff6efdb7f484ea547218e11e17d8e43daa3b4 ]

pktgen_change_name() replaces pkt_dev->entry while holding t->if_lock.
pktgen_remove_device() removes the same entry before
_rem_dev_from_if_list() takes that lock.

This allows the following interleaving:

  CPU 0 (NETDEV_CHANGENAME)       CPU 1 (kpktgend)
  if_lock(t)
  proc_remove(pkt_dev->entry)
                                  proc_remove(pkt_dev->entry)
  pkt_dev->entry = proc_create_data(...)
  if_unlock(t)

The kthread can pass the stale proc_dir_entry to proc_remove() after the
rename path has freed it. A reproducer with a widened race window reports:

  BUG: KASAN: slab-use-after-free in proc_remove+0x78/0x80
  Read of size 8 at addr ffff8881478fea70 by task kpktgend_0/67
  Call Trace:
   proc_remove+0x78/0x80
   pktgen_remove_device.isra.0+0x11c/0x4c0
   pktgen_thread_worker+0x1214/0x6bc0
   kthread+0x2c6/0x3b0
  Allocated by task 95:
   __proc_create+0x204/0x790
   proc_create_data+0x72/0xe0
   pktgen_thread_write+0xd61/0x1510
  Freed by task 28:
   kmem_cache_free+0xcb/0x3d0
   proc_free_inode+0x5b/0x80
   rcu_core+0x50a/0x1850
  The buggy address belongs to the object at ffff8881478fea00
   which belongs to the cache proc_dir_entry of size 192

Move proc_remove() into the if_lock-protected list removal helper. Keep it
before list_del_rcu() to preserve the ordering required by add_device().
The rename path must then finish replacing the entry before removal, or
it observes that the device is no longer on the list.

Fixes: 39df232f1a9b ("[PKTGEN]: fix device name handling")
Cc: stable@vger.kernel.org
Signed-off-by: Chengfeng Ye 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20260719145740.2888967-1-nicoyip.dev@gmail.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

net: pktgen: fix code style (WARNING: Block comments)

2026-08-23T12:20:03+00:00

[ Upstream commit 870b856cb478bc02fffe4d89897e62c692efb09a ]

Fix checkpatch code style warnings:

  WARNING: Block comments use a trailing */ on a separate line
  +                                * removal by worker thread */

  WARNING: Block comments use * on subsequent lines
  +       __u8 tos;            /* six MSB of (former) IPv4 TOS
  +                               are for dscp codepoint */

  WARNING: Block comments use a trailing */ on a separate line
  +                               are for dscp codepoint */

  WARNING: Block comments use * on subsequent lines
  +       __u8 traffic_class;  /* ditto for the (former) Traffic Class in IPv6
  +                               (see RFC 3260, sec. 4) */

  WARNING: Block comments use a trailing */ on a separate line
  +                               (see RFC 3260, sec. 4) */

  WARNING: Block comments use * on subsequent lines
  +       /* = {
  +          0x00, 0x80, 0xC8, 0x79, 0xB3, 0xCB,

  WARNING: Block comments use * on subsequent lines
  +       /* Field for thread to receive "posted" events terminate,
  +          stop ifs etc. */

  WARNING: Block comments use a trailing */ on a separate line
  +          stop ifs etc. */

  WARNING: Block comments should align the * on each line
  + * we go look for it ...
  +*/

  WARNING: Block comments use a trailing */ on a separate line
  +        * we resolve the dst issue */

  WARNING: Block comments use a trailing */ on a separate line
  +        * with proc_create_data() */

Signed-off-by: Peter Seiderer 
Reviewed-by: Toke Høiland-Jørgensen 
Signed-off-by: Jakub Kicinski 
Stable-dep-of: 817ff6efdb7f ("net: pktgen: fix proc entry use-after-free")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

net: gro: fix double aggregation of flush-marked skbs

2026-08-23T12:20:01+00:00

[ Upstream commit e751256486d0ded20f5a9f9863467f1dce65142f ]

Commit 0ab03f353d36 ("net-gro: Fix GRO flush when receiving a GSO
packet.") added a flush check to skb_gro_receive(), but
skb_gro_receive_list() lacks the same validation.

As a result, packets marked with NAPI_GRO_CB(skb)->flush may still be
re-aggregated.

This allows already-GRO'd packets with existing frag_list to be
re-aggregated into a new GRO session, corrupting the frag_list chain
structure. When skb_segment() attempts to unpack these malformed packets,
it encounters invalid state and triggers a kernel panic.

Scenario (Tethering/Device forwarding):
  1. Driver: Generated aggregated packet P1 via LRO with frag_list
  2. Dev A: Receives aggregated fraglist packet and flush flag set
  3. Dev A: Re-enters GRO, skb_gro_receive_list() is called
  4. Missing flush check allows re-aggregation despite flush flag
  5. Frag_list chain becomes corrupted (loops or dangling refs)
  6. Dev B: TX path calls skb_segment(), crashes on corrupted frag_list

Root cause in skb_segment():
  The check at line ~4891:
    if (hsize <= 0 && i >= nfrags && skb_headlen(list_skb) &&
        (skb_headlen(list_skb) == len || sg)) {

  When frag_list is corrupted by double aggregation, when list_skb is
  a NULL pointer from skb->next, skb_headlen(list_skb) dereference
  NULL/corrupted pointers occurs.

Call Trace:
 skb_headlen(NULL skb)
 skb_segment
 tcp_gso_segment
 tcp4_gso_segment
 inet_gso_segment
 skb_mac_gso_segment
 __skb_gso_segment
 skb_gso_segment
 validate_xmit_skb
 validate_xmit_skb_list
 sch_direct_xmit
 qdisc_restart
 __qdisc_run
 qdisc_run
 net_tx_action

Fix: Add NAPI_GRO_CB(skb)->flush validation to the early-return check in
skb_gro_receive_list(), matching the defensive programming pattern of
skb_gro_receive().

Fixes: 3a1296a38d0c ("net: Support GRO/GSO fraglist chaining.")
Cc: stable@vger.kernel.org
Signed-off-by: Shiming Cheng 
Reviewed-by: Willem de Bruijn 
Link: https://patch.msgid.link/20260709014704.3625-1-shiming.cheng@mediatek.com
Signed-off-by: Jakub Kicinski 
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

net: move skb_gro_receive_list from udp to core

2026-08-23T12:20:01+00:00

[ Upstream commit 8928756d53d5b99dcd18073dc7738b8ebdbe7d96 ]

This helper function will be used for TCP fraglist GRO support

Acked-by: Paolo Abeni 
Reviewed-by: Eric Dumazet 
Signed-off-by: Felix Fietkau 
Reviewed-by: David Ahern 
Reviewed-by: Willem de Bruijn 
Signed-off-by: Paolo Abeni 
Stable-dep-of: e751256486d0 ("net: gro: fix double aggregation of flush-marked skbs")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

xdp: reject clones that overrun skb_shared_info tailroom

2026-08-19T16:13:13+00:00

commit e48e8edbef2eb824201495daa5234560f632b23c upstream.

xdpf_clone() clones broadcast copies into a single page and sets
frame_sz to PAGE_SIZE. __xdp_build_skb_from_frame() later treats that
page like a normal XDP frame and expects the usual skb_shared_info
tailroom at the end of the buffer.

The current check only rejects frames whose linear xdp_frame header,
headroom, and packet data exceed PAGE_SIZE. A source frame backed by a
larger allocation can still satisfy that check while extending into the
clone's required shared-info area. When such a clone is converted back
into an skb, build_skb_around() places skb_shared_info over live packet
bytes and later writes can corrupt XDP return metadata.

Reject clones unless their linear area fits inside
SKB_WITH_OVERHEAD(PAGE_SIZE), matching the tailroom requirement already
enforced by the XDP-to-skb conversion path.

Fixes: e624d4ed4aa8 ("xdp: Extend xdp_redirect_map with broadcast support")
Cc: stable@vger.kernel.org
Reported-by: Vega 
Signed-off-by: Zhiling Zou 
Link: https://patch.msgid.link/6b2afef5d1738763c6965e8e466eb16e43e4f956.1785757386.git.zhilinz@nebusec.ai
Signed-off-by: Jakub Kicinski 
Signed-off-by: Greg Kroah-Hartman

net: remove WARN_ON_ONCE() from sk_mc_loop()

2026-08-19T16:13:08+00:00

[ Upstream commit b8a39a09ae4eaae04309e1e38ed6a1101d967496 ]

sk_mc_loop() can be called for sockets that are neither AF_INET
nor AF_INET6 (e.g. AF_PACKET sockets when sending packets via raw/packet
socket over virtual devices such as VRF or ipvlan).

In such cases, sk_family is not AF_INET/AF_INET6 and sk_mc_loop() falls
through the switch statement and triggers WARN_ON_ONCE(1).

Non-INET sockets do not support IP_MULTICAST_LOOP or IPV6_MULTICAST_LOOP
options, so loopback should default to true without generating a warning.

Fixes: f60e5990d9c1 ("ipv6: protect skb->sk accesses from recursive dereference inside the stack")
Reported-by: syzbot+22c3218a6fa219e47321@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6a72024c.13623e66.bdc14.0019.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet 
Link: https://patch.msgid.link/20260804152048.2134341-1-edumazet@google.com
Signed-off-by: Paolo Abeni 
Signed-off-by: Sasha Levin

net: sched: refine software bypass handling in tc_run

2026-08-19T16:13:07+00:00

[ Upstream commit a12c76a03386e32413ae8eaaefa337e491880632 ]

This patch addresses issues with filter counting in block (tcf_block),
particularly for software bypass scenarios, by introducing a more
accurate mechanism using useswcnt.

Previously, filtercnt and skipswcnt were introduced by:

  Commit 2081fd3445fe ("net: sched: cls_api: add filter counter") and
  Commit f631ef39d819 ("net: sched: cls_api: add skip_sw counter")

  filtercnt tracked all tp (tcf_proto) objects added to a block, and
  skipswcnt counted tp objects with the skipsw attribute set.

The problem is: a single tp can contain multiple filters, some with skipsw
and others without. The current implementation fails in the case:

  When the first filter in a tp has skipsw, both skipswcnt and filtercnt
  are incremented, then adding a second filter without skipsw to the same
  tp does not modify these counters because tp->counted is already set.

  This results in bypass software behavior based solely on skipswcnt
  equaling filtercnt, even when the block includes filters without
  skipsw. Consequently, filters without skipsw are inadvertently bypassed.

To address this, the patch introduces useswcnt in block to explicitly count
tp objects containing at least one filter without skipsw. Key changes
include:

  Whenever a filter without skipsw is added, its tp is marked with usesw
  and counted in useswcnt. tc_run() now uses useswcnt to determine software
  bypass, eliminating reliance on filtercnt and skipswcnt.

  This refined approach prevents software bypass for blocks containing
  mixed filters, ensuring correct behavior in tc_run().

Additionally, as atomic operations on useswcnt ensure thread safety and
tp->lock guards access to tp->usesw and tp->counted, the broader lock
down_write(&block->cb_lock) is no longer required in tc_new_tfilter(),
and this resolves a performance regression caused by the filter counting
mechanism during parallel filter insertions.

  The improvement can be demonstrated using the following script:

  # cat insert_tc_rules.sh

    tc qdisc add dev ens1f0np0 ingress
    for i in $(seq 16); do
        taskset -c $i tc -b rules_$i.txt &
    done
    wait

  Each of rules_$i.txt files above includes 100000 tc filter rules to a
  mlx5 driver NIC ens1f0np0.

  Without this patch:

  # time sh insert_tc_rules.sh

    real    0m50.780s
    user    0m23.556s
    sys	    4m13.032s

  With this patch:

  # time sh insert_tc_rules.sh

    real    0m17.718s
    user    0m7.807s
    sys     3m45.050s

Fixes: 047f340b36fc ("net: sched: make skip_sw actually skip software")
Reported-by: Shuang Li 
Signed-off-by: Xin Long 
Acked-by: Marcelo Ricardo Leitner 
Reviewed-by: Asbjørn Sloth Tønnesen 
Tested-by: Asbjørn Sloth Tønnesen 
Signed-off-by: David S. Miller 
Stable-dep-of: a347304b2ca1 ("net/sched: cls_api: Always acquire rtnl_lock when destroying locked classifiers")
Signed-off-by: Sasha Levin