linux-stable.git/net, branch v6.6.153 Linux kernel stable tree net: harmonize tstats and dstats 2026-08-23T12:20:07+00:00 Paolo Abeni pabeni@redhat.com 2025-02-01T18:02:51+00:00 171f95d6628633c2e11111f88c9db6f401901ffa 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: <BROADCAST,MULTICAST,UP,LOWER_UP> 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 <pabeni@redhat.com> Reviewed-by: Guillaume Nault <gnault@redhat.com> Link: https://patch.msgid.link/2e1c444cf0f63ae472baff29862c4c869be17031.1738432804.git.pabeni@redhat.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
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: <BROADCAST,MULTICAST,UP,LOWER_UP> 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 <pabeni@redhat.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Link: https://patch.msgid.link/2e1c444cf0f63ae472baff29862c4c869be17031.1738432804.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/x25: fix use-after-free of the socket by its timers 2026-08-23T12:20:07+00:00 Baul Lee baul.lee@xbow.com 2026-07-26T22:03:42+00:00 1fc9f6d2c7c9fdb341bfe8ca449c990632299ea6 commit 2195424c3da2ef1829a63b807e3a900a90e57d85 upstream. The x25 timers are armed with mod_timer() and cancelled with timer_delete(), so a pending timer holds no reference on the socket and a cancel does not wait for a callback already running on another CPU. x25_heartbeat_expiry() also rearms unconditionally, so it can reinstall sk->sk_timer after __x25_destroy_socket() has passed its cancel point. The following __sock_put() frees the socket while the timer is still queued, and the next expiry uses freed memory. KASAN reports a slab-use-after-free on the kmalloc-2k object freed by close(). timer_delete_sync() cannot be used here: x25_heartbeat_expiry() and x25_timer_expiry() both reach the cancels from inside the timer they would wait on, through __x25_destroy_socket() and x25_disconnect(). Arm the timers with sk_reset_timer() and cancel them with sk_stop_timer() so that an armed timer owns a reference, and release it in both expiry handlers. Rearm the heartbeat only while sk_hashed(sk) is still true, since __x25_destroy_socket() unlinks the socket before dropping it. Arm the deferred destroy timer the same way and drop its reference in x25_destroy_timer(). Reproduced on net with KASAN, with the heartbeat period shortened so the window recurs. With this patch the reproducer no longer triggers a report and /proc/net/x25 drains. Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Signed-off-by: Baul Lee <baul.lee@xbow.com> Link: https://patch.msgid.link/20260726220342.47245-1-baul.lee@xbow.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> [ adjusted context due to `del_timer()` not yet renamed to `timer_delete()` ] Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> 
commit 2195424c3da2ef1829a63b807e3a900a90e57d85 upstream.

The x25 timers are armed with mod_timer() and cancelled with
timer_delete(), so a pending timer holds no reference on the socket and a
cancel does not wait for a callback already running on another CPU.

x25_heartbeat_expiry() also rearms unconditionally, so it can reinstall
sk->sk_timer after __x25_destroy_socket() has passed its cancel point.
The following __sock_put() frees the socket while the timer is still
queued, and the next expiry uses freed memory.  KASAN reports a
slab-use-after-free on the kmalloc-2k object freed by close().

timer_delete_sync() cannot be used here: x25_heartbeat_expiry() and
x25_timer_expiry() both reach the cancels from inside the timer they
would wait on, through __x25_destroy_socket() and x25_disconnect().

Arm the timers with sk_reset_timer() and cancel them with sk_stop_timer()
so that an armed timer owns a reference, and release it in both expiry
handlers.  Rearm the heartbeat only while sk_hashed(sk) is still true,
since __x25_destroy_socket() unlinks the socket before dropping it.  Arm
the deferred destroy timer the same way and drop its reference in
x25_destroy_timer().

Reproduced on net with KASAN, with the heartbeat period shortened so the
window recurs.  With this patch the reproducer no longer triggers a
report and /proc/net/x25 drains.

Discovered by XBOW, triaged by Baul Lee <baul.lee@xbow.com>

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Baul Lee <baul.lee@xbow.com>
Link: https://patch.msgid.link/20260726220342.47245-1-baul.lee@xbow.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ adjusted context due to `del_timer()` not yet renamed to `timer_delete()` ]
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/sched: cls_bpf: reject dev-bound programs bound to a different device 2026-08-23T12:20:07+00:00 Jamal Hadi Salim jhs@mojatatu.com 2026-08-09T09:44:18+00:00 ec5a552f4b2d841c6c021752450716e1a9676661 [ Upstream commit 120977e2c096deea4e866e4273be9220b957c29e ] cls_bpf_prog_from_efd() obtained a SCHED_CLS program via bpf_prog_get_type_dev() but never verified that a device-bound (offloaded) program's bound netdev matches the TC netdev the classifier is being attached to. This let a program loaded with prog_ifindex for device A be attached via cls_bpf + skip_sw to device B; deleting device A then destroyed the program's offload state while it was still attached to device B, triggering a netdevsim WARN (panic with panic_on_warn=1). Mirror the XDP attach path (net/core/dev.c) and reject the attach with -EINVAL when a dev-bound program's bound device does not match the target device. Fixes: 2b3486bc2d23 ("bpf: Introduce device-bound XDP programs") Reported-by: vega@nebusec.ai Tested-by: Victor Nogueira <victor@mojatatu.com> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Link: https://patch.msgid.link/20260809094418.901607-1-jhs@mojatatu.com Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 120977e2c096deea4e866e4273be9220b957c29e ]

cls_bpf_prog_from_efd() obtained a SCHED_CLS program via
bpf_prog_get_type_dev() but never verified that a device-bound (offloaded)
program's bound netdev matches the TC netdev the classifier is being
attached to. This let a program loaded with prog_ifindex for device A be
attached via cls_bpf + skip_sw to device B; deleting device A then
destroyed the program's offload state while it was still attached to
device B, triggering a netdevsim WARN (panic with panic_on_warn=1).

Mirror the XDP attach path (net/core/dev.c) and reject the attach with
-EINVAL when a dev-bound program's bound device does not match the
target device.

Fixes: 2b3486bc2d23 ("bpf: Introduce device-bound XDP programs")
Reported-by: vega@nebusec.ai
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://patch.msgid.link/20260809094418.901607-1-jhs@mojatatu.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
net/sched: cls_u32: skip hash tables in u32_bind_class() 2026-08-23T12:20:06+00:00 Zhang Changzhong zhangchangzhong@huawei.com 2026-08-07T07:50:38+00:00 19d114b93c94bdef70496f26685c2a6b242f41b3 [ Upstream commit 6d3724e616faf952c3adcf8414fc21a828ef3709 ] u32_walk() enumerates both struct tc_u_hnode and struct tc_u_knode through the walker callback. u32_bind_class() unconditionally casts the passed fh to tc_u_knode and accesses &n->res, so when fh is actually a tc_u_hnode, which has no tcf_result member, this results in a slab-out-of-bounds read of res->classid in tc_cls_bind_class(). The issue can be reproduced with the following commands: tc qdisc add dev lo root handle 1: hfsc tc class add dev lo parent 1: classid 1:1 hfsc sc rate 1000kbit tc filter add dev lo parent 1:1 protocol ip prio 1 u32 match u32 0 0 flowid 1:1 tc class add dev lo parent 1: classid 1:2 hfsc sc rate 2000kbit Fix this by skipping hash tables via the TC_U32_KEY(handle) check. Fixes: 07d79fc7d94e ("net_sched: add reverse binding for tc class") Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com> Acked-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://patch.msgid.link/1786089038-36366-1-git-send-email-zhangchangzhong@huawei.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 6d3724e616faf952c3adcf8414fc21a828ef3709 ]

u32_walk() enumerates both struct tc_u_hnode and struct tc_u_knode
through the walker callback. u32_bind_class() unconditionally casts the
passed fh to tc_u_knode and accesses &n->res, so when fh is actually a
tc_u_hnode, which has no tcf_result member, this results in a
slab-out-of-bounds read of res->classid in tc_cls_bind_class().

The issue can be reproduced with the following commands:

    tc qdisc add dev lo root handle 1: hfsc
    tc class add dev lo parent 1: classid 1:1 hfsc sc rate 1000kbit
    tc filter add dev lo parent 1:1 protocol ip prio 1 u32 match u32 0 0 flowid 1:1
    tc class add dev lo parent 1: classid 1:2 hfsc sc rate 2000kbit

Fix this by skipping hash tables via the TC_U32_KEY(handle) check.

Fixes: 07d79fc7d94e ("net_sched: add reverse binding for tc class")
Signed-off-by: Zhang Changzhong <zhangchangzhong@huawei.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://patch.msgid.link/1786089038-36366-1-git-send-email-zhangchangzhong@huawei.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain 2026-08-23T12:20:06+00:00 Jamal Hadi Salim jhs@mojatatu.com 2026-08-09T09:09:28+00:00 91d55fd1fdb85c8371ca8793c788ea7d5192383a [ Upstream commit f60b396ee174206fe08ebf997d16cd3801b77b22 ] tcf_action_exec() handles TC_ACT_GOTO_CHAIN by first checking rcu_access_pointer(a->goto_chain) and then calling tcf_action_goto_chain_exec(), which does a second, independent rcu_dereference_bh(a->goto_chain) read and immediately dereferences chain->filter_chain. A concurrent tcf_action_set_ctrlact() (e.g. the gact replace path) can clear a->goto_chain between the two reads, so the second read returns NULL and tcf_action_goto_chain_exec() dereferences NULL. Fix the race by doing a single rcu_dereference_bh() read of a->goto_chain in tcf_action_exec(), checking it once for NULL, and passing the resulting chain pointer into tcf_action_goto_chain_exec(). This turns the split check/use into a single check/use on one value. Fixes: ee3bbfe806cd ("net/sched: let actions use RCU to access 'goto_chain'") Reported-by: vega@nebusec.ai Tested-by: Victor Nogueira <victor@mojatatu.com> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com> Reviewed-by: Davide Caratti <dcaratti@redhat.com> Link: https://patch.msgid.link/20260809090928.868186-1-jhs@mojatatu.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit f60b396ee174206fe08ebf997d16cd3801b77b22 ]

tcf_action_exec() handles TC_ACT_GOTO_CHAIN by first checking
rcu_access_pointer(a->goto_chain) and then calling
tcf_action_goto_chain_exec(), which does a second, independent
rcu_dereference_bh(a->goto_chain) read and immediately dereferences
chain->filter_chain. A concurrent tcf_action_set_ctrlact() (e.g. the gact
replace path) can clear a->goto_chain between the two reads, so the second
read returns NULL and tcf_action_goto_chain_exec() dereferences NULL.

Fix the race by doing a single rcu_dereference_bh() read of a->goto_chain
in tcf_action_exec(), checking it once for NULL, and passing the resulting
chain pointer into tcf_action_goto_chain_exec(). This turns the split
check/use into a single check/use on one value.

Fixes: ee3bbfe806cd ("net/sched: let actions use RCU to access 'goto_chain'")
Reported-by: vega@nebusec.ai
Tested-by: Victor Nogueira <victor@mojatatu.com>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Reviewed-by: Davide Caratti <dcaratti@redhat.com>
Link: https://patch.msgid.link/20260809090928.868186-1-jhs@mojatatu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
net: sched: Add initial TC error skb drop reasons 2026-08-23T12:20:06+00:00 Victor Nogueira victor@mojatatu.com 2023-12-16T20:44:36+00:00 a857e3408be07aa1e388cac331a263704b5200c8 [ Upstream commit 4cf24dc8934074725042c0bd10b91f4d4b5269bb ] Continue expanding Daniel's patch by adding new skb drop reasons that are idiosyncratic to TC. More specifically: - SKB_DROP_REASON_TC_COOKIE_ERROR: An error occurred whilst processing a tc ext cookie. - SKB_DROP_REASON_TC_CHAIN_NOTFOUND: tc chain lookup failed. - SKB_DROP_REASON_TC_RECLASSIFY_LOOP: tc exceeded max reclassify loop iterations Signed-off-by: Victor Nogueira <victor@mojatatu.com> Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 4cf24dc8934074725042c0bd10b91f4d4b5269bb ]

Continue expanding Daniel's patch by adding new skb drop reasons that
are idiosyncratic to TC.

More specifically:

- SKB_DROP_REASON_TC_COOKIE_ERROR: An error occurred whilst
  processing a tc ext cookie.

- SKB_DROP_REASON_TC_CHAIN_NOTFOUND: tc chain lookup failed.

- SKB_DROP_REASON_TC_RECLASSIFY_LOOP: tc exceeded max reclassify loop
  iterations

Signed-off-by: Victor Nogueira <victor@mojatatu.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin <sashal@kernel.org>
net: sched: Move drop_reason to struct tc_skb_cb 2026-08-23T12:20:06+00:00 Victor Nogueira victor@mojatatu.com 2023-12-16T20:44:34+00:00 d54e7ec85166484e50efffa741f3b540ad28907b [ 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 <victor@mojatatu.com> Acked-by: Daniel Borkmann <daniel@iogearbox.net> Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ 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 <victor@mojatatu.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin <sashal@kernel.org>
packet: add a generic drop reason for receive 2026-08-23T12:20:06+00:00 Yan Zhai yan@cloudflare.com 2023-12-04T19:33:28+00:00 14f679a8d2ddc7835cdfb77edd2e8a0eb62f81c7 [ Upstream commit 2f57dd94bdef083855366138646b26b05f410d99 ] Commit da37845fdce2 ("packet: uses kfree_skb() for errors.") switches from consume_skb to kfree_skb to improve error handling. However, this could bring a lot of noises when we monitor real packet drops in kfree_skb[1], because in tpacket_rcv or packet_rcv only packet clones can be freed, not actual packets. Adding a generic drop reason to allow distinguish these "clone drops". [1]: https://lore.kernel.org/netdev/CABWYdi00L+O30Q=Zah28QwZ_5RU-xcxLFUK2Zj08A8MrLk9jzg@mail.gmail.com/ Fixes: da37845fdce2 ("packet: uses kfree_skb() for errors.") Suggested-by: Eric Dumazet <edumazet@google.com> Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com> Signed-off-by: Yan Zhai <yan@cloudflare.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Link: https://lore.kernel.org/r/ZW4piNbx3IenYnuw@debian.debian Signed-off-by: Jakub Kicinski <kuba@kernel.org> Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 2f57dd94bdef083855366138646b26b05f410d99 ]

Commit da37845fdce2 ("packet: uses kfree_skb() for errors.") switches
from consume_skb to kfree_skb to improve error handling. However, this
could bring a lot of noises when we monitor real packet drops in
kfree_skb[1], because in tpacket_rcv or packet_rcv only packet clones
can be freed, not actual packets.

Adding a generic drop reason to allow distinguish these "clone drops".

[1]: https://lore.kernel.org/netdev/CABWYdi00L+O30Q=Zah28QwZ_5RU-xcxLFUK2Zj08A8MrLk9jzg@mail.gmail.com/
Fixes: da37845fdce2 ("packet: uses kfree_skb() for errors.")
Suggested-by: Eric Dumazet <edumazet@google.com>
Suggested-by: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Signed-off-by: Yan Zhai <yan@cloudflare.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://lore.kernel.org/r/ZW4piNbx3IenYnuw@debian.debian
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin <sashal@kernel.org>
net, sched: Fix SKB_NOT_DROPPED_YET splat under debug config 2026-08-23T12:20:06+00:00 Jamal Hadi Salim jhs@mojatatu.com 2023-10-28T17:16:10+00:00 b72e44dc038f25779926f26d8826a97345032b14 [ Upstream commit 40cb2fdfed342e7e578d551a073687789f698d89 ] Getting the following splat [1] with CONFIG_DEBUG_NET=y and this reproducer [2]. Problem seems to be that classifiers clear 'struct tcf_result::drop_reason', thereby triggering the warning in __kfree_skb_reason() due to reason being 'SKB_NOT_DROPPED_YET' (0). Fixed by disambiguating a legit error from a verdict with a bogus drop_reason [1] WARNING: CPU: 0 PID: 181 at net/core/skbuff.c:1082 kfree_skb_reason+0x38/0x130 Modules linked in: CPU: 0 PID: 181 Comm: mausezahn Not tainted 6.6.0-rc6-custom-ge43e6d9582e0 #682 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc37 04/01/2014 RIP: 0010:kfree_skb_reason+0x38/0x130 [...] Call Trace: <IRQ> __netif_receive_skb_core.constprop.0+0x837/0xdb0 __netif_receive_skb_one_core+0x3c/0x70 process_backlog+0x95/0x130 __napi_poll+0x25/0x1b0 net_rx_action+0x29b/0x310 __do_softirq+0xc0/0x29b do_softirq+0x43/0x60 </IRQ> [2] ip link add name veth0 type veth peer name veth1 ip link set dev veth0 up ip link set dev veth1 up tc qdisc add dev veth1 clsact tc filter add dev veth1 ingress pref 1 proto all flower dst_mac 00:11:22:33:44:55 action drop mausezahn veth0 -a own -b 00:11:22:33:44:55 -q -c 1 Ido reported: [...] getting the following splat [1] with CONFIG_DEBUG_NET=y and this reproducer [2]. Problem seems to be that classifiers clear 'struct tcf_result::drop_reason', thereby triggering the warning in __kfree_skb_reason() due to reason being 'SKB_NOT_DROPPED_YET' (0). [...] [1] WARNING: CPU: 0 PID: 181 at net/core/skbuff.c:1082 kfree_skb_reason+0x38/0x130 Modules linked in: CPU: 0 PID: 181 Comm: mausezahn Not tainted 6.6.0-rc6-custom-ge43e6d9582e0 #682 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc37 04/01/2014 RIP: 0010:kfree_skb_reason+0x38/0x130 [...] Call Trace: <IRQ> __netif_receive_skb_core.constprop.0+0x837/0xdb0 __netif_receive_skb_one_core+0x3c/0x70 process_backlog+0x95/0x130 __napi_poll+0x25/0x1b0 net_rx_action+0x29b/0x310 __do_softirq+0xc0/0x29b do_softirq+0x43/0x60 </IRQ> [2] #!/bin/bash ip link add name veth0 type veth peer name veth1 ip link set dev veth0 up ip link set dev veth1 up tc qdisc add dev veth1 clsact tc filter add dev veth1 ingress pref 1 proto all flower dst_mac 00:11:22:33:44:55 action drop mausezahn veth0 -a own -b 00:11:22:33:44:55 -q -c 1 What happens is that inside most classifiers the tcf_result is copied over from a filter template e.g. *res = f->res which then implicitly overrides the prior SKB_DROP_REASON_TC_{INGRESS,EGRESS} default drop code which was set via sch_handle_{ingress,egress}() for kfree_skb_reason(). Commit text above copied verbatim from Daniel. The general idea of the patch is not very different from what Ido originally posted but instead done at the cls_api codepath. Fixes: 54a59aed395c ("net, sched: Make tc-related drop reason more flexible") Reported-by: Ido Schimmel <idosch@idosch.org> Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://lore.kernel.org/netdev/ZTjY959R+AFXf3Xy@shredder Reviewed-by: Simon Horman <horms@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net> Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 40cb2fdfed342e7e578d551a073687789f698d89 ]

Getting the following splat [1] with CONFIG_DEBUG_NET=y and this
reproducer [2]. Problem seems to be that classifiers clear 'struct
tcf_result::drop_reason', thereby triggering the warning in
__kfree_skb_reason() due to reason being 'SKB_NOT_DROPPED_YET' (0).

Fixed by disambiguating a legit error from a verdict with a bogus drop_reason

[1]
WARNING: CPU: 0 PID: 181 at net/core/skbuff.c:1082 kfree_skb_reason+0x38/0x130
Modules linked in:
CPU: 0 PID: 181 Comm: mausezahn Not tainted 6.6.0-rc6-custom-ge43e6d9582e0 #682
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc37 04/01/2014
RIP: 0010:kfree_skb_reason+0x38/0x130
[...]
Call Trace:
 <IRQ>
 __netif_receive_skb_core.constprop.0+0x837/0xdb0
 __netif_receive_skb_one_core+0x3c/0x70
 process_backlog+0x95/0x130
 __napi_poll+0x25/0x1b0
 net_rx_action+0x29b/0x310
 __do_softirq+0xc0/0x29b
 do_softirq+0x43/0x60
 </IRQ>

[2]

ip link add name veth0 type veth peer name veth1
ip link set dev veth0 up
ip link set dev veth1 up
tc qdisc add dev veth1 clsact
tc filter add dev veth1 ingress pref 1 proto all flower dst_mac 00:11:22:33:44:55 action drop
mausezahn veth0 -a own -b 00:11:22:33:44:55 -q -c 1

Ido reported:

  [...] getting the following splat [1] with CONFIG_DEBUG_NET=y and this
  reproducer [2]. Problem seems to be that classifiers clear 'struct
  tcf_result::drop_reason', thereby triggering the warning in
  __kfree_skb_reason() due to reason being 'SKB_NOT_DROPPED_YET' (0). [...]

  [1]
  WARNING: CPU: 0 PID: 181 at net/core/skbuff.c:1082 kfree_skb_reason+0x38/0x130
  Modules linked in:
  CPU: 0 PID: 181 Comm: mausezahn Not tainted 6.6.0-rc6-custom-ge43e6d9582e0 #682
  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-1.fc37 04/01/2014
  RIP: 0010:kfree_skb_reason+0x38/0x130
  [...]
  Call Trace:
   <IRQ>
   __netif_receive_skb_core.constprop.0+0x837/0xdb0
   __netif_receive_skb_one_core+0x3c/0x70
   process_backlog+0x95/0x130
   __napi_poll+0x25/0x1b0
   net_rx_action+0x29b/0x310
   __do_softirq+0xc0/0x29b
   do_softirq+0x43/0x60
   </IRQ>

  [2]
  #!/bin/bash

  ip link add name veth0 type veth peer name veth1
  ip link set dev veth0 up
  ip link set dev veth1 up
  tc qdisc add dev veth1 clsact
  tc filter add dev veth1 ingress pref 1 proto all flower dst_mac 00:11:22:33:44:55 action drop
  mausezahn veth0 -a own -b 00:11:22:33:44:55 -q -c 1

What happens is that inside most classifiers the tcf_result is copied over
from a filter template e.g. *res = f->res which then implicitly overrides
the prior SKB_DROP_REASON_TC_{INGRESS,EGRESS} default drop code which was
set via sch_handle_{ingress,egress}() for kfree_skb_reason().

Commit text above copied verbatim from Daniel. The general idea of the patch
is not very different from what Ido originally posted but instead done at the
cls_api codepath.

Fixes: 54a59aed395c ("net, sched: Make tc-related drop reason more flexible")
Reported-by: Ido Schimmel <idosch@idosch.org>
Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Link: https://lore.kernel.org/netdev/ZTjY959R+AFXf3Xy@shredder
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin <sashal@kernel.org>
net, sched: Add tcf_set_drop_reason for {__,}tcf_classify 2026-08-23T12:20:06+00:00 Daniel Borkmann daniel@iogearbox.net 2023-10-09T09:26:55+00:00 69c66cf557906354a4d4b1f6103790a850b84120 [ Upstream commit 39d08b91646d83e87f7cbcd846b3ef33b1a53b79 ] Add an initial user for the newly added tcf_set_drop_reason() helper to set the drop reason for internal errors leading to TC_ACT_SHOT inside {__,}tcf_classify(). Right now this only adds a very basic SKB_DROP_REASON_TC_ERROR as a generic fallback indicator to mark drop locations. Where needed, such locations can be converted to more specific codes, for example, when hitting the reclassification limit, etc. Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: Victor Nogueira <victor@mojatatu.com> Link: https://lore.kernel.org/r/20231009092655.22025-2-daniel@iogearbox.net Signed-off-by: Jakub Kicinski <kuba@kernel.org> Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain") Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 39d08b91646d83e87f7cbcd846b3ef33b1a53b79 ]

Add an initial user for the newly added tcf_set_drop_reason() helper to set the
drop reason for internal errors leading to TC_ACT_SHOT inside {__,}tcf_classify().

Right now this only adds a very basic SKB_DROP_REASON_TC_ERROR as a generic
fallback indicator to mark drop locations. Where needed, such locations can be
converted to more specific codes, for example, when hitting the reclassification
limit, etc.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: Victor Nogueira <victor@mojatatu.com>
Link: https://lore.kernel.org/r/20231009092655.22025-2-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: f60b396ee174 ("net/sched: act_api: fix TOCTOU NULL deref on a->goto_chain")
Signed-off-by: Sasha Levin <sashal@kernel.org>