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linux/net/dsa
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Jakob Unterwurzacher cf3c78ecdf net: dsa: microchip: linearize skb for tail-tagging switches 
[ Upstream commit ba54bce747 ]

The pointer arithmentic for accessing the tail tag only works
for linear skbs.

For nonlinear skbs, it reads uninitialized memory inside the
skb headroom, essentially randomizing the tag. I have observed
it gets set to 6 most of the time.

Example where ksz9477_rcv thinks that the packet from port 1 comes from port 6
(which does not exist for the ksz9896 that's in use), dropping the packet.
Debug prints added by me (not included in this patch):

	[  256.645337] ksz9477_rcv:323 tag0=6
	[  256.645349] skb len=47 headroom=78 headlen=0 tailroom=0
	               mac=(64,14) mac_len=14 net=(78,0) trans=78
	               shinfo(txflags=0 nr_frags=1 gso(size=0 type=0 segs=0))
	               csum(0x0 start=0 offset=0 ip_summed=0 complete_sw=0 valid=0 level=0)
	               hash(0x0 sw=0 l4=0) proto=0x00f8 pkttype=1 iif=3
	               priority=0x0 mark=0x0 alloc_cpu=0 vlan_all=0x0
	               encapsulation=0 inner(proto=0x0000, mac=0, net=0, trans=0)
	[  256.645377] dev name=end1 feat=0x0002e10200114bb3
	[  256.645386] skb headroom: 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
	[  256.645395] skb headroom: 00000010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
	[  256.645403] skb headroom: 00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
	[  256.645411] skb headroom: 00000030: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
	[  256.645420] skb headroom: 00000040: ff ff ff ff ff ff 00 1c 19 f2 e2 db 08 06
	[  256.645428] skb frag:     00000000: 00 01 08 00 06 04 00 01 00 1c 19 f2 e2 db 0a 02
	[  256.645436] skb frag:     00000010: 00 83 00 00 00 00 00 00 0a 02 a0 2f 00 00 00 00
	[  256.645444] skb frag:     00000020: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01
	[  256.645452] ksz_common_rcv:92 dsa_conduit_find_user returned NULL

Call skb_linearize before trying to access the tag.

This patch fixes ksz9477_rcv which is used by the ksz9896 I have at
hand, and also applies the same fix to ksz8795_rcv which seems to have
the same problem.

Signed-off-by: Jakob Unterwurzacher <jakob.unterwurzacher@cherry.de>
CC: stable@vger.kernel.org
Fixes: 016e43a26b ("net: dsa: ksz: Add KSZ8795 tag code")
Fixes: 8b8010fb78 ("dsa: add support for Microchip KSZ tail tagging")
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/20250515072920.2313014-1-jakob.unterwurzacher@cherry.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
History 2025-09-09 18:54:20 +02:00
..
dsa.c net: dsa: allow the DSA master to be seen and changed through rtnetlink 2022-09-20 10:32:35 +02:00
dsa2.c net: dsa: introduce preferred_default_local_cpu_port and use on MT7530 2024-04-27 17:07:17 +02:00
dsa_priv.h net: dsa: make dsa_master_ioctl() see through port_hwtstamp_get() shims 2022-11-14 11:30:49 +00:00
Kconfig net: dsa: tag_ksz: add tag handling for Microchip LAN937x 2022-07-02 16:34:05 +01:00
Makefile net: dsa: allow the DSA master to be seen and changed through rtnetlink 2022-09-20 10:32:35 +02:00
master.c net: dsa: make dsa_master_ioctl() see through port_hwtstamp_get() shims 2022-11-14 11:30:49 +00:00
netlink.c net: dsa: make user ports return to init_net on netns deletion 2022-09-26 11:28:57 -07:00
port.c net: dsa: add support for mac_prepare() and mac_finish() calls 2025-05-02 07:46:50 +02:00
slave.c net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events 2025-02-21 13:50:11 +01:00
switch.c net: dsa: allow masters to join a LAG 2022-09-20 10:32:36 +02:00
tag_8021q.c net: dsa: avoid refcount warnings when ds->ops->tag_8021q_vlan_del() fails 2025-04-25 10:43:51 +02:00
tag_ar9331.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00
tag_brcm.c net: dsa: tag_brcm: legacy: fix pskb_may_pull length 2025-06-27 11:07:17 +01:00
tag_dsa.c net: dsa: tag_dsa: Fix tx from VLAN uppers on non-filtering bridges 2022-03-08 11:12:28 +01:00
tag_gswip.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00
tag_hellcreek.c net: dsa: hellcreek: Check return value 2022-12-02 20:46:52 -08:00
tag_ksz.c net: dsa: microchip: linearize skb for tail-tagging switches 2025-09-09 18:54:20 +02:00
tag_lan9303.c net: dsa: lan9303: handle hwaccel VLAN tags 2022-02-17 09:32:06 -08:00
tag_mtk.c net: dsa: create a helper for locating EtherType DSA headers on TX 2021-08-11 14:44:58 +01:00
tag_ocelot.c net: mscc: ocelot: use ocelot_xmit_get_vlan_info() also for FDMA and register injection 2024-08-29 17:30:43 +02:00
tag_ocelot_8021q.c net: dsa: tag_8021q: merge RX and TX VLANs 2022-02-27 11:06:14 +00:00
tag_qca.c net: dsa: tag_qca: add support for handling mgmt and MIB Ethernet packet 2022-02-02 14:43:59 +00:00
tag_rtl4_a.c net: dsa: tag_rtl4_a: Drop bit 9 from egress frames 2021-09-14 19:34:03 -07:00
tag_rtl8_4.c net: dsa: tag_rtl8_4: fix typo in modalias name 2022-03-09 20:36:24 -08:00
tag_rzn1_a5psw.c net: dsa: add Renesas RZ/N1 switch tag driver 2022-06-27 11:37:55 +01:00
tag_sja1105.c net: dsa: sja1105: always enable the send_meta options 2023-07-19 16:22:06 +02:00
tag_trailer.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00
tag_xrs700x.c net: dsa: remove the struct packet_type argument from dsa_device_ops::rcv() 2021-08-02 15:13:15 +01:00