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linux/net/dsa
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Jakob Unterwurzacher a82c31b8e9 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 18:50:23 +02:00
..
dsa.c Revert "net: dsa: mv88e6xxx: flush switchdev FDB workqueue before removing VLAN" 2022-03-16 14:23:47 +01:00
dsa2.c net: dsa: improve shutdown sequence 2025-01-09 13:28:42 +01:00
dsa_priv.h net: dsa: make dsa_master_ioctl() see through port_hwtstamp_get() shims 2022-11-26 09:24:40 +01:00
Kconfig net: dsa: tag_ocelot_8021q: break circular dependency with ocelot switch lib 2021-10-12 17:35:18 -07:00
Makefile net: dsa: build tag_8021q.c as part of DSA core 2021-07-20 06:36:42 -07:00
master.c net: dsa: make dsa_master_ioctl() see through port_hwtstamp_get() shims 2022-11-26 09:24:40 +01:00
port.c net: dsa: make dsa_master_ioctl() see through port_hwtstamp_get() shims 2022-11-26 09:24:40 +01:00
slave.c net: use eth_hw_addr_set() instead of ether_addr_copy() 2022-08-31 17:16:37 +02:00
switch.c net: dsa: fix incorrect function pointer check for MRP ring roles 2022-01-27 11:03:50 +01:00
tag_8021q.c net: dsa: avoid refcount warnings when ds->ops->tag_8021q_vlan_del() fails 2025-05-02 07:44:11 +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 11:05:17 +01:00
tag_dsa.c net: dsa: mv88e6xxx: isolate the ATU databases of standalone and bridged ports 2021-10-08 15:47:46 -07:00
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 2022-12-14 11:37:25 +01:00
tag_ksz.c net: dsa: microchip: linearize skb for tail-tagging switches 2025-09-09 18:50:23 +02:00
tag_lan9303.c net: dsa: lan9303: handle hwaccel VLAN tags 2022-02-23 12:03:11 +01:00
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: dsa: felix: fix broken VLAN-tagged PTP under VLAN-aware bridge 2021-11-18 19:17:06 +01:00
tag_ocelot_8021q.c net: dsa: tag_ocelot_8021q: fix inability to inject STP BPDUs into BLOCKING ports 2021-10-12 17:35:19 -07:00
tag_qca.c net: dsa: create a helper for locating EtherType DSA headers on TX 2021-08-11 14:44:58 +01:00
tag_rtl4_a.c net: dsa: tag_rtl4_a: Fix egress tags 2021-09-01 11:48:05 +01:00
tag_sja1105.c net: dsa: tag_sja1105: always prefer source port information from INCL_SRCPT 2024-06-16 13:39:54 +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