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| author | Jakob Unterwurzacher <jakobunt@gmail.com> | 2025-09-05 14:14:36 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-09-09 18:54:20 +0200 |
| commit | cf3c78ecdfa6b8d9d44fc78b860fba72608d2004 (patch) | |
| tree | 73ab558fc04df51d951794538d8484ef329eca22 /net | |
| parent | 062c74a26266831402ed6419eb93358a24f67ee5 (diff) | |
| download | linux-cf3c78ecdfa6b8d9d44fc78b860fba72608d2004.tar.gz linux-cf3c78ecdfa6b8d9d44fc78b860fba72608d2004.tar.bz2 linux-cf3c78ecdfa6b8d9d44fc78b860fba72608d2004.zip | |
net: dsa: microchip: linearize skb for tail-tagging switches
[ Upstream commit ba54bce747fa9e07896c1abd9b48545f7b4b31d2 ]
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: 016e43a26bab ("net: dsa: ksz: Add KSZ8795 tag code")
Fixes: 8b8010fb7876 ("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>
Diffstat (limited to 'net')
| -rw-r--r-- | net/dsa/tag_ksz.c | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c index 809de53d443c..d58bcd16d597 100644 --- a/net/dsa/tag_ksz.c +++ b/net/dsa/tag_ksz.c @@ -69,7 +69,12 @@ static struct sk_buff *ksz8795_xmit(struct sk_buff *skb, struct net_device *dev) static struct sk_buff *ksz8795_rcv(struct sk_buff *skb, struct net_device *dev) { - u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN; + u8 *tag; + + if (skb_linearize(skb)) + return NULL; + + tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN; return ksz_common_rcv(skb, dev, tag[0] & 7, KSZ_EGRESS_TAG_LEN); } @@ -136,10 +141,16 @@ static struct sk_buff *ksz9477_xmit(struct sk_buff *skb, static struct sk_buff *ksz9477_rcv(struct sk_buff *skb, struct net_device *dev) { - /* Tag decoding */ - u8 *tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN; - unsigned int port = tag[0] & KSZ9477_TAIL_TAG_EG_PORT_M; unsigned int len = KSZ_EGRESS_TAG_LEN; + unsigned int port; + u8 *tag; + + if (skb_linearize(skb)) + return NULL; + + /* Tag decoding */ + tag = skb_tail_pointer(skb) - KSZ_EGRESS_TAG_LEN; + port = tag[0] & KSZ9477_TAIL_TAG_EG_PORT_M; /* Extra 4-bytes PTP timestamp */ if (tag[0] & KSZ9477_PTP_TAG_INDICATION) |