[PATCH 6.19 083/342] xfrm: iptfs: fix skb_put() panic on non-linear skb during reassembly

Greg Kroah-Hartman
2026-03-31T16:34:52Z

From: Fernando Fernandez Mancera <fmancera@suse.de>

[ Upstream commit 0b352f83cabfefdaafa806d6471f0eca117dc7d5 ]

In iptfs_reassem_cont(), IP-TFS attempts to append data to the new inner
packet 'newskb' that is being reassembled. First a zero-copy approach is
tried if it succeeds then newskb becomes non-linear.

When a subsequent fragment in the same datagram does not meet the
fast-path conditions, a memory copy is performed. It calls skb_put() to
append the data and as newskb is non-linear it triggers
SKB_LINEAR_ASSERT check.

Oops: invalid opcode: 0000 [#1] SMP NOPTI
[...]
RIP: 0010:skb_put+0x3c/0x40
[...]
Call Trace:
<IRQ>
iptfs_reassem_cont+0x1ab/0x5e0 [xfrm_iptfs]
iptfs_input_ordered+0x2af/0x380 [xfrm_iptfs]
iptfs_input+0x122/0x3e0 [xfrm_iptfs]
xfrm_input+0x91e/0x1a50
xfrm4_esp_rcv+0x3a/0x110
ip_protocol_deliver_rcu+0x1d7/0x1f0
ip_local_deliver_finish+0xbe/0x1e0
__netif_receive_skb_core.constprop.0+0xb56/0x1120
__netif_receive_skb_list_core+0x133/0x2b0
netif_receive_skb_list_internal+0x1ff/0x3f0
napi_complete_done+0x81/0x220
virtnet_poll+0x9d6/0x116e [virtio_net]
__napi_poll.constprop.0+0x2b/0x270
net_rx_action+0x162/0x360
handle_softirqs+0xdc/0x510
__irq_exit_rcu+0xe7/0x110
irq_exit_rcu+0xe/0x20
common_interrupt+0x85/0xa0
</IRQ>
<TASK>

Fix this by checking if the skb is non-linear. If it is, linearize it by
calling skb_linearize(). As the initial allocation of newskb originally
reserved enough tailroom for the entire reassembled packet we do not
need to check if we have enough tailroom or extend it.

Fixes: 5f2b6a909574 ("xfrm: iptfs: add skb-fragment sharing code")
Reported-by: Hao Long <me@imlonghao.com>
Closes: https://lore.kernel.org/netdev/DGRCO9SL0T5U.JTINSHJQ9KPK@imlonghao.com/
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/xfrm/xfrm_iptfs.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/net/xfrm/xfrm_iptfs.c b/net/xfrm/xfrm_iptfs.c
index 3b6d7284fc70a..4e270628fc347 100644
--- a/net/xfrm/xfrm_iptfs.c
+++ b/net/xfrm/xfrm_iptfs.c
@@ -901,6 +901,12 @@ static u32 iptfs_reassem_cont(struct xfrm_iptfs_data *xtfs, u64 seq,
iptfs_skb_can_add_frags(newskb, fragwalk, data, copylen)) {
iptfs_skb_add_frags(newskb, fragwalk, data, copylen);
} else {
+ if (skb_linearize(newskb)) {
+ XFRM_INC_STATS(xs_net(xtfs->x),
+ LINUX_MIB_XFRMINBUFFERERROR);
+ goto abandon;
+ }
+
/* copy fragment data into newskb */
if (skb_copy_seq_read(st, data, skb_put(newskb, copylen),
copylen)) {
--
2.51.0