[PATCH net v3] octeontx2-pf: fix skb use-after-free with ipsec crypto offload

otx2_dma_map_skb_frag() calls skb_unclone_full() on its own copy of the
skb pointer. For a cloned skb, for example with tcpdump running on the
interface, this frees the skb and the new copy is lost on return. The
transmit path then uses the freed skb and the copy leaks.

Make the skb writable in place in otx2_sq_append_skb() instead, so the
pointer stays valid. Also do this for nonlinear skbs, as the hardware
writes the encrypted data back into the frags, which may be shared,
for example with the TCP retransmit queue.

Fixes: 195c3d463181 ("octeontx2-pf: map skb data as device writeable")
Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
This was flagged in the clashiko review of my skb_unshare() rename patch [1].

Compile-tested only, I have no octeontx2 hardware.

[1] https://lore.kernel.org/all/20261015-nb-skb-unclone-full-v1-1-0dfbf01f60f2@tipi-net.de/ (local)
---
Changes in v3:
- Also copy nonlinear skbs, GSO segments share frag pages with TCP
  (sashiko, Paolo)
- Count the drop in tx_discards
- The other pre-existing issues flagged on v2 will follow separately
- Link to v2: https://patch.msgid.link/20261022-nb-otx2-xfrm-unshare-net-v2-1-5590c9325bcd@tipi-net.de (local)

Changes in v2:
- Also handle skbs with shared frags (Jakub)
- Note: conflicts with "net: rename skb_unshare() to skb_unclone_full()"
  in net-next, the resolution is to drop the skb_unclone_full() line
- Link to v1: https://patch.msgid.link/20261019-nb-otx2-xfrm-unshare-net-v1-1-ee9b24f9e673@tipi-net.de (local)

To: Sunil Goutham <sgoutham@marvell.com>
To: Geetha sowjanya <gakula@marvell.com>
To: Ratheesh Kannoth <rkannoth@marvell.com>
To: Subbaraya Sundeep <sbhatta@marvell.com>
To: Bharat Bhushan <bbhushan2@marvell.com>
To: Andrew Lunn <andrew+netdev@lunn.ch>
To: "David S. Miller" <davem@davemloft.net>
To: Eric Dumazet <edumazet@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
Cc: <redacted>
Cc: <redacted>
---
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c | 4 +---
 drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c   | 9 +++++++++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
index 4e418c7456b7e..c441c0161dbf4 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_common.c

@@ -2115,10 +2115,8 @@ dma_addr_t otx2_dma_map_skb_frag(struct otx2_nic *pfvf,
 	int offset;
 
 	/* Crypto hardware need write permission for ipsec crypto offload */
-	if (unlikely(xfrm_offload(skb))) {
+	if (unlikely(xfrm_offload(skb)))
 		dir = DMA_BIDIRECTIONAL;
-		skb = skb_unclone_full(skb, GFP_ATOMIC);
-	}
 
 	/* First segment is always skb->data */
 	if (!seg) {

diff --git a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
index 8d2d607bc92f9..3d38ca2402e38 100644
--- a/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c
+++ b/drivers/net/ethernet/marvell/octeontx2/nic/otx2_txrx.c

@@ -1205,6 +1205,15 @@ bool otx2_sq_append_skb(void *dev, struct netdev_queue *txq,
 	if (free_desc < otx2_get_sqe_count(pfvf, skb))
 		return false;
 
+	/* Crypto hardware need write permission for ipsec crypto offload */
+	if (unlikely(xfrm_offload(skb)) &&
+	    (skb_cloned(skb) || skb_is_nonlinear(skb)) &&
+	    skb_ensure_writable(skb, skb->len)) {
+		atomic_long_inc(&pfvf->hw.dev_stats.tx_discards);
+		dev_kfree_skb_any(skb);
+		return true;
+	}
+
 	num_segs = skb_shinfo(skb)->nr_frags + 1;
 
 	/* If SKB doesn't fit in a single SQE, linearize it.

---
base-commit: 2cffcf1aeabb187e4f08fe4f5363128a3c45d786
change-id: 20261019-nb-otx2-xfrm-unshare-net-6b74a96a8d9e

Best regards,
--  
Nicolai Buchwitz [off-list ref]