CVE-2026-74684

Published: August 27, 2026Last modified: August 27, 2026

Description

In the Linux kernel, the following vulnerability has been resolved: net: tap: set skb->dev before parsing virtio net header in tap_get_user_xdp() The commit 4f61f133f354 ("net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null") fixed a crash in tap_get_user() by assigning skb->dev before calling tun_vnet_hdr_to_skb(). This is required because virtio_net_hdr_to_skb() may invoke dev_parse_header_protocol(), which dereferences skb->dev. Without the assignment, a NULL pointer dereference can occur. However, tap_get_user_xdp() still parses the virtio-net header before assigning skb->dev. When the vhost TX path passes an XDP buffer containing a GSO virtio-net header but the protocol is set to zero on purpose, tun_vnet_hdr_to_skb() can reach dev_parse_header_protocol() while skb->dev is still NULL, resulting in a crash. Fix this by looking up the tap device and assigning skb->dev before calling tun_vnet_hdr_to_skb(), matching the ordering already used in tap_get_user(). Preserve the existing RCU read-side critical section across dev_queue_xmit().

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References

• https://git.kernel.org/stable/c/15583b07fd691a844fbf7b3ad612cdc9e9a657c0
• https://git.kernel.org/stable/c/164c31ee252ebd1ac8f44c2dfc5486b6d9a0379b
• https://git.kernel.org/stable/c/3874892dd27d5387aa9a06f58d9060f18f351d24
• https://git.kernel.org/stable/c/8b444b126cd8e4473e652f529753ed4dd1360a9c