In the Linux kernel, the following vulnerability has been resolved:

netfilter: handle unreadable frags

sashiko reports: When an skb with unreadable fragments (such as from devmem TCP, where skbfragsreadable(skb) returns false) is processed by the u32 module, skbcopybits() will safely return a negative error code [..]

xtu32: bail out with hotdrop in this case. gatherfrags: return -1, just as if we had no fragment header. nfnetlinkqueue: restrict to the linear part. nfnetlinklog: restrict to the linear part.

v2: - skbzerocopy helpers don't copy readable flag, i.e. nfnetlinkqueue is broken too xtu32 shouldn't return true if hotdrop was set.