AZL-90107

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

net/sched: fix pedit partial COW leading to page cache corruption

tcfpeditact() computes the COW range for skbensurewritable() once before the key loop using tcfpoffmax_hint, but the hint does not account for the runtime header offset added by typed keys. This can leave part of the write region un-COW'd.

Fix by moving skbensurewritable() inside the per-key loop where the actual write offset is known, and add overflow checking on the offset arithmetic. For negative offsets (e.g. Ethernet header edits at ingress), use skbcow() to COW the headroom instead. Guard offsetvalid() against INT_MIN, where negation is undefined.