wireguard: netlink: access device through ctx instead of peer

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: wireguard: netlink: access device through ctx instead of peer The previous commit fixed a bug that led to a NULL peer->device being dereferenced. It's actually easier and faster performance-wise to instead get the device from ctx->wg. This semantically makes more sense too, since ctx->wg->peer_allowedips.seq is compared with ctx->allowedips_seq, basing them both in ctx. This also acts as a defence in depth provision against freed peers.

References

• https://git.kernel.org/stable/c/493aa6bdcffd90a4f82aa614fe4f4db0641b4068
• https://git.kernel.org/stable/c/4be453271a882c8ebc28df3dbf9e4d95e6ac42f5
• https://git.kernel.org/stable/c/09c3fa70f65175861ca948cb2f0f791e666c90e5
• https://git.kernel.org/stable/c/c991567e6c638079304cc15dff28748e4a3c4a37
• https://git.kernel.org/stable/c/93bcc1752c69bb309f4d8cfaf960ef1faeb34996
• https://git.kernel.org/stable/c/d44bd323d8bb8031eef4bdc44547925998a11e47
• https://git.kernel.org/stable/c/71cbd32e3db82ea4a74e3ef9aeeaa6971969c86f