In the Linux kernel, the following vulnerability has been resolved:
phonet: pep: fix use-after-free in pep_get_sb()
pep_get_sb() doesnt consider that pskb_may_pull() might have relocated the skb data, and continue to access the older pointer, causing UAF.
Reproduced under KASAN:
BUG: KASAN: slab-use-after-free in pep_get_sb+0x234/0x3b0 Read of size 1 at addr ff11000105510f50 by task repro/157 pep_get_sb+0x234/0x3b0 pipe_handler_do_rcv+0x5f7/0xa10 pep_do_rcv+0x203/0x410 __sk_receive_skb+0x471/0x4a0 phonet_rcv+0x5b3/0x6c0 __netif_receive_skb+0xcc/0x1d0
Refetch the header with skb_header_pointer() after pskb_may_pull(), so the possibly stale pointer is no longer dereferenced. There are better ways to solve this, but, this is the less instrusive one.
References
- https://git.kernel.org/stable/c/0f71f852a96af9685858ce59fda34ecbf85c283d
- https://git.kernel.org/stable/c/17f78c0c0d41d738ee236eb6e841e39395188054
- https://git.kernel.org/stable/c/25e3641beb51333bfbb155af2fd2573a61113af2
- https://git.kernel.org/stable/c/8d931a75a38b9bb584a4071f5ebbd52755fc35ee
- https://git.kernel.org/stable/c/a48a889b60f73edb0399a8b08284a2ab0bd0295f