CVE-2026-80851

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

gtp: serialize PDP context updates

PDP contexts can be deleted through GTP_CMD_DELPDP or while the GTP
network device is being unregistered. The latter is serialized by RTNL,
but the generic-netlink delete path only holds RCU.

Running both paths concurrently can therefore make both paths delete the
same PDP context. The issue was found through static analysis and
reproduced on a KASAN-enabled kernel by a simple two-thread program
racing GTP_CMD_DELPDP against RTM_DELLINK:

  Oops: general protection fault, probably for non-canonical address
  KASAN: maybe wild-memory-access in range
         [0xdead000000000120-0xdead000000000127]
  RIP: gtp_genl_del_pdp+0x1c1/0x420 [gtp]
  RBP: dead000000000122

The second deletion dereferenced the poisoned hlist pprev pointer.

Serialize gtp_pdp_add(), gtp_genl_del_pdp(), and gtp_dellink() with a
shared mutex. Keep the mutex held until the final use of a PDP context in
the NEWPDP path, and keep the RCU read-side section around the complete
PDP context use in the DELPDP path.