CVE-2026-68284

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

bpf, sockmap: Fix cork use-after-free in tcpbpfsendmsg()

tcpbpfsendmsg() keeps msgtx across skstreamwaitmemory(), which drops and reacquires the socket lock. Its error path tries to decide whether msg_tx names the local temporary message by comparing it with the current value of psock->cork.

This comparison is unsafe when two threads send on the same socket:

Thread A Thread B msgtx = psock->cork skmsgalloc() fails skstreamwaitmemory() releases the socket lock acquires the socket lock completes the cork psock->cork = NULL frees the cork reacquires the socket lock msgtx != psock->cork skmsgfree(msgtx)

The stale cork is therefore mistaken for the local temporary message and freed again. KASAN reported:

BUG: KASAN: slab-use-after-free in skmsgfree+0x49/0x50 Read of size 4 at addr ffff88810c908800 by task poc/90 Call Trace: skmsgfree+0x49/0x50 tcpbpfsendmsg+0x14f5/0x1cc0 __sys_sendto+0x32c/0x3a0 __x64syssendto+0xdb/0x1b0 Allocated by task 89: __kasankmalloc+0x8f/0xa0 tcpbpf_sendmsg+0x16b3/0x1cc0 Freed by task 91: __kasanslabfree+0x43/0x70 kfree+0x131/0x3c0 tcpbpfsendmsg+0xec3/0x1cc0

msg_tx can only name the stack-local tmp or the shared cork. Check for tmp directly so a changed psock->cork cannot turn a shared message into an apparent local one.