CVE-2026-72222

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

sunrpc: pin svc_xprt across the asynchronous TLS handshake callback

svctcphandshake() stores the raw svcxprt pointer in tlshandshakeargs.tadata and submits the request through tlsserverhellox509(). The handshake core takes only sockhold(req->hrsk); nothing references the embedding struct svcsock that svctcphandshakedone() reaches via containerof().

Two close races leave the in-flight callback writing through a freed svcsock. svcsockfree() calls tlshandshakecancel() and discards its return value: a false return means handshakecomplete() has already set HANDSHAKEFREQCOMPLETED but hpdone() may not have finished, yet svcsockfree() proceeds to kfree(svsk). The cancel-loser fall-through inside svctcphandshake() itself produces the same window: when waitforcompletioninterruptibletimeout() returns <= 0 (timeout or signal) and tlshandshakecancel() returns false, the function does not drain, returns, and svchandlexprt() calls svcxprtreceived(), which clears XPTBUSY and can drop the last reference. A concurrent close then runs svcsockfree() while svctcphandshakedone() is still updating xptflags and walking svsk->skhandshake_done.

The corruption surfaces as setbit/clearbit RMW into the freed xptflags slab slot and as completeall() walking and writing the freed waitqueueheadt list embedded in skhandshakedone -- a slab-corruption primitive, not a benign read. The path is reachable on any TLS-enabled NFS server whenever a connection close overlaps the tlshd downcall delivery window; the interruptible wait means signal delivery suffices, not just SVCHANDSHAKE_TO expiry.

Take svcxprtget(xprt) immediately before tlsserverhellox509() so the in-flight callback owns its own reference. Release it on the two edges where the callback is guaranteed not to fire -- submission failure from tlsserverhellox509() and a successful tlshandshakecancel() -- and at the tail of svctcphandshakedone() after completeall().

[cel: rewrote commit message to describe the actual change]