rpcrdma: arm rn_done before publishing the notification

rpcrdma_rn_register() inserts @rn into rd_xa with xa_alloc() before
storing the caller's callback in rn->rn_done. The xarray makes @rn
reachable to rpcrdma_remove_one(), which walks rd_xa and invokes
rn->rn_done(rn) for every registered notification. A device removal
that races a fresh registration can therefore observe @rn with
rn_done still NULL, because the notification objects are zero
allocated by their owners, and call through a NULL function pointer.

Store rn->rn_done before xa_alloc() publishes @rn. The xarray's
store-side and load-side ordering then guarantees that any CPU which
finds @rn in rd_xa also observes the armed callback.

rpcrdma_rn_unregister() treats a non-NULL rn_done as the sentinel
for a completed registration, so the early store must not survive a
failed registration. Clear rn_done again when xa_alloc() fails.
Were it left set, the failed-accept cleanup path would call
rpcrdma_rn_unregister() on an @rn that was never inserted, erasing
an unrelated rd_xa slot and underflowing rd_kref.

Fixes: 7e86845a0346 ("rpcrdma: Implement generic device removal")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260601201703.46078-1-cel@kernel.org
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

0 files changed, 0 insertions, 0 deletions