sunrpc: defer rq_argp and rq_resp free until after RCU grace period

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svc_rqst_free() frees rqstp->rq_argp and rqstp->rq_resp synchronously
via kfree(), but defers the rqstp struct free via kfree_rcu().  After
svc_exit_thread() calls list_del_rcu() and svc_rqst_free(), there is
a window where RCU readers that started before list_del_rcu() can still
traverse the thread list and find the rqstp.  These readers (e.g.
nfsd_nl_rpc_status_get_dumpit()) dereference rqstp->rq_argp, which has
already been freed — a use-after-free.

Fix this by moving the kfree of rq_argp and rq_resp into an explicit
call_rcu() callback alongside the struct free.  Resources not accessed
by RCU readers (bvec, buffer pages, scratch folio, auth_data) remain
synchronously freed.

Fixes: 812443865c ("sunrpc: add a rcu_head to svc_rqst and use kfree_rcu to free it")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://patch.msgid.link/20260611-nfsd-testing-v2-4-5b90e276f2d9@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

...

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Jeff Layton 2026-06-11 16:00:47 -04:00 • committed by Chuck Lever

parent e13d505af7

commit c479bde671

1 changed files with 10 additions and 3 deletions

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net/sunrpc/svc.c

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