ipsec-2026-07-29

xfrm: fix xfrm_state_construct() auth-trunc leak

attach_auth_trunc() can allocate x->aalg while leaving
x->props.aalgo at zero when the selected auth algorithm has no
sadb_alg_id. One real case is cmac(aes).

xfrm_state_construct() then treats !x->props.aalgo as "no auth
algorithm attached yet" and calls attach_auth(). That overwrites
x->aalg and loses the first allocation. Any later failure or teardown
only frees the replacement pointer.

Check whether x->aalg is already attached instead of inferring that
state from x->props.aalgo.

Fixes: 4447bb33f094 ("xfrm: Store aalg in xfrm_state with a user specified truncation length")
Cc: stable@vger.kernel.org
Reported-by: Vega <vega@nebusec.ai>
Assisted-by: Codex:gpt-5.4
Signed-off-by: Zihan Xi <zihanx@nebusec.ai>
Signed-off-by: Ren Wei <enjou1224z@gmail.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>