xfrm: bound nat keepalive state collection

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The v1 nat keepalive fix allocates a GFP_ATOMIC object for every state
while collecting references for phase two. This makes the worker's
temporary memory use depend on the number of states and lets -ENOMEM abort
the scan.

Replace the allocated list with a fixed-size batch. When the batch is full,
return a private walk status so xfrm_state_walk() leaves a cursor; drain
the references after the walk releases xfrm_state_lock and resume from
the cursor. This bounds temporary memory use and avoids the allocation
failure path.

The v1 fix also moved nat_keepalive_send() out of the walk callback. Keep
the phase-two drain BH-disabled, as required by local_lock_nested_bh()
used by the keepalive sockets.

Fixes: 763fe700b7 ("xfrm: avoid lock inversion in nat keepalive work")
Cc: stable@vger.kernel.org
Cc: Eyal Birger <eyal.birger@gmail.com>
Reported-by: Vega <vega@nebusec.ai>
Assisted-by: Codex:gpt-5.4
Signed-off-by: Zihan Xi <zihanx@nebusec.ai>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

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Zihan Xi 2026-08-17 19:09:56 +00:00 • committed by Steffen Klassert

parent 0fda52de8b

commit 4e9442ce55

1 changed files with 21 additions and 25 deletions

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net/xfrm/xfrm_nat_keepalive.c

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