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NFSv4 bitmap word counts come from the server. Once an XDR cursor failed, two loops kept decrementing the declared count, allowing a short reply to consume billions of iterations. Stop both walks on cursor failure, matching the existing reclaim path.
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NFSv4 bitmap word counts in fattr4 and OPEN replies come from the
server. nfs4_get_fattr() and nfs4_open_create() keep decrementing the
declared count after the XDR cursor has failed, so a short malicious
reply with a maximum count forces billions of iterations and stalls the
frontend.
Stop the bitmap walks when the cursor fails, matching the existing safe
nfs4_open_reclaim() path. This preserves support for extra bitmap words
while bounding the work to bytes actually received.