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Date: Thu, 12 Mar 2026 13:55:14 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Josh Law <hlcj1234567@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>, linux-fsdevel@vger.kernel.org,
 linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law
 <objecting@objecting.org>
Subject: Re: [PATCH v3 1/2] lib/idr: fix infinite loop in idr_get_next()
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On Thu, 12 Mar 2026 18:19:47 +0000 Josh Law <hlcj1234567@gmail.com> wrote:

> In idr_get_next(), if the returned id from idr_get_next_ul() is greater
> than INT_MAX, the function issues a warning and returns NULL without
> updating the *nextid pointer. This causes a soft lockup for any caller
> iterating over an IDR (e.g. via idr_for_each_entry) because they will
> receive NULL, fail to advance their index, and repeatedly query the same
> state forever.

This assumes that the idr_get_next() caller ignores the NULL return and
just keeps on looping.  Isn't that a caller bug and if so, do we need
to defend against it here?