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b=q7b66OmUWHmv9dj5zNmdqz+zz6pEB9NHpZjRSmb1+ljWVYWyqKG1i5gzWzFVYxyCZ r+mn8NKfd+JCCn802UOyIVTdVaKylr7REF0jax/e85DyPErtKY548uoKohzIQ0gyiY /uk4kyRGLVDvnT5L1SHIH613/O/Du6c2u0l1eedo= Date: Thu, 12 Mar 2026 13:55:14 -0700 From: Andrew Morton To: Josh Law Cc: Matthew Wilcox , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law Subject: Re: [PATCH v3 1/2] lib/idr: fix infinite loop in idr_get_next() Message-Id: <20260312135514.e4fc0fa4c1f50e6fbda2644c@linux-foundation.org> In-Reply-To: <20260312181948.20020-2-objecting@objecting.org> References: <20260312181948.20020-1-objecting@objecting.org> <20260312181948.20020-2-objecting@objecting.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 51703140004 X-Stat-Signature: paiwi8cksnu87qnqwis5zcgw3g1pats6 X-HE-Tag: 1773348916-680408 X-HE-Meta: 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 LeDiQDVC bYOOq8TRLAZ8Dw3L+vlZDYA8ocA3pKn/RSQgFvSl9WCBpc2GGkYe+AoKQeQlpMk1pSsrILQuQTE8Rz9UHoMJ/T5v0x7xHycmo1WWLrpv4OXN6BCjlY9uRoy2PxhQnidxw5Eru16m7xEr/txGUggp35gbHeHTLQCo/0oDNb8ZRBTL734yWK33ByJ/BgZ2j+iNGFDQIH+HsNjoIZluvaYr6+k02Vc6URzDhTieajuCSyv2f8gCQPJ7ASSNCPgYwMPuRkCTWL7dHQ977vRYxKg8MliOr5JPNAdEHTw8fwspg0yD8mjlMz8Xm9fP6fpHgz7kxEOtG Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 12 Mar 2026 18:19:47 +0000 Josh Law 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?