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[37.27.107.159]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5a15602e7d9sm1085336e87.35.2026.03.12.11.19.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2026 11:19:49 -0700 (PDT) From: Josh Law X-Google-Original-From: Josh Law To: Matthew Wilcox , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law Subject: [PATCH v3 1/2] lib/idr: fix infinite loop in idr_get_next() Date: Thu, 12 Mar 2026 18:19:47 +0000 Message-Id: <20260312181948.20020-2-objecting@objecting.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260312181948.20020-1-objecting@objecting.org> References: <20260312181948.20020-1-objecting@objecting.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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. Fix this by setting *nextid to INT_MAX when the bounds check fails, ensuring the caller's iteration will terminate. Also update the idr_get_next() test case in the radix-tree test suite to expect INT_MAX instead of 0 when hitting this condition. Signed-off-by: Josh Law --- lib/idr.c | 4 +++- tools/testing/radix-tree/idr-test.c | 2 +- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/lib/idr.c b/lib/idr.c index f25bd2b9e9a4..07098eb4ddc3 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -268,8 +268,10 @@ void *idr_get_next(struct idr *idr, int *nextid) unsigned long id = *nextid; void *entry = idr_get_next_ul(idr, &id); - if (WARN_ON_ONCE(id > INT_MAX)) + if (WARN_ON_ONCE(id > INT_MAX)) { + *nextid = INT_MAX; return NULL; + } *nextid = id; return entry; } diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c index 945144e98507..bf6a0da6a50a 100644 --- a/tools/testing/radix-tree/idr-test.c +++ b/tools/testing/radix-tree/idr-test.c @@ -213,7 +213,7 @@ void idr_u32_test1(struct idr *idr, u32 handle) ptr = idr_get_next(idr, &sid); if (id > INT_MAX) { BUG_ON(ptr != NULL); - BUG_ON(sid != 0); + BUG_ON(sid != INT_MAX); } else { BUG_ON(ptr != DUMMY_PTR); BUG_ON(sid != id); -- 2.34.1