From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752466AbaDVGVh (ORCPT ); Tue, 22 Apr 2014 02:21:37 -0400 Received: from cn.fujitsu.com ([59.151.112.132]:18477 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1751354AbaDVGUQ (ORCPT ); Tue, 22 Apr 2014 02:20:16 -0400 X-IronPort-AV: E=Sophos;i="4.97,899,1389715200"; d="scan'208";a="29554475" From: Lai Jiangshan To: CC: Andrew Morton , Tejun Heo , Lai Jiangshan , , Jean Delvare , Monam Agarwal , Jeff Layton , Andreas Gruenbacher , Stephen Hemminger Subject: [PATCH 1/7 V3] idr: fix overflow bug during maximum ID calculation at maximum height Date: Tue, 22 Apr 2014 14:23:23 +0800 Message-ID: <1398147810-26414-2-git-send-email-laijs@cn.fujitsu.com> X-Mailer: git-send-email 1.7.4.4 In-Reply-To: <1398147810-26414-1-git-send-email-laijs@cn.fujitsu.com> References: <20140421152345.4d67a6563ebd89f0b969332f@linux-foundation.org> <1398147810-26414-1-git-send-email-laijs@cn.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.167.226.103] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org idr_replace() open-codes the logic to calculate the maximum valid ID given the height of the idr tree; unfortunately, the open-coded logic doesn't account for the fact that the top layer may have unused slots and over-shifts the limit to zero when the tree is at its maximum height. The following test code shows it fails to replace the value for id=((1<<27)+42): static void test5(void) { int id; DEFINE_IDR(test_idr); #define TEST5_START ((1<<27)+42) /* use the highest layer */ printk(KERN_INFO "Start test5\n"); id = idr_alloc(&test_idr, (void *)1, TEST5_START, 0, GFP_KERNEL); BUG_ON(id != TEST5_START); TEST_BUG_ON(idr_replace(&test_idr, (void *)2, TEST5_START) != (void *)1); idr_destroy(&test_idr); printk(KERN_INFO "End of test5\n"); } Fix the bug by using idr_max() which correctly takes into account the maximum allowed shift. sub_alloc() shares the same problem and may incorrectly fail with -EAGAIN; however, this bug doesn't affect correct operation because idr_get_empty_slot(), which already uses idr_max(), retries with the increased @id in such cases. tj: Updated patch description. CC: stable@vger.kernel.org Signed-off-by: Lai Jiangshan Acked-by: Tejun Heo --- lib/idr.c | 8 +++----- 1 files changed, 3 insertions(+), 5 deletions(-) diff --git a/lib/idr.c b/lib/idr.c index 2642fa8..4df6792 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -249,7 +249,7 @@ static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa, id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1; /* if already at the top layer, we need to grow */ - if (id >= 1 << (idp->layers * IDR_BITS)) { + if (id > idr_max(idp->layers)) { *starting_id = id; return -EAGAIN; } @@ -811,12 +811,10 @@ void *idr_replace(struct idr *idp, void *ptr, int id) if (!p) return ERR_PTR(-EINVAL); - n = (p->layer+1) * IDR_BITS; - - if (id >= (1 << n)) + if (id > idr_max(p->layer + 1)) return ERR_PTR(-EINVAL); - n -= IDR_BITS; + n = p->layer * IDR_BITS; while ((n > 0) && p) { p = p->ary[(id >> n) & IDR_MASK]; n -= IDR_BITS; -- 1.7.4.4