From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753614AbbINM6B (ORCPT ); Mon, 14 Sep 2015 08:58:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46893 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751816AbbINM6A (ORCPT ); Mon, 14 Sep 2015 08:58:00 -0400 From: Vitaly Kuznetsov To: Andrew Morton Cc: Andy Shevchenko , Rasmus Villemoes , James Bottomley , linux-kernel@vger.kernel.org, "K. Y. Srinivasan" Subject: [PATCH v2] lib/string_helpers.c: fix infinite loop in string_get_size() Date: Mon, 14 Sep 2015 14:57:56 +0200 Message-Id: <1442235476-31837-1-git-send-email-vkuznets@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Some string_get_size() calls (e.g.: string_get_size(1, 512, STRING_UNITS_10, ..., ...) string_get_size(15, 64, STRING_UNITS_10, ..., ...) ) result in an infinite loop. The problem is that if size is equal to divisor[units]/blk_size and is smaller than divisor[units] we'll end up with size == 0 when we start doing sf_cap calculations: For string_get_size(1, 512, STRING_UNITS_10, ..., ...) case: ... remainder = do_div(size, divisor[units]); -> size is 0, remainder is 1 remainder *= blk_size; -> remainder is 512 ... size *= blk_size; -> size is still 0 size += remainder / divisor[units]; -> size is still 0 The caller causing the issue is sd_read_capacity(), the problem was noticed on Hyper-V, such weird size was reported by host when scanning collides with device removal. This is probably a separate issue worth fixing, this patch is intended to prevent the library routing from infinite looping. Signed-off-by: Vitaly Kuznetsov --- lib/string_helpers.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/string_helpers.c b/lib/string_helpers.c index c98ae81..d0e607c 100644 --- a/lib/string_helpers.c +++ b/lib/string_helpers.c @@ -59,7 +59,7 @@ void string_get_size(u64 size, u64 blk_size, const enum string_size_units units, } exp = divisor[units] / (u32)blk_size; - if (size >= exp) { + if (size > exp) { remainder = do_div(size, divisor[units]); remainder *= blk_size; i++; -- 2.4.3