From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx141.postini.com [74.125.245.141]) by kanga.kvack.org (Postfix) with SMTP id 6A89B6B0002 for ; Thu, 21 Feb 2013 14:33:58 -0500 (EST) Message-ID: <51267695.8090800@synopsys.com> Date: Fri, 22 Feb 2013 01:03:41 +0530 From: Vineet Gupta MIME-Version: 1.0 Subject: Re: [PATCH 1/2] memblock: add assertion for zero allocation size References: <1361471962-25164-1-git-send-email-vgupta@synopsys.com> <1361471962-25164-2-git-send-email-vgupta@synopsys.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yinghai Lu Cc: "H. Peter Anvin" , Andrew Morton , Chris Zankel , Max Filippov , Marc Gauthier , Tejun Heo , Wanpeng Li , Ingo Molnar , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Friday 22 February 2013 12:57 AM, Yinghai Lu wrote: > [+Cc: hpa] > > On Thu, Feb 21, 2013 at 10:39 AM, Vineet Gupta > wrote: >> This came to light when calling memblock allocator from arc port (for >> copying flattended DT). If a "0" alignment is passed, the allocator >> round_up() call incorrectly rounds up the size to 0. >> >> round_up(num, alignto) => ((num - 1) | (alignto -1)) + 1 >> >> While the obvious allocation failure causes kernel to panic, it is >> better to BUG_ON() if effective size for allocation (as passed by caller >> and/or computed after alignemtn rounding) is zero. > should we just make align to 1 instead of 0 ? Where - you mean if user passes 0, just make it 1. Nah - it's better to complain and get the call site fixed ! > or BUG_ON(!align) instead? That could be done too but you would also need BUG_ON(!size) - to catch another API abuse. BUG_ON(!size) however catches both the cases. > >> Signed-off-by: Vineet Gupta >> Cc: Andrew Morton >> Cc: Tejun Heo >> Cc: Yinghai Lu >> Cc: Wanpeng Li >> Cc: Ingo Molnar >> Cc: linux-mm@kvack.org >> Cc: linux-kernel@vger.kernel.org >> --- >> mm/memblock.c | 2 ++ >> 1 files changed, 2 insertions(+), 0 deletions(-) >> >> diff --git a/mm/memblock.c b/mm/memblock.c >> index 1bcd9b9..32b36d0 100644 >> --- a/mm/memblock.c >> +++ b/mm/memblock.c >> @@ -824,6 +824,8 @@ static phys_addr_t __init memblock_alloc_base_nid(phys_addr_t size, >> /* align @size to avoid excessive fragmentation on reserved array */ >> size = round_up(size, align); >> >> + BUG_ON(!size); >> + >> found = memblock_find_in_range_node(0, max_addr, size, align, nid); >> if (found && !memblock_reserve(found, size)) >> return found; >> -- >> 1.7.4.1 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org