From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ob0-f182.google.com (mail-ob0-f182.google.com [209.85.214.182]) by kanga.kvack.org (Postfix) with ESMTP id 8B6F16B0038 for ; Tue, 5 May 2015 21:40:07 -0400 (EDT) Received: by obblk2 with SMTP id lk2so115402324obb.0 for ; Tue, 05 May 2015 18:40:07 -0700 (PDT) Received: from mail-oi0-x234.google.com (mail-oi0-x234.google.com. [2607:f8b0:4003:c06::234]) by mx.google.com with ESMTPS id dh3si11174992oeb.1.2015.05.05.18.40.06 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 05 May 2015 18:40:06 -0700 (PDT) Received: by oift201 with SMTP id t201so163507635oif.3 for ; Tue, 05 May 2015 18:40:06 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150505142948.7fe0371558a581dbd9d52c51@linux-foundation.org> References: <1430732477-16977-1-git-send-email-zhuhui@xiaomi.com> <1430796179-1795-1-git-send-email-zhuhui@xiaomi.com> <20150505142948.7fe0371558a581dbd9d52c51@linux-foundation.org> From: Hui Zhu Date: Wed, 6 May 2015 09:39:26 +0800 Message-ID: Subject: Re: [PATCH v2] CMA: page_isolation: check buddy before access it Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Hui Zhu , vbabka@suse.cz, iamjoonsoo.kim@lge.com, lauraa@codeaurora.org, "linux-kernel@vger.kernel.org" , Linux Memory Management List On Wed, May 6, 2015 at 5:29 AM, Andrew Morton wrote: > On Tue, 5 May 2015 11:22:59 +0800 Hui Zhu wrote: > >> Change pfn_present to pfn_valid_within according to the review of Laura. >> >> I got a issue: >> [ 214.294917] Unable to handle kernel NULL pointer dereference at virtual address 0000082a >> [ 214.303013] pgd = cc970000 >> [ 214.305721] [0000082a] *pgd=00000000 >> [ 214.309316] Internal error: Oops: 5 [#1] PREEMPT SMP ARM >> [ 214.335704] PC is at get_pageblock_flags_group+0x5c/0xb0 >> [ 214.341030] LR is at unset_migratetype_isolate+0x148/0x1b0 >> [ 214.346523] pc : [] lr : [] psr: 80000093 >> [ 214.346523] sp : c7029d00 ip : 00000105 fp : c7029d1c >> [ 214.358005] r10: 00000001 r9 : 0000000a r8 : 00000004 >> [ 214.363231] r7 : 60000013 r6 : 000000a4 r5 : c0a357e4 r4 : 00000000 >> [ 214.369761] r3 : 00000826 r2 : 00000002 r1 : 00000000 r0 : 0000003f >> [ 214.376291] Flags: Nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment user >> [ 214.383516] Control: 10c5387d Table: 2cb7006a DAC: 00000015 >> [ 214.949720] Backtrace: >> [ 214.952192] [] (get_pageblock_flags_group+0x0/0xb0) from [] (unset_migratetype_isolate+0x148/0x1b0) >> [ 214.962978] r7:60000013 r6:c0a357c0 r5:c0a357e4 r4:c1555000 >> [ 214.968693] [] (unset_migratetype_isolate+0x0/0x1b0) from [] (undo_isolate_page_range+0xd0/0xdc) >> [ 214.979222] [] (undo_isolate_page_range+0x0/0xdc) from [] (__alloc_contig_range+0x254/0x34c) >> [ 214.989398] r9:000abc00 r8:c7028000 r7:000b1f53 r6:000b3e00 r5:00000005 >> r4:c7029db4 >> [ 214.997308] [] (__alloc_contig_range+0x0/0x34c) from [] (alloc_contig_range+0x14/0x18) >> [ 215.006973] [] (alloc_contig_range+0x0/0x18) from [] (dma_alloc_from_contiguous_addr+0x1ac/0x304) >> >> This issue is because when call unset_migratetype_isolate to unset a part >> of CMA memory, it try to access the buddy page to get its status: >> if (order >= pageblock_order) { >> page_idx = page_to_pfn(page) & ((1 << MAX_ORDER) - 1); >> buddy_idx = __find_buddy_index(page_idx, order); >> buddy = page + (buddy_idx - page_idx); >> >> if (!is_migrate_isolate_page(buddy)) { >> But the begin addr of this part of CMA memory is very close to a part of >> memory that is reserved in the boot time (not in buddy system). >> So add a check before access it. >> >> ... >> >> --- a/mm/page_isolation.c >> +++ b/mm/page_isolation.c >> @@ -101,7 +101,8 @@ void unset_migratetype_isolate(struct page *page, unsigned migratetype) >> buddy_idx = __find_buddy_index(page_idx, order); >> buddy = page + (buddy_idx - page_idx); >> >> - if (!is_migrate_isolate_page(buddy)) { >> + if (!pfn_valid_within(page_to_pfn(buddy)) >> + || !is_migrate_isolate_page(buddy)) { >> __isolate_free_page(page, order); >> kernel_map_pages(page, (1 << order), 1); >> set_page_refcounted(page); > > This fix is needed in kernel versions 4.0.x isn't it? I think it need it. Thanks, Hui -- 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