From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx140.postini.com [74.125.245.140]) by kanga.kvack.org (Postfix) with SMTP id 7488D6B0070 for ; Thu, 5 Jul 2012 15:21:54 -0400 (EDT) Received: by yenr5 with SMTP id r5so9647386yen.14 for ; Thu, 05 Jul 2012 12:21:53 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20120705104520.GA6773@latitude> References: <4FAC200D.2080306@codeaurora.org> <02fc01cd2f50$5d77e4c0$1867ae40$%szyprowski@samsung.com> <4FAD89DC.2090307@codeaurora.org> <015f01cd5a95$c1525dc0$43f71940$%szyprowski@samsung.com> <20120705104520.GA6773@latitude> Date: Thu, 5 Jul 2012 21:21:53 +0200 Message-ID: Subject: Re: Bad use of highmem with buffer_migrate_page? From: =?UTF-8?Q?Micha=C5=82_Nazarewicz?= Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Rabin Vincent Cc: Marek Szyprowski , Laura Abbott , linaro-mm-sig@lists.linaro.org, linux-arm-msm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, LKML 2012/7/5 Rabin Vincent : > From 8a94126eb3aa2824866405fb78bb0b8316f8fd00 Mon Sep 17 00:00:00 2001 > From: Rabin Vincent > Date: Thu, 5 Jul 2012 15:52:23 +0530 > Subject: [PATCH] mm: cma: don't replace lowmem pages with highmem > > The filesystem layer expects pages in the block device's mapping to not > be in highmem (the mapping's gfp mask is set in bdget()), but CMA can > currently replace lowmem pages with highmem pages, leading to crashes in > filesystem code such as the one below: > > Unable to handle kernel NULL pointer dereference at virtual address 00000400 > pgd = c0c98000 > [00000400] *pgd=00c91831, *pte=00000000, *ppte=00000000 > Internal error: Oops: 817 [#1] PREEMPT SMP ARM > CPU: 0 Not tainted (3.5.0-rc5+ #80) > PC is at __memzero+0x24/0x80 > ... > Process fsstress (pid: 323, stack limit = 0xc0cbc2f0) > Backtrace: > [] (ext4_getblk+0x0/0x180) from [] (ext4_bread+0x1c/0x98) > [] (ext4_bread+0x0/0x98) from [] (ext4_mkdir+0x160/0x3bc) > r4:c15337f0 > [] (ext4_mkdir+0x0/0x3bc) from [] (vfs_mkdir+0x8c/0x98) > [] (vfs_mkdir+0x0/0x98) from [] (sys_mkdirat+0x74/0xac) > r6:00000000 r5:c152eb40 r4:000001ff r3:c14b43f0 > [] (sys_mkdirat+0x0/0xac) from [] (sys_mkdir+0x20/0x24) > r6:beccdcf0 r5:00074000 r4:beccdbbc > [] (sys_mkdir+0x0/0x24) from [] (ret_fast_syscall+0x0/0x30) > > Fix this by replacing only highmem pages with highmem. > > Reported-by: Laura Abbott > Signed-off-by: Rabin Vincent Acked-by: Michal Nazarewicz > --- > mm/page_alloc.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 4403009..4a4f921 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -5635,7 +5635,12 @@ static struct page * > __alloc_contig_migrate_alloc(struct page *page, unsigned long private, > int **resultp) > { > - return alloc_page(GFP_HIGHUSER_MOVABLE); > + gfp_t gfp_mask = GFP_USER | __GFP_MOVABLE; > + > + if (PageHighMem(page)) > + gfp_mask |= __GFP_HIGHMEM; > + > + return alloc_page(gfp_mask); > } > > /* [start, end) must belong to a single zone. */ -- 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