Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in radix_tree_next_chunk()

From: "Toralf Förster" <toralf.foerster@gmx.de>
To: Konstantin Khlebnikov <koct9i@gmail.com>
Cc: Richard Weinberger <richard@nod.at>,
	Richard Weinberger <richard.weinberger@gmail.com>,
	Linux Kernel <linux-kernel@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	UML devel <user-mode-linux-devel@lists.sourceforge.net>
Subject: Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in radix_tree_next_chunk()
Date: Wed, 06 Nov 2013 22:18:53 +0100	[thread overview]
Message-ID: <527AB23D.2060305@gmx.de> (raw)
In-Reply-To: <CALYGNiPvJF1u8gXNcX1AZR5-VkGqJnaose84KBbdaoBAq8aoGQ@mail.gmail.com>

On 11/06/2013 05:06 PM, Konstantin Khlebnikov wrote:
> In this case it must stop after scanning whole tree in line:
> /* Overflow after ~0UL */
> if (!index)
>   return NULL;
> 

A fresh current example with latest git tree shows that lines 769 and 770 do alternate :

tfoerste@n22 ~/devel/linux $ sudo gdb /usr/local/bin/linux-v3.12-48-gbe408cd 16619 -n -batch -ex bt
0x08296a8c in radix_tree_next_chunk (root=0x25, iter=0x462e7c64, flags=12) at lib/radix-tree.c:770
770                                             if (node->slots[offset])
#0  0x08296a8c in radix_tree_next_chunk (root=0x25, iter=0x462e7c64, flags=12) at lib/radix-tree.c:770
#1  0x080cc1fe in find_get_pages (mapping=0x462ad470, start=0, nr_pages=14, pages=0xc) at mm/filemap.c:844
#2  0x080d5d6a in pagevec_lookup (pvec=0x462e7cc8, mapping=0x25, start=37, nr_pages=37) at mm/swap.c:914
#3  0x080d615a in truncate_inode_pages_range (mapping=0x462ad470, lstart=0, lend=-1) at mm/truncate.c:241
#4  0x080d64ff in truncate_inode_pages (mapping=0x25, lstart=51539607589) at mm/truncate.c:358

tfoerste@n22 ~/devel/linux $ sudo gdb /usr/local/bin/linux-v3.12-48-gbe408cd 16619 -n -batch -ex bt
radix_tree_next_chunk (root=0x28, iter=0x462e7c64, flags=18) at lib/radix-tree.c:769
769                                     while (++offset < RADIX_TREE_MAP_SIZE) {
#0  radix_tree_next_chunk (root=0x28, iter=0x462e7c64, flags=18) at lib/radix-tree.c:769
#1  0x080cc1fe in find_get_pages (mapping=0x462ad470, start=0, nr_pages=14, pages=0x12) at mm/filemap.c:844
#2  0x080d5d6a in pagevec_lookup (pvec=0x462e7cc8, mapping=0x28, start=40, nr_pages=40) at mm/swap.c:914
#3  0x080d615a in truncate_inode_pages_range (mapping=0x462ad470, lstart=0, lend=-1) at mm/truncate.c:241
#4  0x080d64ff in truncate_inode_pages (mapping=0x28, lstart=77309411368) at mm/truncate.c:358
#5  0x0825e388 in hostfs_evict_inode (inode=0x462ad3b8) at fs/hostfs/hostfs_kern.c:242
#6  0x0811a8df in evict (inode=0x462ad3b8) at fs/inode.c:549

-- 
MfG/Sincerely
Toralf FA?rster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3

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