linux-kernel - Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in radix_tree_next

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Date:	Sat, 09 Nov 2013 20:07:22 +0100
From:	Toralf Förster <toralf.foerster@....de>
To:	Richard Weinberger <richard@....at>
CC:	Konstantin Khlebnikov <koct9i@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	UML devel <user-mode-linux-devel@...ts.sourceforge.net>
Subject: Re: [uml-devel] fuzz tested 32 bit user mode linux image hangs in
 radix_tree_next_chunk()

On 11/06/2013 10:31 PM, Richard Weinberger wrote:
> Am 06.11.2013 22:18, schrieb Toralf Förster:
>> 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 :
> 
> Can you please ask gdb for the value of offset?
> 
> Thanks,
> //richard
> 

Still trying to get those values. One attempt to do that was to replace -O2 with -O0 in the Makefile,
but that resulted into this error :

  LD      kernel/built-in.o
  CC      mm/memory.o
In function ‘zap_pmd_range’,
    inlined from ‘zap_pud_range’ at mm/memory.c:1265:8,
    inlined from ‘unmap_page_range’ at mm/memory.c:1290:8:
mm/memory.c:1220:23: error: call to ‘__compiletime_assert_1220’ declared with attribute error: BUILD_BUG failed
mm/memory.c: In function ‘follow_page_mask’:
mm/memory.c:1530:18: error: call to ‘__compiletime_assert_1530’ declared with attribute error: BUILD_BUG failed
make[1]: *** [mm/memory.o] Error 1
make: *** [mm] Error 2


With -O1 it compiled at least.


>>
>> 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 Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3
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