unused swap offset / bad page map.

From: Dave Jones
Date: Wed Aug 07 2013 - 01:52:14 EST

Seen while fuzzing with lots of child processes.

swap_free: Unused swap offset entry 001263f5
BUG: Bad page map in process trinity-child29 pte:24c7ea00 pmd:09fec067
addr:00007f9db958d000 vm_flags:00100073 anon_vma:ffff88022c004ba0 mapping: (null) index:f99
Modules linked in: fuse ipt_ULOG snd_seq_dummy tun sctp scsi_transport_iscsi can_raw can_bcm rfcomm bnep nfnetlink hidp appletalk bluetooth rose can af_802154 phonet x25 af_rxrpc llc2 nfc rfkill af_key pppoe rds pppox ppp_generic slhc caif_socket caif irda crc_ccitt atm netrom ax25 ipx p8023 psnap p8022 llc snd_hda_codec_realtek pcspkr usb_debug snd_seq snd_seq_device snd_hda_intel snd_hda_codec snd_hwdep e1000e snd_pcm ptp pps_core snd_page_alloc snd_timer snd soundcore xfs libcrc32c
CPU: 1 PID: 2624 Comm: trinity-child29 Not tainted 3.11.0-rc4+ #1
0000000000000000 ffff8801fd7ddc90 ffffffff81700f2c 00007f9db958d000
ffff8801fd7ddcd8 ffffffff8117cba7 0000000024c7ea00 0000000000000f99
00007f9db9600000 ffff880009fecc68 0000000024c7ea00 ffff8801fd7dde00
Call Trace:
[<ffffffff81700f2c>] dump_stack+0x4e/0x82
[<ffffffff8117cba7>] print_bad_pte+0x187/0x220
[<ffffffff8117e415>] unmap_single_vma+0x535/0x890
[<ffffffff8117f719>] unmap_vmas+0x49/0x90
[<ffffffff81187ef1>] exit_mmap+0xc1/0x170
[<ffffffff810510ef>] mmput+0x6f/0x100
[<ffffffff81055818>] do_exit+0x288/0xcd0
[<ffffffff810c1da5>] ? trace_hardirqs_on_caller+0x115/0x1e0
[<ffffffff810c1e7d>] ? trace_hardirqs_on+0xd/0x10
[<ffffffff810575dc>] do_group_exit+0x4c/0xc0
[<ffffffff81057664>] SyS_exit_group+0x14/0x20
[<ffffffff81713dd4>] tracesys+0xdd/0xe2

There were a slew of these. same trace, different addr/anon_vma/index.
mapping always null.

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