Re: 2.6.23-rc1-mm1 - loopback mount of files fails loop-use-unlocked_ioctl.patch

Valdis.Kletnieks
2007-08-01T16:14:20Z

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On Wed, 25 Jul 2007 04:03:04 PDT, Andrew Morton said:

> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.23-rc1/2.6.23-rc1-mm1/

Looks like -rc1-mm2 came out while I was hunting this, haven't tried that yet)

File-backed loopback seems to be broken (note that I use a LVM volume with
a 'mount -o loop,encryption=aes /dev/mapper/...' every day - that *does* work).

loop-use-unlocked_ioctl.patch is the offender after bisecting.

I had created an ISO image with genisoimage, and to test it, I had done:

mount -o loop.ro /path/to/temp.iso /mnt

(Note that the image itself is good - I burned it to a CD, and then
'mount /dev/cdrom /mnt' worked just fine, so it's definitely the loopback,
and on file-backed mounts...).

and got treated to this wonderful oops:

[ 170.420603] Unable to handle kernel NULL pointer dereference at 00000000000000b8 RIP:
[ 170.420877] [<ffffffff803bf9b1>] lo_ioctl+0x21/0x94a
[ 170.421243] PGD 41c5067 PUD 6111067 PMD 0
[ 170.421464] Oops: 0000 [1] PREEMPT SMP
[ 170.421671] CPU 0
[ 170.421775] Modules linked in: sha256 aes video output thermal processor fan container button bay battery ac nvram pcmcia firmware_class ohci1394 yenta_socket ieee1394 rsrc_nonstatic iTCO_wdt pcmcia_core iTCO_vendor_support intel_agp rtc
[ 170.422989] Pid: 1616, comm: mount Not tainted 2.6.23-rc1 #3
[ 170.423254] RIP: 0010:[<ffffffff803bf9b1>] [<ffffffff803bf9b1>] lo_ioctl+0x21/0x94a
[ 170.423627] RSP: 0018:ffff8100047076d8 EFLAGS: 00010296
[ 170.423876] RAX: ffffffff80698720 RBX: 00000000fffffdfd RCX: ffffffff803bf990
[ 170.424210] RDX: ffff810004707b18 RSI: 0000000000005310 RDI: 0000000000000000
[ 170.424544] RBP: ffff8100047078d8 R08: ffff810004707b18 R09: ffff810004707968
[ 170.424878] R10: ffff810004707b18 R11: ffff810004707b18 R12: 0000000000005310
[ 170.425212] R13: ffff810004707b18 R14: ffff810004707b18 R15: 0000000000000000
[ 170.425547] FS: 00002b82792a4740(0000) GS:ffffffff806e1000(0000) knlGS:0000000000000000
[ 170.425928] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 170.426197] CR2: 00000000000000b8 CR3: 000000000610b000 CR4: 00000000000006e0
[ 170.426531] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[ 170.439502] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
[ 170.452460] Process mount (pid: 1616, threadinfo ffff810004706000, task ffff810006898800)
[ 170.465758] Stack: 0000003900000044 ffff810006898800 0000000000000000 ffff810006812588
[ 170.479365] 0000000005071980 0000000000000007 0000000000000000 0000000000000044
[ 170.493151] 0000000000100000 ffff8100047077b8 ffff8100047077a8 ffffffff8031facb
[ 170.493517] Call Trace:
[ 170.520574] [<ffffffff8031facb>] avc_has_perm+0x4c/0x5e
[ 170.534308] [<ffffffff80320994>] inode_has_perm+0x6b/0x7a
[ 170.547974] [<ffffffff8029c126>] __d_lookup+0xe1/0x154
[ 170.561721] [<ffffffff80346bf7>] kobject_get+0x1a/0x21
[ 170.575187] [<ffffffff8033e29c>] get_disk+0x8d/0xad
[ 170.588601] [<ffffffff8033e2c8>] exact_lock+0xc/0x14
[ 170.601969] [<ffffffff803bc688>] kobj_lookup+0x14d/0x183
[ 170.615253] [<ffffffff8033d5e2>] blkdev_driver_ioctl+0x39/0x78
[ 170.628545] [<ffffffff8033dc7c>] blkdev_ioctl+0x65b/0x6b7
[ 170.641836] [<ffffffff802b082a>] __blkdev_get+0x7b/0x8d
[ 170.655105] [<ffffffff802b0a65>] ioctl_by_bdev+0x34/0x48
[ 170.668432] [<ffffffff802fbcff>] isofs_fill_super+0x337/0xa68
[ 170.681666] [<ffffffff80519ec2>] __down_write_nested+0x3d/0xab
[ 170.694896] [<ffffffff80519f3b>] __down_write+0xb/0xd
[ 170.707835] [<ffffffff8028c412>] sget+0x374/0x386
[ 170.720528] [<ffffffff8028bec8>] set_bdev_super+0x0/0x14
[ 170.733267] [<ffffffff8028cfbb>] get_sb_bdev+0x109/0x157
[ 170.745881] [<ffffffff802fb9c8>] isofs_fill_super+0x0/0xa68
[ 170.758382] [<ffffffff802fb445>] isofs_get_sb+0x13/0x15
[ 170.770713] [<ffffffff8028cac2>] vfs_kern_mount+0x90/0x11a
[ 170.782999] [<ffffffff8028cba5>] do_kern_mount+0x47/0xe2
[ 170.795245] [<ffffffff802a1d70>] do_mount+0x691/0x704
[ 170.807349] [<ffffffff802a06cb>] mntput_no_expire+0x1e/0x98
[ 170.819351] [<ffffffff80294b13>] link_path_walk+0xe8/0xfc
[ 170.831216] [<ffffffff802b0232>] bdput+0xd/0xf
[ 170.843065] [<ffffffff802a06cb>] mntput_no_expire+0x1e/0x98
[ 170.854874] [<ffffffff80294b43>] path_walk+0x1c/0x1e
[ 170.866566] [<ffffffff80294e38>] do_path_lookup+0x1b6/0x22f
[ 170.878247] [<ffffffff802937a1>] putname+0x37/0x39
[ 170.889781] [<ffffffff802957a1>] __user_walk_fd+0x4c/0x5c
[ 170.901309] [<ffffffff8026e055>] __alloc_pages+0x5c/0x2b5
[ 170.912789] [<ffffffff802a06cb>] mntput_no_expire+0x1e/0x98
[ 170.924359] [<ffffffff802a1e6c>] sys_mount+0x89/0xcb
[ 170.935859] [<ffffffff8023ea8b>] sys_rt_sigprocmask+0x58/0xd7
[ 170.947361] [<ffffffff8020bece>] system_call+0x7e/0x83
[ 170.958877]
[ 170.970241]
[ 170.970241] Code: 48 8b 87 b8 00 00 00 48 8b 18 48 8b 83 e8 01 00 00 48 8b 80
[ 170.993080] RIP [<ffffffff803bf9b1>] lo_ioctl+0x21/0x94a
[ 171.004333] RSP <ffff8100047076d8>
[ 171.015387] CR2: 00000000000000b8
[ 171.029069] mount used greatest stack depth: 3304 bytes left

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