I was able to reproduce this on -42.el5.

GFS2: can't parse mount arguments
BUG: unable to handle kernel NULL pointer dereference at virtual address 0000062c
 printing eip:
c0438933
*pde = e6e55067
Oops: 0002 [#1]
SMP 
last sysfs file: /fs/gfs2/morph-cluster:morph-cluster8/lock_module/block
Modules linked in: gnbd(U) lock_nolock gfs(U) lock_dlm gfs2 dlm configfs autofs4
hidp rfcomm l2cap bluetooth sunrpc ipv6 dm_multipath video sbs backlight i2c_ec
button battery asus_acpi ac lp parport_pc i2c_i801 floppy parport ide_cd
intel_rng i2c_core e7xxx_edac sg cdrom edac_mc e1000 pcspkr dm_snapshot dm_zero
dm_mirror dm_mod qla2xxx scsi_transport_fc ata_piix libata sd_mod scsi_mod ext3
jbd ehci_hcd ohci_hcd uhci_hcd
CPU:    1
EIP:    0060:[<c0438933>]    Not tainted VLI
EFLAGS: 00010246   (2.6.18-42.el5 #1) 
EIP is at down_write+0xf/0x19
eax: 0000062c   ebx: 0000062c   ecx: f7aa1740   edx: ffff0001
esi: 00000000   edi: 0000062c   ebp: f6099280   esp: ea845d60
ds: 007b   es: 007b   ss: 0068
Process mount.gfs2 (pid: 6315, ti=ea845000 task=f7529550 task.ti=ea845000)
Stack: 00000000 f8d34b34 c327e23c f8d55060 00000000 f8d55060 c327e200 f6099280 
       f8d34de3 c327e200 f8d39cbd c327e200 c047574b ffffffea 00000000 c0475d2b 
       332d6d64 f7850600 c0678c80 000080d0 c0678c80 f7529550 c0458d4e 00000044 
Call Trace:
 [<f8d34b34>] gfs2_log_flush+0x18/0x2bd [gfs2]
 [<f8d34de3>] gfs2_meta_syncfs+0xa/0x31 [gfs2]
 [<f8d39cbd>] gfs2_kill_sb+0x19/0x21 [gfs2]
 [<c047574b>] deactivate_super+0x52/0x65
 [<c0475d2b>] get_sb_bdev+0xdb/0x110
 [<c0458d4e>] __alloc_pages+0x57/0x282
 [<f8d39cd9>] gfs2_get_sb+0x14/0x30 [gfs2]
 [<f8d3a945>] fill_super+0x0/0x51a [gfs2]
 [<c04757db>] vfs_kern_mount+0x7d/0xf2
 [<c0475882>] do_kern_mount+0x25/0x36
 [<c04883c2>] do_mount+0x5d6/0x646
 [<c0436025>] autoremove_wake_function+0x0/0x2d
 [<c05a2fd8>] do_sock_read+0xae/0xb7
 [<c05a356b>] sock_aio_read+0x53/0x61
 [<c0458a7d>] get_page_from_freelist+0x96/0x310
 [<c0487357>] copy_mount_options+0xaa/0x109
 [<c048849f>] sys_mount+0x6d/0xa5
 [<c0404eff>] syscall_call+0x7/0xb
 =======================
Code: 0f c1 10 78 41 c3 ba ff ff 00 00 f0 0f c1 10 75 42 c3 f0 81 00 00 00 01 00
78 45 c3 53 89 c3 e8 02 b7 1c 00 ba 01 00 ff ff 89 d8 <f0> 0f c1 10 85 d2 75 38
5b c3 53 89 c3 e8 e9 b6 1c 00 89 d8 f0 
EIP: [<c0438933>] down_write+0xf/0x19 SS:ESP 0068:ea845d60
 <0>Kernel panic - not syncing: Fatal exception

Created attachment 164441 [details]
check for NULL sdp in gfs2_kill_sb

This patch should fix the problem. Basically, when you try to mount gfs2 with
-o garbage, the mount fails and the gfs2 superblock is deallocated and becomes
NULL. The vfs comes around later on and calls gfs2_kill_sb. At this point the
hidden gfs2 superblock pointer (sb->s_fs_info) is NULL and dereferencing it
through gfs2_meta_syncfs causes the panic. (the other function call to
gfs2_delete_debugfs_file() succeeds because this function already checks for a
NULL pointer)

Tested and verified against kernel-2.6.18-43.gfs2abhi.001.

Changing summary so that it's not confused with other bug #253289

Posted fix to rhkernel-list:
http://post-office.corp.redhat.com/archives/rhkernel-list/2007-August/msg00826.html

in 2.6.18-44.el5
You can download this test kernel from http://people.redhat.com/dzickus/el5

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on the solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHBA-2007-0959.html