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Vasily Tarasov 701e054e0c [PATCH] mounstats NULL pointer dereference 
OpenVZ developers team has encountered the following problem in 2.6.19-rc6
kernel. After some seconds of running script

while [[ 1 ]]
do
	find  /proc -name mountstats | xargs cat
done

this Oops appears:

BUG: unable to handle kernel NULL pointer dereference at virtual address
00000010
 printing eip:
c01a6b70
*pde = 00000000
Oops: 0000 [#1]
SMP
Modules linked in: xt_length ipt_ttl xt_tcpmss ipt_TCPMSS iptable_mangle
iptable_filter xt_multiport xt_limit ipt_tos ipt_REJECT ip_tables x_tables
parport_pc lp parport sunrpc af_packet thermal processor fan button battery
asus_acpi ac ohci_hcd ehci_hcd usbcore i2c_nforce2 i2c_core tg3 floppy
pata_amd
ide_cd cdrom sata_nv libata
CPU:    1
EIP:    0060:[<c01a6b70>]    Not tainted VLI
EFLAGS: 00010246   (2.6.19-rc6 #2)
EIP is at mountstats_open+0x70/0xf0
eax: 00000000   ebx: e6247030   ecx: e62470f8   edx: 00000000
esi: 00000000   edi: c01a6b00   ebp: c33b83c0   esp: f4105eb4
ds: 007b   es: 007b   ss: 0068
Process cat (pid: 6044, ti=f4105000 task=f4104a70 task.ti=f4105000)
Stack: c33b83c0 c04ee940 f46a4a80 c33b83c0 e4df31b4 c01a6b00 f4105000 c0169231
       e4df31b4 c33b83c0 c33b83c0 f4105f20 00000003 f4105000 c0169445 f2503cf0
       f7f8c4c0 00008000 c33b83c0 00000000 00008000 c0169350 f4105f20 00008000
Call Trace:
 [<c01a6b00>] mountstats_open+0x0/0xf0
 [<c0169231>] __dentry_open+0x181/0x250
 [<c0169445>] nameidata_to_filp+0x35/0x50
 [<c0169350>] do_filp_open+0x50/0x60
 [<c01873d6>] seq_read+0xc6/0x300
 [<c0169511>] get_unused_fd+0x31/0xc0
 [<c01696d3>] do_sys_open+0x63/0x110
 [<c01697a7>] sys_open+0x27/0x30
 [<c01030bd>] sysenter_past_esp+0x56/0x79
 =======================
Code: 45 74 8b 54 24 20 89 44 24 08 8b 42 f0 31 d2 e8 47 cb f8 ff 85 c0 89 c3
74 51 8d 80 a0 04 00 00 e8 46 06 2c 00 8b 83 48 04 00 00 <8b> 78 10 85 ff 74
03
f0 ff 07 b0 01 86 83 a0 04 00 00 f0 ff 4b
EIP: [<c01a6b70>] mountstats_open+0x70/0xf0 SS:ESP 0068:f4105eb4

The problem is that task->nsproxy can be equal NULL for some time during
task exit. This patch fixes the BUG.

Signed-off-by: Vasily Tarasov <vtaras@openvz.org>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: "Serge E. Hallyn" <serue@us.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-11-25 13:28:33 -08:00
..
array.c [PATCH] proc: drop tasklist lock in task_state() 2006-10-02 07:57:24 -07:00
base.c [PATCH] mounstats NULL pointer dereference 2006-11-25 13:28:33 -08:00
generic.c [PATCH] mark f_ops const in the inode 2006-03-28 09:16:05 -08:00
inode-alloc.txt
inode.c Mark /proc MS_NOSUID and MS_NOEXEC 2006-07-15 12:20:05 -07:00
internal.h [PATCH] NOMMU: Implement /proc/pid/maps for NOMMU 2006-09-27 08:26:14 -07:00
kcore.c [PATCH] Kcore elf note namesz field fix 2006-09-29 09:18:25 -07:00
kmsg.c [PATCH] Make most file operations structs in fs/ const 2006-03-28 09:16:06 -08:00
Makefile [PATCH] kdump: Access dump file in elf format (/proc/vmcore) 2005-06-25 16:24:53 -07:00
mmu.c
nommu.c [PATCH] NOMMU: Implement /proc/pid/maps for NOMMU 2006-09-27 08:26:14 -07:00
proc_devtree.c [PATCH] powerpc: Cope with duplicate node & property names in /proc/device-tree 2006-03-28 16:45:23 +11:00
proc_misc.c IRQ: Maintain regs pointer globally rather than passing to IRQ handlers 2006-10-05 15:10:12 +01:00
proc_tty.c
root.c [PATCH] proc: give the root directory a task 2006-10-02 07:57:13 -07:00
task_mmu.c [PATCH] NOMMU: move the fallback arch_vma_name() to a sensible place 2006-09-27 08:26:15 -07:00
task_nommu.c [PATCH] NOMMU: Implement /proc/pid/maps for NOMMU 2006-09-27 08:26:14 -07:00
vmcore.c Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00