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authorVasily Tarasov <vtaras@openvz.org>2006-11-25 22:09:22 +0300
committerLinus Torvalds <torvalds@woody.osdl.org>2006-11-26 00:28:33 +0300
commit701e054e0c2db82359f0454c7ed4fd24346d52eb (patch)
treeaf052eb937237414705c425f08502517af52e680
parent2d51013ed2f2b6a5d2369b7fbbd989df1f6369e2 (diff)
downloadlinux-701e054e0c2db82359f0454c7ed4fd24346d52eb.tar.xz
[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>
-rw-r--r--fs/proc/base.c3
-rw-r--r--include/linux/nsproxy.h4
2 files changed, 5 insertions, 2 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 8df27401d292..795319c54f72 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -442,7 +442,8 @@ static int mountstats_open(struct inode *inode, struct file *file)
if (task) {
task_lock(task);
- namespace = task->nsproxy->namespace;
+ if (task->nsproxy)
+ namespace = task->nsproxy->namespace;
if (namespace)
get_namespace(namespace);
task_unlock(task);
diff --git a/include/linux/nsproxy.h b/include/linux/nsproxy.h
index f6baecdeecd6..971d1c6dfc4b 100644
--- a/include/linux/nsproxy.h
+++ b/include/linux/nsproxy.h
@@ -45,8 +45,10 @@ static inline void exit_task_namespaces(struct task_struct *p)
{
struct nsproxy *ns = p->nsproxy;
if (ns) {
- put_nsproxy(ns);
+ task_lock(p);
p->nsproxy = NULL;
+ task_unlock(p);
+ put_nsproxy(ns);
}
}
#endif