* [PATCH] kernel: limit a value of ns_last_pid to (0, max_pid)
@ 2012-09-04 8:17 Andrew Vagin
2012-09-04 16:04 ` Oleg Nesterov
0 siblings, 1 reply; 2+ messages in thread
From: Andrew Vagin @ 2012-09-04 8:17 UTC (permalink / raw)
To: Andrew Morton
Cc: criu, linux-kernel, avagin, Andrew Morton, Oleg Nesterov,
Eric W. Biederman, Pavel Emelyanov
The kernel doesn't check pid on a negative values, so if
you would try to write -2 in /proc/sys/kernel/ns_last_pid,
you will get a kernel panic.
In this case the next pid is -1, and alloc_pidmap will try to access
to a nonexistent pidmap.
map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrew Vagin <avagin@openvz.org>
---
kernel/pid_namespace.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index b3c7fd5..6144bab 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -232,15 +232,19 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write,
*/
tmp.data = ¤t->nsproxy->pid_ns->last_pid;
- return proc_dointvec(&tmp, write, buffer, lenp, ppos);
+ return proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);
}
+extern int pid_max;
+static int zero = 0;
static struct ctl_table pid_ns_ctl_table[] = {
{
.procname = "ns_last_pid",
.maxlen = sizeof(int),
.mode = 0666, /* permissions are checked in the handler */
.proc_handler = pid_ns_ctl_handler,
+ .extra1 = &zero,
+ .extra2 = &pid_max,
},
{ }
};
--
1.7.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH] kernel: limit a value of ns_last_pid to (0, max_pid)
2012-09-04 8:17 [PATCH] kernel: limit a value of ns_last_pid to (0, max_pid) Andrew Vagin
@ 2012-09-04 16:04 ` Oleg Nesterov
0 siblings, 0 replies; 2+ messages in thread
From: Oleg Nesterov @ 2012-09-04 16:04 UTC (permalink / raw)
To: Andrew Vagin
Cc: Andrew Morton, criu, linux-kernel, Eric W. Biederman, Pavel Emelyanov
On 09/04, Andrew Vagin wrote:
>
> The kernel doesn't check pid on a negative values, so if
> you would try to write -2 in /proc/sys/kernel/ns_last_pid,
> you will get a kernel panic.
>
> In this case the next pid is -1, and alloc_pidmap will try to access
> to a nonexistent pidmap.
>
> map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
Yes, alloc_pidmap() assumes that pid_ns->last_pid + 1 is positive...
So ".extra1 = &zero" is not enough, INT_MAX can overflow as well.
> static struct ctl_table pid_ns_ctl_table[] = {
> {
> .procname = "ns_last_pid",
> .maxlen = sizeof(int),
> .mode = 0666, /* permissions are checked in the handler */
> .proc_handler = pid_ns_ctl_handler,
> + .extra1 = &zero,
> + .extra2 = &pid_max,
Acked-by: Oleg Nesterov <oleg@redhat.com>
^ permalink raw reply [flat|nested] 2+ messages in thread
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