Commit 579035dc authored Sep 17, 2012 by Andrew Vagin Committed by Linus Torvalds Sep 17, 2012

pid-namespace: limit value of ns_last_pid to (0, max_pid)



The kernel doesn't check the pid for negative values, so if you try to
write -2 to /proc/sys/kernel/ns_last_pid, you will get a kernel panic.

The crash happens because the next pid is -1, and alloc_pidmap() will
try to access to a nonexistent pidmap.

  map = &pid_ns->pidmap[pid/BITS_PER_PAGE];

Signed-off-by: Andrew Vagin <avagin@openvz.org>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 35c448a8

kernel/pid_namespace.c

+5 −1

Original line number	Diff line number	Diff line
		@@ -232,15 +232,19 @@ static int pid_ns_ctl_handler(struct ctl_table *table, int write,
		*/

		tmp.data = &current->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,
		},
		{ }
		};

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