Commit f9ab5b5b authored Jun 17, 2009 by Li Zefan Committed by Linus Torvalds Jun 18, 2009

cgroups: forbid noprefix if mounting more than just cpuset subsystem



The 'noprefix' option was introduced for backwards-compatibility of
cpuset, but actually it can be used when mounting other subsystems.

This results in possibility of name collision, and now the collision can
really happen, because we have 'stat' file in both memory and cpuacct
subsystem:

	# mount -t cgroup -o noprefix,memory,cpuacct xxx /mnt

Cgroup will happily mount the 2 subsystems, but only 'stat' file of memory
subsys can be seen.

We don't want users to use nopreifx, and also want to avoid name
collision, so we change to allow noprefix only if mounting just the cpuset
subsystem.

[akpm@linux-foundation.org: fix shift for cpuset_subsys_id >= 32]
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 8ca739e3

kernel/cgroup.c

+14 −0

Original line number	Diff line number	Diff line
		@@ -843,6 +843,11 @@ static int parse_cgroupfs_options(char *data,
		struct cgroup_sb_opts *opts)
		{
		char token, o = data ?: "all";
		unsigned long mask = (unsigned long)-1;

		#ifdef CONFIG_CPUSETS
		mask = ~(1UL << cpuset_subsys_id);
		#endif

		opts->subsys_bits = 0;
		opts->flags = 0;
		@@ -887,6 +892,15 @@ static int parse_cgroupfs_options(char *data,
		}
		}

		/*
		* Option noprefix was introduced just for backward compatibility
		* with the old cpuset, so we allow noprefix only if mounting just
		* the cpuset subsystem.
		*/
		if (test_bit(ROOT_NOPREFIX, &opts->flags) &&
		(opts->subsys_bits & mask))
		return -EINVAL;

		/* We can't have an empty hierarchy */
		if (!opts->subsys_bits)
		return -EINVAL;