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Commit 32a8cf23 authored by Daniel Lezcano's avatar Daniel Lezcano Committed by Linus Torvalds
Browse files

cgroup: make the mount options parsing more accurate 



Current behavior:
=================

(1) When we mount a cgroup, we can specify the 'all' option which
    means to enable all the cgroup subsystems.  This is the default option
    when no option is specified.

(2) If we want to mount a cgroup with a subset of the supported cgroup
    subsystems, we have to specify a subsystems name list for the mount
    option.

(3) If we specify another option like 'noprefix' or 'release_agent',
    the actual code wants the 'all' or a subsystem name option specified
    also.  Not critical but a bit not friendly as we should assume (1) in
    this case.

(4) Logically, the 'all' option is mutually exclusive with a subsystem
    name, but this is not detected.

In other words:
 succeed : mount -t cgroup -o all,freezer cgroup /cgroup
	=> is it 'all' or 'freezer' ?
 fails : mount -t cgroup -o noprefix cgroup /cgroup
	=> succeed if we do '-o noprefix,all'

The following patches consolidate a bit the mount options check.

New behavior:
=============

(1) untouched
(2) untouched
(3) the 'all' option will be by default when specifying other than
    a subsystem name option
(4) raises an error

In other words:
 fails   : mount -t cgroup -o all,freezer cgroup /cgroup
 succeed : mount -t cgroup -o noprefix cgroup /cgroup

For the sake of lisibility, the if ... then ... else ... if ...
indentation when parsing the options has been changed to:
if ... then
	...
	continue
fi

Signed-off-by: default avatarDaniel Lezcano <daniel.lezcano@free.fr>
Signed-off-by: default avatarSerge E. Hallyn <serge.hallyn@canonical.com>
Reviewed-by: default avatarLi Zefan <lizf@cn.fujitsu.com>
Reviewed-by: default avatarPaul Menage <menage@google.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Jamal Hadi Salim <hadi@cyberus.ca>
Cc: Matt Helsley <matthltc@us.ibm.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 97978e6d

kernel/cgroup.c

+60 −30
Original line number Diff line number Diff line
@@ -1074,7 +1074,8 @@ struct cgroup_sb_opts { 
 */

static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)

{

	char *token, *o = data ?: "all";

	char *token, *o = data;

	bool all_ss = false, one_ss = false;

	unsigned long mask = (unsigned long)-1;

	int i;

	bool module_pin_failed = false;
@@ -1090,24 +1091,27 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) 
	while ((token = strsep(&o, ",")) != NULL) {

		if (!*token)

			return -EINVAL;

		if (!strcmp(token, "none")) {

			/* Explicitly have no subsystems */

			opts->none = true;

			continue;

		}

		if (!strcmp(token, "all")) {

			/* Add all non-disabled subsystems */

			opts->subsys_bits = 0;

			for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {

				struct cgroup_subsys *ss = subsys[i];

				if (ss == NULL)

			/* Mutually exclusive option 'all' + subsystem name */

			if (one_ss)

				return -EINVAL;

			all_ss = true;

			continue;

				if (!ss->disabled)

					opts->subsys_bits |= 1ul << i;

		}

		} else if (!strcmp(token, "none")) {

			/* Explicitly have no subsystems */

			opts->none = true;

		} else if (!strcmp(token, "noprefix")) {

		if (!strcmp(token, "noprefix")) {

			set_bit(ROOT_NOPREFIX, &opts->flags);

		} else if (!strcmp(token, "clone_children")) {

			continue;

		}

		if (!strcmp(token, "clone_children")) {

			opts->clone_children = true;

		} else if (!strncmp(token, "release_agent=", 14)) {

			continue;

		}

		if (!strncmp(token, "release_agent=", 14)) {

			/* Specifying two release agents is forbidden */

			if (opts->release_agent)

				return -EINVAL;
@@ -1115,7 +1119,9 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) 
				kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);

			if (!opts->release_agent)

				return -ENOMEM;

		} else if (!strncmp(token, "name=", 5)) {

			continue;

		}

		if (!strncmp(token, "name=", 5)) {

			const char *name = token + 5;

			/* Can't specify an empty name */

			if (!strlen(name))
@@ -1137,21 +1143,45 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) 
					      GFP_KERNEL);

			if (!opts->name)

				return -ENOMEM;

		} else {

			struct cgroup_subsys *ss;



			continue;

		}



		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {

				ss = subsys[i];

			struct cgroup_subsys *ss = subsys[i];

			if (ss == NULL)

				continue;

				if (!strcmp(token, ss->name)) {

					if (!ss->disabled)

			if (strcmp(token, ss->name))

				continue;

			if (ss->disabled)

				continue;



			/* Mutually exclusive option 'all' + subsystem name */

			if (all_ss)

				return -EINVAL;

			set_bit(i, &opts->subsys_bits);

			one_ss = true;



			break;

		}

			}

		if (i == CGROUP_SUBSYS_COUNT)

			return -ENOENT;

	}



	/*

	 * If the 'all' option was specified select all the subsystems,

	 * otherwise 'all, 'none' and a subsystem name options were not

	 * specified, let's default to 'all'

	 */

	if (all_ss || (!all_ss && !one_ss && !opts->none)) {

		for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {

			struct cgroup_subsys *ss = subsys[i];

			if (ss == NULL)

				continue;

			if (ss->disabled)

				continue;

			set_bit(i, &opts->subsys_bits);

		}

	}



	/* Consistency checks */