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Date: Mon, 27 Feb 2017 12:43:06 -0800
From: Kees Cook <keescook@...omium.org>
To: kernel-hardening@...ts.openwall.com
Cc: Kees Cook <keescook@...omium.org>,
Mark Rutland <mark.rutland@....com>,
Andy Lutomirski <luto@...nel.org>,
Hoeun Ryu <hoeun.ryu@...il.com>,
PaX Team <pageexec@...email.hu>,
Emese Revfy <re.emese@...il.com>,
Russell King <linux@...linux.org.uk>,
x86@...nel.org
Subject: [RFC][PATCH 8/8] cgroups: force all struct cftype const
As found in PaX, mark struct cftype with __do_const and add helpers
to deal with rare writes. This is a more complex example of a write-rarely
structure, which needs to use list helpers and blocks of enable/disable
pairs to perform the needed updates.
Signed-off-by: Kees Cook <keescook@...omium.org>
---
include/linux/cgroup-defs.h | 2 +-
kernel/cgroup.c | 35 +++++++++++++++++++++++------------
2 files changed, 24 insertions(+), 13 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 861b4677fc5b..aa15b3132bce 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -431,7 +431,7 @@ struct cftype {
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lock_class_key lockdep_key;
#endif
-};
+} __do_const;
/*
* Control Group subsystem type.
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b794bcadefa4..19a8e1baeb6b 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3653,11 +3653,11 @@ static int cgroup_add_file(struct cgroup_subsys_state *css, struct cgroup *cgrp,
int ret;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
- key = &cft->lockdep_key;
+ key = (struct lock_class_key *)&cft->lockdep_key;
#endif
kn = __kernfs_create_file(cgrp->kn, cgroup_file_name(cgrp, cft, name),
- cgroup_file_mode(cft), 0, cft->kf_ops, cft,
- NULL, key);
+ cgroup_file_mode(cft), 0, cft->kf_ops,
+ (void *)cft, NULL, key);
if (IS_ERR(kn))
return PTR_ERR(kn);
@@ -3760,11 +3760,16 @@ static void cgroup_exit_cftypes(struct cftype *cfts)
/* free copy for custom atomic_write_len, see init_cftypes() */
if (cft->max_write_len && cft->max_write_len != PAGE_SIZE)
kfree(cft->kf_ops);
- cft->kf_ops = NULL;
- cft->ss = NULL;
+
+ rare_write_enable();
+ __rare_write(cft->kf_ops, NULL);
+ __rare_write(cft->ss, NULL);
/* revert flags set by cgroup core while adding @cfts */
- cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);
+ __rare_write(cft->flags,
+ cft->flags & ~(__CFTYPE_ONLY_ON_DFL |
+ __CFTYPE_NOT_ON_DFL));
+ rare_write_disable();
}
}
@@ -3795,8 +3800,10 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
kf_ops->atomic_write_len = cft->max_write_len;
}
- cft->kf_ops = kf_ops;
- cft->ss = ss;
+ rare_write_enable();
+ __rare_write(cft->kf_ops, kf_ops);
+ __rare_write(cft->ss, ss);
+ rare_write_disable();
}
return 0;
@@ -3809,7 +3816,7 @@ static int cgroup_rm_cftypes_locked(struct cftype *cfts)
if (!cfts || !cfts[0].ss)
return -ENOENT;
- list_del(&cfts->node);
+ rare_list_del(&cfts->node);
cgroup_apply_cftypes(cfts, false);
cgroup_exit_cftypes(cfts);
return 0;
@@ -3866,7 +3873,7 @@ static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
mutex_lock(&cgroup_mutex);
- list_add_tail(&cfts->node, &ss->cfts);
+ rare_list_add_tail(&cfts->node, &ss->cfts);
ret = cgroup_apply_cftypes(cfts, true);
if (ret)
cgroup_rm_cftypes_locked(cfts);
@@ -3887,8 +3894,10 @@ int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
+ rare_write_enable();
for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
- cft->flags |= __CFTYPE_ONLY_ON_DFL;
+ __rare_write(cft->flags, cft->flags | __CFTYPE_ONLY_ON_DFL);
+ rare_write_disable();
return cgroup_add_cftypes(ss, cfts);
}
@@ -3904,8 +3913,10 @@ int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
{
struct cftype *cft;
+ rare_write_enable();
for (cft = cfts; cft && cft->name[0] != '\0'; cft++)
- cft->flags |= __CFTYPE_NOT_ON_DFL;
+ __rare_write(cft->flags, cft->flags | __CFTYPE_NOT_ON_DFL);
+ rare_write_disable();
return cgroup_add_cftypes(ss, cfts);
}
--
2.7.4
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