From mboxrd@z Thu Jan 1 00:00:00 1970 From: Kees Cook Date: Mon, 27 Feb 2017 12:43:06 -0800 Message-Id: <1488228186-110679-9-git-send-email-keescook@chromium.org> In-Reply-To: <1488228186-110679-1-git-send-email-keescook@chromium.org> References: <1488228186-110679-1-git-send-email-keescook@chromium.org> Subject: [kernel-hardening] [RFC][PATCH 8/8] cgroups: force all struct cftype const To: kernel-hardening@lists.openwall.com Cc: Kees Cook , Mark Rutland , Andy Lutomirski , Hoeun Ryu , PaX Team , Emese Revfy , Russell King , x86@kernel.org List-ID: 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 --- 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