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From: Kees Cook <keescook@chromium.org>
To: kernel-hardening@lists.openwall.com
Cc: Kees Cook <keescook@chromium.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Andy Lutomirski <luto@kernel.org>,
	Hoeun Ryu <hoeun.ryu@gmail.com>, PaX Team <pageexec@freemail.hu>,
	Emese Revfy <re.emese@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: [RFC v2][PATCH 11/11] cgroups: force all struct cftype const
Date: Wed, 29 Mar 2017 11:16:03 -0700
Message-ID: <1490811363-93944-12-git-send-email-keescook@chromium.org> (raw)
In-Reply-To: <1490811363-93944-1-git-send-email-keescook@chromium.org>

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 begin/end pairs
to perform the needed updates.

With this change and the constify plugin enabled, the before/after
section byte sizes show:

before:
    rodata: 0x2cc2f0
    data:   0x130d00

after:
    rodata: 0x2cf2f0 (+74478)
    data:   0x12e5c0 (-65710)

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 include/linux/cgroup-defs.h |  2 +-
 kernel/cgroup/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 6a3f850cabab..67563a80d01f 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -434,7 +434,7 @@ 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/cgroup.c b/kernel/cgroup/cgroup.c
index 48851327a15e..94188df45f96 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3058,11 +3058,11 @@ 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);
 
@@ -3165,11 +3165,16 @@ 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_begin();
+		__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_end();
 	}
 }
 
@@ -3200,8 +3205,10 @@ 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_begin();
+		__rare_write(cft->kf_ops, kf_ops);
+		__rare_write(cft->ss, ss);
+		rare_write_end();
 	}
 
 	return 0;
@@ -3214,7 +3221,7 @@ 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;
@@ -3271,7 +3278,7 @@ 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);
@@ -3292,8 +3299,10 @@ int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
 	struct cftype *cft;
 
+	rare_write_begin();
 	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_end();
 	return cgroup_add_cftypes(ss, cfts);
 }
 
@@ -3309,8 +3318,10 @@ int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
 	struct cftype *cft;
 
+	rare_write_begin();
 	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_end();
 	return cgroup_add_cftypes(ss, cfts);
 }
 
-- 
2.7.4

  parent reply index

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-29 18:15 [RFC v2] Introduce rare_write() infrastructure Kees Cook
2017-03-29 18:15 ` [RFC v2][PATCH 01/11] " Kees Cook
2017-03-29 18:23   ` Kees Cook
2017-03-30  7:44     ` Ho-Eun Ryu
2017-03-30 17:02       ` Kees Cook
2017-04-07  8:09   ` Ho-Eun Ryu
2017-04-07 20:38     ` Kees Cook
2017-03-29 18:15 ` [RFC v2][PATCH 02/11] lkdtm: add test for " Kees Cook
2017-03-30  9:34   ` [kernel-hardening] " Ian Campbell
2017-03-30 16:16     ` Kees Cook
2017-03-29 18:15 ` [RFC v2][PATCH 03/11] net: switch sock_diag handlers to rare_write() Kees Cook
2017-03-29 18:15 ` [RFC v2][PATCH 04/11] x86: Implement __arch_rare_write_begin/unmap() Kees Cook
2017-03-29 22:38   ` Andy Lutomirski
2017-03-30  1:41     ` Kees Cook
2017-04-05 23:57       ` Andy Lutomirski
2017-04-06  0:14         ` Kees Cook
2017-04-06 15:59           ` Andy Lutomirski
2017-04-07  8:34             ` [kernel-hardening] " Mathias Krause
2017-04-07  9:46               ` Thomas Gleixner
2017-04-07 10:51                 ` Mathias Krause
2017-04-07 13:14                   ` Thomas Gleixner
2017-04-07 13:30                     ` Mathias Krause
2017-04-07 16:14                       ` Andy Lutomirski
2017-04-07 16:22                         ` Mark Rutland
2017-04-07 19:58                         ` PaX Team
2017-04-08  4:58                           ` Andy Lutomirski
2017-04-09 12:47                             ` PaX Team
2017-04-10  0:10                               ` Andy Lutomirski
2017-04-10 10:42                                 ` PaX Team
2017-04-10 16:01                                   ` Andy Lutomirski
2017-04-07 20:44                         ` Thomas Gleixner
2017-04-07 21:20                           ` Kees Cook
2017-04-08  4:12                             ` Daniel Micay
2017-04-08  4:13                               ` Daniel Micay
2017-04-08  4:21                         ` Daniel Micay
2017-04-08  5:07                           ` Andy Lutomirski
2017-04-08  7:33                             ` Daniel Micay
2017-04-08 15:20                               ` Andy Lutomirski
2017-04-09 10:53                                 ` Ingo Molnar
2017-04-10 10:22                                 ` Mark Rutland
2017-04-09 20:24                             ` PaX Team
2017-04-10  0:31                               ` Andy Lutomirski
2017-04-10 19:47                                 ` PaX Team
2017-04-10 20:27                                   ` Andy Lutomirski
2017-04-10 20:13                               ` Kees Cook
2017-04-10 20:17                                 ` Andy Lutomirski
2017-04-07 19:25                       ` Thomas Gleixner
2017-04-07 14:45                   ` Peter Zijlstra
2017-04-10 10:29                     ` Mark Rutland
2017-04-07 19:52                 ` PaX Team
2017-04-10  8:26                   ` Thomas Gleixner
2017-04-10 19:55                     ` PaX Team
2017-04-07  9:37   ` Peter Zijlstra
2017-03-29 18:15 ` [RFC v2][PATCH 05/11] ARM: mm: dump: Add domain to output Kees Cook
2017-03-29 18:15 ` [RFC v2][PATCH 06/11] ARM: domains: Extract common USER domain init Kees Cook
2017-03-29 18:15 ` [RFC v2][PATCH 07/11] ARM: mm: set DOMAIN_WR_RARE for rodata Kees Cook
2017-03-29 18:16 ` [RFC v2][PATCH 08/11] ARM: Implement __arch_rare_write_begin/end() Kees Cook
2017-04-07  9:36   ` Peter Zijlstra
2017-03-29 18:16 ` [RFC v2][PATCH 09/11] list: add rare_write() list helpers Kees Cook
2017-03-29 18:16 ` [RFC v2][PATCH 10/11] gcc-plugins: Add constify plugin Kees Cook
2017-03-29 18:16 ` Kees Cook [this message]
2017-03-29 19:00 ` [RFC v2] Introduce rare_write() infrastructure Russell King - ARM Linux
2017-03-29 19:14   ` Kees Cook

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