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* [PATCH 0/3] gcc-plugins: Introduce stackinit plugin
@ 2019-01-23 11:03 Kees Cook
  2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
                   ` (3 more replies)
  0 siblings, 4 replies; 20+ messages in thread
From: Kees Cook @ 2019-01-23 11:03 UTC (permalink / raw)
  To: linux-kernel
  Cc: Kees Cook, Ard Biesheuvel, Laura Abbott, Alexander Popov,
	xen-devel, dri-devel, intel-gfx, intel-wired-lan, netdev,
	linux-usb, linux-fsdevel, linux-mm, dev, linux-kbuild,
	linux-security-module, kernel-hardening

This adds a new plugin "stackinit" that attempts to perform unconditional
initialization of all stack variables[1]. It has wider effects than
GCC_PLUGIN_STRUCTLEAK_BYREF_ALL=y since BYREF_ALL does not consider
non-structures. A notable weakness is that padding bytes in many cases
remain uninitialized since GCC treats these bytes as "undefined". I'm
hoping we can improve the compiler (or the plugin) to cover that too.
(It's worth noting that BYREF_ALL actually does handle the padding --
I think this is due to the different method of detecting if initialization
is needed.)

Included is a tree-wide change to move switch variables up and out of
their switch and into the top-level variable declarations.

Included is a set of test cases for evaluating stack initialization,
which checks for padding, different types, etc.

Feedback welcome! :)

-Kees

[1] https://lkml.kernel.org/r/CA+55aFykZL+cSBJjBBts7ebEFfyGPdMzTmLSxKnT_29=j942dA@mail.gmail.com

Kees Cook (3):
  treewide: Lift switch variables out of switches
  gcc-plugins: Introduce stackinit plugin
  lib: Introduce test_stackinit module

 arch/x86/xen/enlighten_pv.c                   |   7 +-
 drivers/char/pcmcia/cm4000_cs.c               |   2 +-
 drivers/char/ppdev.c                          |  20 +-
 drivers/gpu/drm/drm_edid.c                    |   4 +-
 drivers/gpu/drm/i915/intel_display.c          |   2 +-
 drivers/gpu/drm/i915/intel_pm.c               |   4 +-
 drivers/net/ethernet/intel/e1000/e1000_main.c |   3 +-
 drivers/tty/n_tty.c                           |   3 +-
 drivers/usb/gadget/udc/net2280.c              |   5 +-
 fs/fcntl.c                                    |   3 +-
 lib/Kconfig.debug                             |   9 +
 lib/Makefile                                  |   1 +
 lib/test_stackinit.c                          | 327 ++++++++++++++++++
 mm/shmem.c                                    |   5 +-
 net/core/skbuff.c                             |   4 +-
 net/ipv6/ip6_gre.c                            |   4 +-
 net/ipv6/ip6_tunnel.c                         |   4 +-
 net/openvswitch/flow_netlink.c                |   7 +-
 scripts/Makefile.gcc-plugins                  |   6 +
 scripts/gcc-plugins/Kconfig                   |   9 +
 scripts/gcc-plugins/gcc-common.h              |  11 +-
 scripts/gcc-plugins/stackinit_plugin.c        |  79 +++++
 security/tomoyo/common.c                      |   3 +-
 security/tomoyo/condition.c                   |   7 +-
 security/tomoyo/util.c                        |   4 +-
 25 files changed, 484 insertions(+), 49 deletions(-)
 create mode 100644 lib/test_stackinit.c
 create mode 100644 scripts/gcc-plugins/stackinit_plugin.c

-- 
2.17.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 11:03 [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Kees Cook
@ 2019-01-23 11:03 ` Kees Cook
  2019-01-23 11:58   ` Greg KH
                     ` (2 more replies)
  2019-01-23 11:03 ` [PATCH 2/3] gcc-plugins: Introduce stackinit plugin Kees Cook
                   ` (2 subsequent siblings)
  3 siblings, 3 replies; 20+ messages in thread
From: Kees Cook @ 2019-01-23 11:03 UTC (permalink / raw)
  To: linux-kernel
  Cc: Kees Cook, Ard Biesheuvel, Laura Abbott, Alexander Popov,
	xen-devel, dri-devel, intel-gfx, intel-wired-lan, netdev,
	linux-usb, linux-fsdevel, linux-mm, dev, linux-kbuild,
	linux-security-module, kernel-hardening

Variables declared in a switch statement before any case statements
cannot be initialized, so move all instances out of the switches.
After this, future always-initialized stack variables will work
and not throw warnings like this:

fs/fcntl.c: In function ‘send_sigio_to_task’:
fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
   siginfo_t si;
             ^~

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 arch/x86/xen/enlighten_pv.c                   |  7 ++++---
 drivers/char/pcmcia/cm4000_cs.c               |  2 +-
 drivers/char/ppdev.c                          | 20 ++++++++-----------
 drivers/gpu/drm/drm_edid.c                    |  4 ++--
 drivers/gpu/drm/i915/intel_display.c          |  2 +-
 drivers/gpu/drm/i915/intel_pm.c               |  4 ++--
 drivers/net/ethernet/intel/e1000/e1000_main.c |  3 ++-
 drivers/tty/n_tty.c                           |  3 +--
 drivers/usb/gadget/udc/net2280.c              |  5 ++---
 fs/fcntl.c                                    |  3 ++-
 mm/shmem.c                                    |  5 +++--
 net/core/skbuff.c                             |  4 ++--
 net/ipv6/ip6_gre.c                            |  4 ++--
 net/ipv6/ip6_tunnel.c                         |  4 ++--
 net/openvswitch/flow_netlink.c                |  7 +++----
 security/tomoyo/common.c                      |  3 ++-
 security/tomoyo/condition.c                   |  7 ++++---
 security/tomoyo/util.c                        |  4 ++--
 18 files changed, 45 insertions(+), 46 deletions(-)

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index c54a493e139a..a79d4b548a08 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -907,14 +907,15 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
 static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 {
 	int ret;
+#ifdef CONFIG_X86_64
+	unsigned which;
+	u64 base;
+#endif
 
 	ret = 0;
 
 	switch (msr) {
 #ifdef CONFIG_X86_64
-		unsigned which;
-		u64 base;
-
 	case MSR_FS_BASE:		which = SEGBASE_FS; goto set;
 	case MSR_KERNEL_GS_BASE:	which = SEGBASE_GS_USER; goto set;
 	case MSR_GS_BASE:		which = SEGBASE_GS_KERNEL; goto set;
diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
index 7a4eb86aedac..7211dc0e6f4f 100644
--- a/drivers/char/pcmcia/cm4000_cs.c
+++ b/drivers/char/pcmcia/cm4000_cs.c
@@ -663,6 +663,7 @@ static void monitor_card(struct timer_list *t)
 {
 	struct cm4000_dev *dev = from_timer(dev, t, timer);
 	unsigned int iobase = dev->p_dev->resource[0]->start;
+	unsigned char flags0;
 	unsigned short s;
 	struct ptsreq ptsreq;
 	int i, atrc;
@@ -731,7 +732,6 @@ static void monitor_card(struct timer_list *t)
 	}
 
 	switch (dev->mstate) {
-		unsigned char flags0;
 	case M_CARDOFF:
 		DEBUGP(4, dev, "M_CARDOFF\n");
 		flags0 = inb(REG_FLAGS0(iobase));
diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
index 1ae77b41050a..d77c97e4f996 100644
--- a/drivers/char/ppdev.c
+++ b/drivers/char/ppdev.c
@@ -359,14 +359,19 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	struct pp_struct *pp = file->private_data;
 	struct parport *port;
 	void __user *argp = (void __user *)arg;
+	struct ieee1284_info *info;
+	unsigned char reg;
+	unsigned char mask;
+	int mode;
+	s32 time32[2];
+	s64 time64[2];
+	struct timespec64 ts;
+	int ret;
 
 	/* First handle the cases that don't take arguments. */
 	switch (cmd) {
 	case PPCLAIM:
 	    {
-		struct ieee1284_info *info;
-		int ret;
-
 		if (pp->flags & PP_CLAIMED) {
 			dev_dbg(&pp->pdev->dev, "you've already got it!\n");
 			return -EINVAL;
@@ -517,15 +522,6 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 
 	port = pp->pdev->port;
 	switch (cmd) {
-		struct ieee1284_info *info;
-		unsigned char reg;
-		unsigned char mask;
-		int mode;
-		s32 time32[2];
-		s64 time64[2];
-		struct timespec64 ts;
-		int ret;
-
 	case PPRSTATUS:
 		reg = parport_read_status(port);
 		if (copy_to_user(argp, &reg, sizeof(reg)))
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index b506e3622b08..8f93956c1628 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -3942,12 +3942,12 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
 		}
 
 		for_each_cea_db(cea, i, start, end) {
+			int sad_count;
+
 			db = &cea[i];
 			dbl = cea_db_payload_len(db);
 
 			switch (cea_db_tag(db)) {
-				int sad_count;
-
 			case AUDIO_BLOCK:
 				/* Audio Data Block, contains SADs */
 				sad_count = min(dbl / 3, 15 - total_sad_count);
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 3da9c0f9e948..aa1c2ebea456 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11341,6 +11341,7 @@ static bool check_digital_port_conflicts(struct drm_atomic_state *state)
 	drm_for_each_connector_iter(connector, &conn_iter) {
 		struct drm_connector_state *connector_state;
 		struct intel_encoder *encoder;
+		unsigned int port_mask;
 
 		connector_state = drm_atomic_get_new_connector_state(state, connector);
 		if (!connector_state)
@@ -11354,7 +11355,6 @@ static bool check_digital_port_conflicts(struct drm_atomic_state *state)
 		WARN_ON(!connector_state->crtc);
 
 		switch (encoder->type) {
-			unsigned int port_mask;
 		case INTEL_OUTPUT_DDI:
 			if (WARN_ON(!HAS_DDI(to_i915(dev))))
 				break;
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index a26b4eddda25..c135fdec96b3 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -478,9 +478,9 @@ static void vlv_get_fifo_size(struct intel_crtc_state *crtc_state)
 	struct vlv_fifo_state *fifo_state = &crtc_state->wm.vlv.fifo_state;
 	enum pipe pipe = crtc->pipe;
 	int sprite0_start, sprite1_start;
+	uint32_t dsparb, dsparb2, dsparb3;
 
 	switch (pipe) {
-		uint32_t dsparb, dsparb2, dsparb3;
 	case PIPE_A:
 		dsparb = I915_READ(DSPARB);
 		dsparb2 = I915_READ(DSPARB2);
@@ -1944,6 +1944,7 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
 	const struct vlv_fifo_state *fifo_state =
 		&crtc_state->wm.vlv.fifo_state;
 	int sprite0_start, sprite1_start, fifo_size;
+	uint32_t dsparb, dsparb2, dsparb3;
 
 	if (!crtc_state->fifo_changed)
 		return;
@@ -1969,7 +1970,6 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
 	spin_lock(&dev_priv->uncore.lock);
 
 	switch (crtc->pipe) {
-		uint32_t dsparb, dsparb2, dsparb3;
 	case PIPE_A:
 		dsparb = I915_READ_FW(DSPARB);
 		dsparb2 = I915_READ_FW(DSPARB2);
diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
index 8fe9af0e2ab7..041062736845 100644
--- a/drivers/net/ethernet/intel/e1000/e1000_main.c
+++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
@@ -3140,8 +3140,9 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb,
 
 		hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
 		if (skb->data_len && hdr_len == len) {
+			unsigned int pull_size;
+
 			switch (hw->mac_type) {
-				unsigned int pull_size;
 			case e1000_82544:
 				/* Make sure we have room to chop off 4 bytes,
 				 * and that the end alignment will work out to
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 5dc9686697cf..eafb39157281 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -634,6 +634,7 @@ static size_t __process_echoes(struct tty_struct *tty)
 	while (MASK(ldata->echo_commit) != MASK(tail)) {
 		c = echo_buf(ldata, tail);
 		if (c == ECHO_OP_START) {
+			unsigned int num_chars, num_bs;
 			unsigned char op;
 			int no_space_left = 0;
 
@@ -652,8 +653,6 @@ static size_t __process_echoes(struct tty_struct *tty)
 			op = echo_buf(ldata, tail + 1);
 
 			switch (op) {
-				unsigned int num_chars, num_bs;
-
 			case ECHO_OP_ERASE_TAB:
 				if (MASK(ldata->echo_commit) == MASK(tail + 2))
 					goto not_yet_stored;
diff --git a/drivers/usb/gadget/udc/net2280.c b/drivers/usb/gadget/udc/net2280.c
index e7dae5379e04..2b275a574e94 100644
--- a/drivers/usb/gadget/udc/net2280.c
+++ b/drivers/usb/gadget/udc/net2280.c
@@ -2854,16 +2854,15 @@ static void ep_clear_seqnum(struct net2280_ep *ep)
 static void handle_stat0_irqs_superspeed(struct net2280 *dev,
 		struct net2280_ep *ep, struct usb_ctrlrequest r)
 {
+	struct net2280_ep *e;
 	int tmp = 0;
+	u16 status;
 
 #define	w_value		le16_to_cpu(r.wValue)
 #define	w_index		le16_to_cpu(r.wIndex)
 #define	w_length	le16_to_cpu(r.wLength)
 
 	switch (r.bRequest) {
-		struct net2280_ep *e;
-		u16 status;
-
 	case USB_REQ_SET_CONFIGURATION:
 		dev->addressed_state = !w_value;
 		goto usb3_delegate;
diff --git a/fs/fcntl.c b/fs/fcntl.c
index 083185174c6d..0640b64ecdc2 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -725,6 +725,8 @@ static void send_sigio_to_task(struct task_struct *p,
 			       struct fown_struct *fown,
 			       int fd, int reason, enum pid_type type)
 {
+	kernel_siginfo_t si;
+
 	/*
 	 * F_SETSIG can change ->signum lockless in parallel, make
 	 * sure we read it once and use the same value throughout.
@@ -735,7 +737,6 @@ static void send_sigio_to_task(struct task_struct *p,
 		return;
 
 	switch (signum) {
-		kernel_siginfo_t si;
 		default:
 			/* Queue a rt signal with the appropriate fd as its
 			   value.  We use SI_SIGIO as the source, not 
diff --git a/mm/shmem.c b/mm/shmem.c
index 6ece1e2fe76e..0b02624dd8b2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1721,6 +1721,9 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 		swap_free(swap);
 
 	} else {
+		loff_t i_size;
+		pgoff_t off;
+
 		if (vma && userfaultfd_missing(vma)) {
 			*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
 			return 0;
@@ -1734,8 +1737,6 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
 		if (shmem_huge == SHMEM_HUGE_FORCE)
 			goto alloc_huge;
 		switch (sbinfo->huge) {
-			loff_t i_size;
-			pgoff_t off;
 		case SHMEM_HUGE_NEVER:
 			goto alloc_nohuge;
 		case SHMEM_HUGE_WITHIN_SIZE:
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 26d848484912..7597b3fc9d21 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4506,9 +4506,9 @@ static __sum16 *skb_checksum_setup_ip(struct sk_buff *skb,
 				      typeof(IPPROTO_IP) proto,
 				      unsigned int off)
 {
-	switch (proto) {
-		int err;
+	int err;
 
+	switch (proto) {
 	case IPPROTO_TCP:
 		err = skb_maybe_pull_tail(skb, off + sizeof(struct tcphdr),
 					  off + MAX_TCP_HDR_LEN);
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index b1be67ca6768..9aee1add46c0 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -427,9 +427,11 @@ static int ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		       u8 type, u8 code, int offset, __be32 info)
 {
 	struct net *net = dev_net(skb->dev);
+	struct ipv6_tlv_tnl_enc_lim *tel;
 	const struct ipv6hdr *ipv6h;
 	struct tnl_ptk_info tpi;
 	struct ip6_tnl *t;
+	__u32 teli;
 
 	if (gre_parse_header(skb, &tpi, NULL, htons(ETH_P_IPV6),
 			     offset) < 0)
@@ -442,8 +444,6 @@ static int ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 		return -ENOENT;
 
 	switch (type) {
-		struct ipv6_tlv_tnl_enc_lim *tel;
-		__u32 teli;
 	case ICMPV6_DEST_UNREACH:
 		net_dbg_ratelimited("%s: Path to destination invalid or inactive!\n",
 				    t->parms.name);
diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 0c6403cf8b52..94ccc7a9037b 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -478,10 +478,12 @@ ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,
 	struct net *net = dev_net(skb->dev);
 	u8 rel_type = ICMPV6_DEST_UNREACH;
 	u8 rel_code = ICMPV6_ADDR_UNREACH;
+	struct ipv6_tlv_tnl_enc_lim *tel;
 	__u32 rel_info = 0;
 	struct ip6_tnl *t;
 	int err = -ENOENT;
 	int rel_msg = 0;
+	__u32 mtu, teli;
 	u8 tproto;
 	__u16 len;
 
@@ -501,8 +503,6 @@ ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,
 	err = 0;
 
 	switch (*type) {
-		struct ipv6_tlv_tnl_enc_lim *tel;
-		__u32 mtu, teli;
 	case ICMPV6_DEST_UNREACH:
 		net_dbg_ratelimited("%s: Path to destination invalid or inactive!\n",
 				    t->parms.name);
diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
index 691da853bef5..dee2f9516ae8 100644
--- a/net/openvswitch/flow_netlink.c
+++ b/net/openvswitch/flow_netlink.c
@@ -2652,8 +2652,11 @@ static int validate_set(const struct nlattr *a,
 			u8 mac_proto, __be16 eth_type, bool masked, bool log)
 {
 	const struct nlattr *ovs_key = nla_data(a);
+	const struct ovs_key_ipv4 *ipv4_key;
+	const struct ovs_key_ipv6 *ipv6_key;
 	int key_type = nla_type(ovs_key);
 	size_t key_len;
+	int err;
 
 	/* There can be only one key in a action */
 	if (nla_total_size(nla_len(ovs_key)) != nla_len(a))
@@ -2671,10 +2674,6 @@ static int validate_set(const struct nlattr *a,
 		return -EINVAL;
 
 	switch (key_type) {
-	const struct ovs_key_ipv4 *ipv4_key;
-	const struct ovs_key_ipv6 *ipv6_key;
-	int err;
-
 	case OVS_KEY_ATTR_PRIORITY:
 	case OVS_KEY_ATTR_SKB_MARK:
 	case OVS_KEY_ATTR_CT_MARK:
diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
index c598aa00d5e3..bedbd0518153 100644
--- a/security/tomoyo/common.c
+++ b/security/tomoyo/common.c
@@ -1583,8 +1583,9 @@ static void tomoyo_read_domain(struct tomoyo_io_buffer *head)
 	list_for_each_cookie(head->r.domain, &tomoyo_domain_list) {
 		struct tomoyo_domain_info *domain =
 			list_entry(head->r.domain, typeof(*domain), list);
+		u8 i;
+
 		switch (head->r.step) {
-			u8 i;
 		case 0:
 			if (domain->is_deleted &&
 			    !head->r.print_this_domain_only)
diff --git a/security/tomoyo/condition.c b/security/tomoyo/condition.c
index 8d0e1b9c9c57..c10d903febe5 100644
--- a/security/tomoyo/condition.c
+++ b/security/tomoyo/condition.c
@@ -787,10 +787,11 @@ bool tomoyo_condition(struct tomoyo_request_info *r,
 		/* Check string expressions. */
 		if (right == TOMOYO_NAME_UNION) {
 			const struct tomoyo_name_union *ptr = names_p++;
+			struct tomoyo_path_info *symlink;
+			struct tomoyo_execve *ee;
+			struct file *file;
+
 			switch (left) {
-				struct tomoyo_path_info *symlink;
-				struct tomoyo_execve *ee;
-				struct file *file;
 			case TOMOYO_SYMLINK_TARGET:
 				symlink = obj ? obj->symlink_target : NULL;
 				if (!symlink ||
diff --git a/security/tomoyo/util.c b/security/tomoyo/util.c
index badffc8271c8..8e2bb36df37b 100644
--- a/security/tomoyo/util.c
+++ b/security/tomoyo/util.c
@@ -668,6 +668,8 @@ static bool tomoyo_file_matches_pattern2(const char *filename,
 {
 	while (filename < filename_end && pattern < pattern_end) {
 		char c;
+		int i, j;
+
 		if (*pattern != '\\') {
 			if (*filename++ != *pattern++)
 				return false;
@@ -676,8 +678,6 @@ static bool tomoyo_file_matches_pattern2(const char *filename,
 		c = *filename;
 		pattern++;
 		switch (*pattern) {
-			int i;
-			int j;
 		case '?':
 			if (c == '/') {
 				return false;
-- 
2.17.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH 2/3] gcc-plugins: Introduce stackinit plugin
  2019-01-23 11:03 [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Kees Cook
  2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
@ 2019-01-23 11:03 ` Kees Cook
  2019-01-23 11:03 ` [PATCH 3/3] lib: Introduce test_stackinit module Kees Cook
  2019-01-29  0:12 ` [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Alexander Popov
  3 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2019-01-23 11:03 UTC (permalink / raw)
  To: linux-kernel
  Cc: Kees Cook, Ard Biesheuvel, Laura Abbott, Alexander Popov,
	xen-devel, dri-devel, intel-gfx, intel-wired-lan, netdev,
	linux-usb, linux-fsdevel, linux-mm, dev, linux-kbuild,
	linux-security-module, kernel-hardening

This attempts to duplicate the proposed gcc option -finit-local-vars[1]
in an effort to implement the "always initialize local variables" kernel
development goal[2].

Enabling CONFIG_GCC_PLUGIN_STACKINIT should stop all "uninitialized
stack variable" flaws as long as they don't depend on being zero. :)

[1] https://gcc.gnu.org/ml/gcc-patches/2014-06/msg00615.html
[2] https://lkml.kernel.org/r/CA+55aFykZL+cSBJjBBts7ebEFfyGPdMzTmLSxKnT_29=j942dA@mail.gmail.com

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 scripts/Makefile.gcc-plugins           |  6 ++
 scripts/gcc-plugins/Kconfig            |  9 +++
 scripts/gcc-plugins/gcc-common.h       | 11 +++-
 scripts/gcc-plugins/stackinit_plugin.c | 79 ++++++++++++++++++++++++++
 4 files changed, 102 insertions(+), 3 deletions(-)
 create mode 100644 scripts/gcc-plugins/stackinit_plugin.c

diff --git a/scripts/Makefile.gcc-plugins b/scripts/Makefile.gcc-plugins
index 35042d96cf5d..2483121d781c 100644
--- a/scripts/Makefile.gcc-plugins
+++ b/scripts/Makefile.gcc-plugins
@@ -12,6 +12,12 @@ export DISABLE_LATENT_ENTROPY_PLUGIN
 
 gcc-plugin-$(CONFIG_GCC_PLUGIN_SANCOV)		+= sancov_plugin.so
 
+gcc-plugin-$(CONFIG_GCC_PLUGIN_STACKINIT)	+= stackinit_plugin.so
+ifdef CONFIG_GCC_PLUGIN_STACKINIT
+    DISABLE_STACKINIT_PLUGIN += -fplugin-arg-stackinit_plugin-disable
+endif
+export DISABLE_STACKINIT_PLUGIN
+
 gcc-plugin-$(CONFIG_GCC_PLUGIN_STRUCTLEAK)	+= structleak_plugin.so
 gcc-plugin-cflags-$(CONFIG_GCC_PLUGIN_STRUCTLEAK_VERBOSE)	\
 		+= -fplugin-arg-structleak_plugin-verbose
diff --git a/scripts/gcc-plugins/Kconfig b/scripts/gcc-plugins/Kconfig
index d45f7f36b859..b117fe83f1d3 100644
--- a/scripts/gcc-plugins/Kconfig
+++ b/scripts/gcc-plugins/Kconfig
@@ -66,6 +66,15 @@ config GCC_PLUGIN_LATENT_ENTROPY
 	   * https://grsecurity.net/
 	   * https://pax.grsecurity.net/
 
+config GCC_PLUGIN_STACKINIT
+	bool "Initialize all stack variables to zero by default"
+	depends on GCC_PLUGINS
+	depends on !GCC_PLUGIN_STRUCTLEAK
+	help
+	  This plugin zero-initializes all stack variables. This is more
+	  comprehensive than GCC_PLUGIN_STRUCTLEAK, and attempts to
+	  duplicate the proposed -finit-local-vars gcc build flag.
+
 config GCC_PLUGIN_STRUCTLEAK
 	bool "Force initialization of variables containing userspace addresses"
 	# Currently STRUCTLEAK inserts initialization out of live scope of
diff --git a/scripts/gcc-plugins/gcc-common.h b/scripts/gcc-plugins/gcc-common.h
index 552d5efd7cb7..f690b4deeabd 100644
--- a/scripts/gcc-plugins/gcc-common.h
+++ b/scripts/gcc-plugins/gcc-common.h
@@ -76,6 +76,14 @@
 #include "c-common.h"
 #endif
 
+#if BUILDING_GCC_VERSION > 4005
+#include "c-tree.h"
+#else
+/* should come from c-tree.h if only it were installed for gcc 4.5... */
+#define C_TYPE_FIELDS_READONLY(TYPE) TREE_LANG_FLAG_1(TYPE)
+extern bool global_bindings_p (void);
+#endif
+
 #if BUILDING_GCC_VERSION <= 4008
 #include "tree-flow.h"
 #else
@@ -158,9 +166,6 @@ void dump_gimple_stmt(pretty_printer *, gimple, int, int);
 #define TYPE_NAME_POINTER(node) IDENTIFIER_POINTER(TYPE_NAME(node))
 #define TYPE_NAME_LENGTH(node) IDENTIFIER_LENGTH(TYPE_NAME(node))
 
-/* should come from c-tree.h if only it were installed for gcc 4.5... */
-#define C_TYPE_FIELDS_READONLY(TYPE) TREE_LANG_FLAG_1(TYPE)
-
 static inline tree build_const_char_string(int len, const char *str)
 {
 	tree cstr, elem, index, type;
diff --git a/scripts/gcc-plugins/stackinit_plugin.c b/scripts/gcc-plugins/stackinit_plugin.c
new file mode 100644
index 000000000000..41055cd7098e
--- /dev/null
+++ b/scripts/gcc-plugins/stackinit_plugin.c
@@ -0,0 +1,79 @@
+/* SPDX-License: GPLv2 */
+/*
+ * This will zero-initialize local stack variables. (Though structure
+ * padding may remain uninitialized in certain cases.)
+ *
+ * Implements Florian Weimer's "-finit-local-vars" gcc patch as a plugin:
+ * https://gcc.gnu.org/ml/gcc-patches/2014-06/msg00615.html
+ *
+ * Plugin skeleton code thanks to PaX Team.
+ *
+ * Options:
+ * -fplugin-arg-stackinit_plugin-disable
+ */
+
+#include "gcc-common.h"
+
+__visible int plugin_is_GPL_compatible;
+
+static struct plugin_info stackinit_plugin_info = {
+	.version	= "20190122",
+	.help		= "disable\tdo not activate plugin\n",
+};
+
+static void finish_decl(void *event_data, void *data)
+{
+	tree decl = (tree)event_data;
+	tree type;
+
+	if (TREE_CODE (decl) != VAR_DECL)
+		return;
+
+	if (DECL_EXTERNAL (decl))
+		return;
+
+	if (DECL_INITIAL (decl) != NULL_TREE)
+		return;
+
+	if (global_bindings_p ())
+		return;
+
+	type = TREE_TYPE (decl);
+	if (AGGREGATE_TYPE_P (type))
+		DECL_INITIAL (decl) = build_constructor (type, NULL);
+	else
+		DECL_INITIAL (decl) = fold_convert (type, integer_zero_node);
+}
+
+__visible int plugin_init(struct plugin_name_args *plugin_info, struct plugin_gcc_version *version)
+{
+	int i;
+	const char * const plugin_name = plugin_info->base_name;
+	const int argc = plugin_info->argc;
+	const struct plugin_argument * const argv = plugin_info->argv;
+	bool enable = true;
+
+	if (!plugin_default_version_check(version, &gcc_version)) {
+		error(G_("incompatible gcc/plugin versions"));
+		return 1;
+	}
+
+	if (strncmp(lang_hooks.name, "GNU C", 5) && !strncmp(lang_hooks.name, "GNU C+", 6)) {
+		inform(UNKNOWN_LOCATION, G_("%s supports C only, not %s"), plugin_name, lang_hooks.name);
+		enable = false;
+	}
+
+	for (i = 0; i < argc; ++i) {
+		if (!strcmp(argv[i].key, "disable")) {
+			enable = false;
+			continue;
+		}
+		error(G_("unknown option '-fplugin-arg-%s-%s'"), plugin_name, argv[i].key);
+	}
+
+	register_callback(plugin_name, PLUGIN_INFO, NULL, &stackinit_plugin_info);
+	if (enable)
+		register_callback(plugin_name, PLUGIN_FINISH_DECL, finish_decl, NULL);
+
+	return 0;
+}
-- 
2.17.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* [PATCH 3/3] lib: Introduce test_stackinit module
  2019-01-23 11:03 [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Kees Cook
  2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
  2019-01-23 11:03 ` [PATCH 2/3] gcc-plugins: Introduce stackinit plugin Kees Cook
@ 2019-01-23 11:03 ` Kees Cook
  2019-01-29  0:12 ` [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Alexander Popov
  3 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2019-01-23 11:03 UTC (permalink / raw)
  To: linux-kernel
  Cc: Kees Cook, Ard Biesheuvel, Laura Abbott, Alexander Popov,
	xen-devel, dri-devel, intel-gfx, intel-wired-lan, netdev,
	linux-usb, linux-fsdevel, linux-mm, dev, linux-kbuild,
	linux-security-module, kernel-hardening

Adds test for stack initialization coverage. We have several build options
that control the level of stack variable initialization. This test lets us
visualize which options cover which cases, and provide tests for options
that are currently not available (padding initialization).

All options pass the explicit initialization cases and the partial
initializers (even with padding):

test_stackinit: u8_zero ok
test_stackinit: u16_zero ok
test_stackinit: u32_zero ok
test_stackinit: u64_zero ok
test_stackinit: char_array_zero ok
test_stackinit: small_hole_zero ok
test_stackinit: big_hole_zero ok
test_stackinit: packed_zero ok
test_stackinit: small_hole_dynamic_partial ok
test_stackinit: big_hole_dynamic_partial ok
test_stackinit: packed_static_partial ok
test_stackinit: small_hole_static_partial ok
test_stackinit: big_hole_static_partial ok

The results of the other tests (which contain no explicit initialization),
change based on the build's configured compiler instrumentation.

No options:

test_stackinit: small_hole_static_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_static_all FAIL (uninit bytes: 61)
test_stackinit: small_hole_dynamic_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_dynamic_all FAIL (uninit bytes: 61)
test_stackinit: small_hole_runtime_partial FAIL (uninit bytes: 23)
test_stackinit: big_hole_runtime_partial FAIL (uninit bytes: 127)
test_stackinit: small_hole_runtime_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_runtime_all FAIL (uninit bytes: 61)
test_stackinit: u8 FAIL (uninit bytes: 1)
test_stackinit: u16 FAIL (uninit bytes: 2)
test_stackinit: u32 FAIL (uninit bytes: 4)
test_stackinit: u64 FAIL (uninit bytes: 8)
test_stackinit: char_array FAIL (uninit bytes: 16)
test_stackinit: small_hole FAIL (uninit bytes: 24)
test_stackinit: big_hole FAIL (uninit bytes: 128)
test_stackinit: user FAIL (uninit bytes: 32)
test_stackinit: failures: 16

CONFIG_GCC_PLUGIN_STRUCTLEAK=y
This only tries to initialize structs with __user markings:

test_stackinit: small_hole_static_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_static_all FAIL (uninit bytes: 61)
test_stackinit: small_hole_dynamic_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_dynamic_all FAIL (uninit bytes: 61)
test_stackinit: small_hole_runtime_partial FAIL (uninit bytes: 23)
test_stackinit: big_hole_runtime_partial FAIL (uninit bytes: 127)
test_stackinit: small_hole_runtime_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_runtime_all FAIL (uninit bytes: 61)
test_stackinit: u8 FAIL (uninit bytes: 1)
test_stackinit: u16 FAIL (uninit bytes: 2)
test_stackinit: u32 FAIL (uninit bytes: 4)
test_stackinit: u64 FAIL (uninit bytes: 8)
test_stackinit: char_array FAIL (uninit bytes: 16)
test_stackinit: small_hole FAIL (uninit bytes: 24)
test_stackinit: big_hole FAIL (uninit bytes: 128)
test_stackinit: user ok
test_stackinit: failures: 15

CONFIG_GCC_PLUGIN_STRUCTLEAK=y
CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL=y
This initializes all structures passed by reference (scalars and strings
remain uninitialized, but padding is wiped):

test_stackinit: small_hole_static_all ok
test_stackinit: big_hole_static_all ok
test_stackinit: small_hole_dynamic_all ok
test_stackinit: big_hole_dynamic_all ok
test_stackinit: small_hole_runtime_partial ok
test_stackinit: big_hole_runtime_partial ok
test_stackinit: small_hole_runtime_all ok
test_stackinit: big_hole_runtime_all ok
test_stackinit: u8 FAIL (uninit bytes: 1)
test_stackinit: u16 FAIL (uninit bytes: 2)
test_stackinit: u32 FAIL (uninit bytes: 4)
test_stackinit: u64 FAIL (uninit bytes: 8)
test_stackinit: char_array FAIL (uninit bytes: 16)
test_stackinit: small_hole ok
test_stackinit: big_hole ok
test_stackinit: user ok
test_stackinit: failures: 5

CONFIG_GCC_PLUGIN_STACKINIT=y
This initializes all variables, but has no special padding handling:

test_stackinit: small_hole_static_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_static_all FAIL (uninit bytes: 61)
test_stackinit: small_hole_dynamic_all FAIL (uninit bytes: 3)
test_stackinit: big_hole_dynamic_all FAIL (uninit bytes: 61)
test_stackinit: small_hole_runtime_partial ok
test_stackinit: big_hole_runtime_partial ok
test_stackinit: small_hole_runtime_all ok
test_stackinit: big_hole_runtime_all ok
test_stackinit: u8 ok
test_stackinit: u16 ok
test_stackinit: u32 ok
test_stackinit: u64 ok
test_stackinit: char_array ok
test_stackinit: small_hole ok
test_stackinit: big_hole ok
test_stackinit: user ok
test_stackinit: failures: 4

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 lib/Kconfig.debug    |   9 ++
 lib/Makefile         |   1 +
 lib/test_stackinit.c | 327 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 337 insertions(+)
 create mode 100644 lib/test_stackinit.c

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d4df5b24d75e..09788afcccc9 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -2001,6 +2001,15 @@ config TEST_OBJAGG
 
 	  If unsure, say N.
 
+config TEST_STACKINIT
+	tristate "Test level of stack variable initialization"
+	help
+	  Test if the kernel is zero-initializing stack variables
+	  from CONFIG_GCC_PLUGIN_STACKINIT, CONFIG_GCC_PLUGIN_STRUCTLEAK,
+	  and/or GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
+
+	  If unsure, say N.
+
 endif # RUNTIME_TESTING_MENU
 
 config MEMTEST
diff --git a/lib/Makefile b/lib/Makefile
index e1b59da71418..c81a66d4d00d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -76,6 +76,7 @@ obj-$(CONFIG_TEST_KMOD) += test_kmod.o
 obj-$(CONFIG_TEST_DEBUG_VIRTUAL) += test_debug_virtual.o
 obj-$(CONFIG_TEST_MEMCAT_P) += test_memcat_p.o
 obj-$(CONFIG_TEST_OBJAGG) += test_objagg.o
+obj-$(CONFIG_TEST_STACKINIT) += test_stackinit.o
 
 ifeq ($(CONFIG_DEBUG_KOBJECT),y)
 CFLAGS_kobject.o += -DDEBUG
diff --git a/lib/test_stackinit.c b/lib/test_stackinit.c
new file mode 100644
index 000000000000..e2ff56a1002a
--- /dev/null
+++ b/lib/test_stackinit.c
@@ -0,0 +1,327 @@
+// SPDX-Licenses: GPLv2
+/*
+ * Test cases for -finit-local-vars and CONFIG_GCC_PLUGIN_STACKINIT.
+ */
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/string.h>
+
+/* Exfiltration buffer. */
+#define MAX_VAR_SIZE	128
+static char check_buf[MAX_VAR_SIZE];
+
+/* Character array to trigger stack protector in all functions. */
+#define VAR_BUFFER	 32
+
+/* Volatile mask to convince compiler to copy memory with 0xff. */
+static volatile u8 forced_mask = 0xff;
+
+/* Location and size tracking to validate fill and test are colocated. */
+static void *fill_start, *target_start;
+static size_t fill_size, target_size;
+
+static bool range_contains(char *haystack_start, size_t haystack_size,
+			   char *needle_start, size_t needle_size)
+{
+	if (needle_start >= haystack_start &&
+	    needle_start + needle_size <= haystack_start + haystack_size)
+		return true;
+	return false;
+}
+
+#define DO_NOTHING_TYPE_SCALAR(var_type)	var_type
+#define DO_NOTHING_TYPE_STRING(var_type)	void
+#define DO_NOTHING_TYPE_STRUCT(var_type)	void
+
+#define DO_NOTHING_RETURN_SCALAR(ptr)		*(ptr)
+#define DO_NOTHING_RETURN_STRING(ptr)		/**/
+#define DO_NOTHING_RETURN_STRUCT(ptr)		/**/
+
+#define DO_NOTHING_CALL_SCALAR(var, name)			\
+		(var) = do_nothing_ ## name(&(var))
+#define DO_NOTHING_CALL_STRING(var, name)			\
+		do_nothing_ ## name(var)
+#define DO_NOTHING_CALL_STRUCT(var, name)			\
+		do_nothing_ ## name(&(var))
+
+#define FETCH_ARG_SCALAR(var)		&var
+#define FETCH_ARG_STRING(var)		var
+#define FETCH_ARG_STRUCT(var)		&var
+
+#define FILL_SIZE_SCALAR		1
+#define FILL_SIZE_STRING		16
+#define FILL_SIZE_STRUCT		1
+
+#define INIT_CLONE_SCALAR		/**/
+#define INIT_CLONE_STRING		[FILL_SIZE_STRING]
+#define INIT_CLONE_STRUCT		/**/
+
+#define INIT_SCALAR_NONE		/**/
+#define INIT_SCALAR_ZERO		= 0
+
+#define INIT_STRING_NONE		[FILL_SIZE_STRING] /**/
+#define INIT_STRING_ZERO		[FILL_SIZE_STRING] = { }
+
+#define INIT_STRUCT_NONE		/**/
+#define INIT_STRUCT_ZERO		= { }
+#define INIT_STRUCT_STATIC_PARTIAL	= { .two = 0, }
+#define INIT_STRUCT_STATIC_ALL		= { .one = arg->one,		\
+					    .two = arg->two,		\
+					    .three = arg->three,	\
+					    .four = arg->four,		\
+					}
+#define INIT_STRUCT_DYNAMIC_PARTIAL	= { .two = arg->two, }
+#define INIT_STRUCT_DYNAMIC_ALL		= { .one = arg->one,		\
+					    .two = arg->two,		\
+					    .three = arg->three,	\
+					    .four = arg->four,		\
+					}
+#define INIT_STRUCT_RUNTIME_PARTIAL	;				\
+					var.two = 0
+#define INIT_STRUCT_RUNTIME_ALL		;				\
+					var.one = 0;			\
+					var.two = 0;			\
+					var.three = 0;			\
+					memset(&var.four, 0,		\
+					       sizeof(var.four))
+
+/*
+ * @name: unique string name for the test
+ * @var_type: type to be tested for zeroing initialization
+ * @which: is this a SCALAR or a STRUCT type?
+ * @init_level: what kind of initialization is performed
+ */
+#define DEFINE_TEST(name, var_type, which, init_level)		\
+static noinline int fill_ ## name(unsigned long sp)		\
+{								\
+	char buf[VAR_BUFFER +					\
+		 sizeof(var_type) * FILL_SIZE_ ## which * 4];	\
+								\
+	fill_start = buf;					\
+	fill_size = sizeof(buf);				\
+	/* Fill variable with 0xFF. */				\
+	memset(fill_start, (char)((sp && 0xff) | forced_mask),	\
+	       fill_size);					\
+								\
+	return (int)buf[0] | (int)buf[sizeof(buf)-1];		\
+}								\
+/* no-op to force compiler into ignoring "uninitialized" vars */\
+static noinline DO_NOTHING_TYPE_ ## which(var_type)		\
+do_nothing_ ## name(var_type *ptr)				\
+{								\
+	/* Will always be true, but compiler doesn't know. */	\
+	if ((unsigned long)ptr > 0x2)				\
+		return DO_NOTHING_RETURN_ ## which(ptr);	\
+	else							\
+		return DO_NOTHING_RETURN_ ## which(ptr + 1);	\
+}								\
+static noinline int fetch_ ## name(unsigned long sp,		\
+				   var_type *arg)		\
+{								\
+	char buf[VAR_BUFFER];					\
+	var_type var INIT_ ## which ## _ ## init_level;		\
+								\
+	target_start = &var;					\
+	target_size = sizeof(var);				\
+	/*							\
+	 * Keep this buffer around to make sure we've got a	\
+	 * stack frame of SOME kind...				\
+	 */							\
+	memset(buf, (char)(sp && 0xff), sizeof(buf));		\
+								\
+	/* Silence "never initialized" warnings. */		\
+	DO_NOTHING_CALL_ ## which(var, name);			\
+								\
+	/* Exfiltrate "var" or field of "var". */		\
+	memcpy(check_buf, target_start, target_size);		\
+								\
+	return (int)buf[0] | (int)buf[sizeof(buf) - 1];		\
+}								\
+/* Returns 0 on success, 1 on failure. */			\
+static noinline int test_ ## name (void)			\
+{								\
+	var_type zero INIT_CLONE_ ## which;			\
+	int ignored;						\
+	u8 sum = 0, i;						\
+								\
+	/* Notice when a new test is larger than expected. */	\
+	BUILD_BUG_ON(sizeof(zero) > MAX_VAR_SIZE);		\
+	/* Clear entire check buffer for later bit tests. */	\
+	memset(check_buf, 0x00, sizeof(check_buf));		\
+								\
+	/* Fill clone type with zero for per-field init. */	\
+	memset(&zero, 0x00, sizeof(zero));			\
+	/* Fill stack with 0xFF. */				\
+	ignored = fill_ ##name((unsigned long)&ignored);	\
+	/* Extract stack-defined variable contents. */		\
+	ignored = fetch_ ##name((unsigned long)&ignored,	\
+				FETCH_ARG_ ## which(zero));	\
+								\
+	/* Validate that compiler lined up fill and target. */	\
+	if (!range_contains(fill_start, fill_size,		\
+			    target_start, target_size)) {	\
+		pr_err(#name ": stack fill missed target!?\n");	\
+		pr_err(#name ": fill %zu wide\n", fill_size);	\
+		pr_err(#name ": target offset by %ld\n",	\
+			(ssize_t)(uintptr_t)fill_start -	\
+			(ssize_t)(uintptr_t)target_start);	\
+		return 1;					\
+	}							\
+								\
+	/* Look for any set bits in the check region. */	\
+	for (i = 0; i < sizeof(check_buf); i++)			\
+		sum += (check_buf[i] != 0);			\
+								\
+	if (sum == 0)						\
+		pr_info(#name " ok\n");				\
+	else							\
+		pr_warn(#name " FAIL (uninit bytes: %d)\n",	\
+			sum);					\
+								\
+	return (sum != 0);					\
+}
+
+/* Structure with no padding. */
+struct test_packed {
+	unsigned long one;
+	unsigned long two;
+	unsigned long three;
+	unsigned long four;
+};
+
+/* Simple structure with padding likely to be covered by compiler. */
+struct test_small_hole {
+	size_t one;
+	char two;
+	/* 3 byte padding hole here. */
+	int three;
+	unsigned long four;
+};
+
+/* Try to trigger unhandled padding in a structure. */
+struct test_aligned {
+	u32 internal1;
+	u64 internal2;
+} __aligned(64);
+
+struct test_big_hole {
+	u8 one;
+	u8 two;
+	u8 three;
+	/* 61 byte padding hole here. */
+	struct test_aligned four;
+} __aligned(64);
+
+/* Test if STRUCTLEAK is clearing structs with __user fields. */
+struct test_user {
+	u8 one;
+	char __user *two;
+	unsigned long three;
+	unsigned long four;
+};
+
+/* These should be fully initialized all the time! */
+DEFINE_TEST(u8_zero, u8, SCALAR, ZERO);
+DEFINE_TEST(u16_zero, u16, SCALAR, ZERO);
+DEFINE_TEST(u32_zero, u32, SCALAR, ZERO);
+DEFINE_TEST(u64_zero, u64, SCALAR, ZERO);
+DEFINE_TEST(char_array_zero, unsigned char, STRING, ZERO);
+
+DEFINE_TEST(packed_zero, struct test_packed, STRUCT, ZERO);
+DEFINE_TEST(small_hole_zero, struct test_small_hole, STRUCT, ZERO);
+DEFINE_TEST(big_hole_zero, struct test_big_hole, STRUCT, ZERO);
+
+/* Static initialization: padding may be left uninitialized. */
+DEFINE_TEST(packed_static_partial, struct test_packed, STRUCT, STATIC_PARTIAL);
+DEFINE_TEST(small_hole_static_partial, struct test_small_hole, STRUCT, STATIC_PARTIAL);
+DEFINE_TEST(big_hole_static_partial, struct test_big_hole, STRUCT, STATIC_PARTIAL);
+
+DEFINE_TEST(small_hole_static_all, struct test_small_hole, STRUCT, STATIC_ALL);
+DEFINE_TEST(big_hole_static_all, struct test_big_hole, STRUCT, STATIC_ALL);
+
+/* Dynamic initialization: padding may be left uninitialized. */
+DEFINE_TEST(small_hole_dynamic_partial, struct test_small_hole, STRUCT, DYNAMIC_PARTIAL);
+DEFINE_TEST(big_hole_dynamic_partial, struct test_big_hole, STRUCT, DYNAMIC_PARTIAL);
+
+DEFINE_TEST(small_hole_dynamic_all, struct test_small_hole, STRUCT, DYNAMIC_ALL);
+DEFINE_TEST(big_hole_dynamic_all, struct test_big_hole, STRUCT, DYNAMIC_ALL);
+
+/* Runtime initialization: padding may be left uninitialized. */
+DEFINE_TEST(small_hole_runtime_partial, struct test_small_hole, STRUCT, RUNTIME_PARTIAL);
+DEFINE_TEST(big_hole_runtime_partial, struct test_big_hole, STRUCT, RUNTIME_PARTIAL);
+
+DEFINE_TEST(small_hole_runtime_all, struct test_small_hole, STRUCT, RUNTIME_ALL);
+DEFINE_TEST(big_hole_runtime_all, struct test_big_hole, STRUCT, RUNTIME_ALL);
+
+/* No initialization without compiler instrumentation. */
+DEFINE_TEST(u8, u8, SCALAR, NONE);
+DEFINE_TEST(u16, u16, SCALAR, NONE);
+DEFINE_TEST(u32, u32, SCALAR, NONE);
+DEFINE_TEST(u64, u64, SCALAR, NONE);
+DEFINE_TEST(char_array, unsigned char, STRING, NONE);
+DEFINE_TEST(small_hole, struct test_small_hole, STRUCT, NONE);
+DEFINE_TEST(big_hole, struct test_big_hole, STRUCT, NONE);
+DEFINE_TEST(user, struct test_user, STRUCT, NONE);
+
+static int __init test_stackinit_init(void)
+{
+	unsigned int failures = 0;
+
+	/* These are explicitly initialized and should always pass. */
+	failures += test_u8_zero();
+	failures += test_u16_zero();
+	failures += test_u32_zero();
+	failures += test_u64_zero();
+	failures += test_char_array_zero();
+	failures += test_small_hole_zero();
+	failures += test_big_hole_zero();
+	failures += test_packed_zero();
+
+	/* Padding here appears to be accidentally always initialized. */
+	failures += test_small_hole_dynamic_partial();
+	failures += test_big_hole_dynamic_partial();
+	failures += test_packed_static_partial();
+
+	/* Padding initialization depends on compiler behaviors. */
+	failures += test_small_hole_static_partial();
+	failures += test_big_hole_static_partial();
+	failures += test_small_hole_static_all();
+	failures += test_big_hole_static_all();
+	failures += test_small_hole_dynamic_all();
+	failures += test_big_hole_dynamic_all();
+	failures += test_small_hole_runtime_partial();
+	failures += test_big_hole_runtime_partial();
+	failures += test_small_hole_runtime_all();
+	failures += test_big_hole_runtime_all();
+
+	/* STACKINIT should cover everything from here down. */
+	failures += test_u8();
+	failures += test_u16();
+	failures += test_u32();
+	failures += test_u64();
+	failures += test_char_array();
+
+	/* STRUCTLEAK_BYREF_ALL should cover from here down. */
+	failures += test_small_hole();
+	failures += test_big_hole();
+
+	/* STRUCTLEAK should cover this. */
+	failures += test_user();
+
+	if (failures == 0)
+		pr_info("all tests passed!\n");
+	else
+		pr_err("failures: %u\n", failures);
+
+	return failures ? -EINVAL : 0;
+}
+module_init(test_stackinit_init);
+
+static void __exit test_stackinit_exit(void)
+{ }
+module_exit(test_stackinit_exit);
+
+MODULE_LICENSE("GPL");
-- 
2.17.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
@ 2019-01-23 11:58   ` Greg KH
  2019-01-23 12:09     ` Jann Horn
  2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
  2019-01-23 16:51   ` [Intel-wired-lan] " Jeff Kirsher
  2019-01-24 12:58   ` Edwin Zimmerman
  2 siblings, 2 replies; 20+ messages in thread
From: Greg KH @ 2019-01-23 11:58 UTC (permalink / raw)
  To: Kees Cook
  Cc: linux-kernel, Ard Biesheuvel, Laura Abbott, Alexander Popov,
	xen-devel, dri-devel, intel-gfx, intel-wired-lan, netdev,
	linux-usb, linux-fsdevel, linux-mm, dev, linux-kbuild,
	linux-security-module, kernel-hardening

On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> Variables declared in a switch statement before any case statements
> cannot be initialized, so move all instances out of the switches.
> After this, future always-initialized stack variables will work
> and not throw warnings like this:
> 
> fs/fcntl.c: In function ‘send_sigio_to_task’:
> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
>    siginfo_t si;
>              ^~

That's a pain, so this means we can't have any new variables in { }
scope except for at the top of a function?

That's going to be a hard thing to keep from happening over time, as
this is valid C :(

greg k-h

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 11:58   ` Greg KH
@ 2019-01-23 12:09     ` Jann Horn
  2019-01-23 12:12       ` Ard Biesheuvel
  2019-01-23 13:21       ` William Kucharski
  2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
  1 sibling, 2 replies; 20+ messages in thread
From: Jann Horn @ 2019-01-23 12:09 UTC (permalink / raw)
  To: Greg KH
  Cc: Kees Cook, kernel list, Ard Biesheuvel, Laura Abbott,
	Alexander Popov, xen-devel, dri-devel, intel-gfx,
	intel-wired-lan, Network Development, linux-usb, linux-fsdevel,
	Linux-MM, dev, linux-kbuild, linux-security-module,
	Kernel Hardening

On Wed, Jan 23, 2019 at 1:04 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> > Variables declared in a switch statement before any case statements
> > cannot be initialized, so move all instances out of the switches.
> > After this, future always-initialized stack variables will work
> > and not throw warnings like this:
> >
> > fs/fcntl.c: In function ‘send_sigio_to_task’:
> > fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
> >    siginfo_t si;
> >              ^~
>
> That's a pain, so this means we can't have any new variables in { }
> scope except for at the top of a function?

AFAICS this only applies to switch statements (because they jump to a
case and don't execute stuff at the start of the block), not blocks
after if/while/... .

> That's going to be a hard thing to keep from happening over time, as
> this is valid C :(

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 12:09     ` Jann Horn
@ 2019-01-23 12:12       ` Ard Biesheuvel
  2019-01-23 13:21       ` William Kucharski
  1 sibling, 0 replies; 20+ messages in thread
From: Ard Biesheuvel @ 2019-01-23 12:12 UTC (permalink / raw)
  To: Jann Horn
  Cc: Greg KH, Kees Cook, kernel list, Laura Abbott, Alexander Popov,
	xen-devel, dri-devel, intel-gfx, intel-wired-lan,
	Network Development, linux-usb, linux-fsdevel, Linux-MM, dev,
	Linux Kbuild mailing list, linux-security-module,
	Kernel Hardening

On Wed, 23 Jan 2019 at 13:09, Jann Horn <jannh@google.com> wrote:
>
> On Wed, Jan 23, 2019 at 1:04 PM Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> > > Variables declared in a switch statement before any case statements
> > > cannot be initialized, so move all instances out of the switches.
> > > After this, future always-initialized stack variables will work
> > > and not throw warnings like this:
> > >
> > > fs/fcntl.c: In function ‘send_sigio_to_task’:
> > > fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
> > >    siginfo_t si;
> > >              ^~
> >
> > That's a pain, so this means we can't have any new variables in { }
> > scope except for at the top of a function?
>
> AFAICS this only applies to switch statements (because they jump to a
> case and don't execute stuff at the start of the block), not blocks
> after if/while/... .
>

I guess that means it may apply to other cases where you do a 'goto'
into the middle of a for() loop, for instance (at the first
iteration), which is also a valid pattern.

Is there any way to tag these assignments so the diagnostic disregards them?

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 12:09     ` Jann Horn
  2019-01-23 12:12       ` Ard Biesheuvel
@ 2019-01-23 13:21       ` William Kucharski
  1 sibling, 0 replies; 20+ messages in thread
From: William Kucharski @ 2019-01-23 13:21 UTC (permalink / raw)
  To: Jann Horn
  Cc: Greg KH, Kees Cook, kernel list, Ard Biesheuvel, Laura Abbott,
	Alexander Popov, xen-devel, dri-devel, intel-gfx,
	intel-wired-lan, Network Development, linux-usb, linux-fsdevel,
	Linux-MM, dev, linux-kbuild, linux-security-module,
	Kernel Hardening



> On Jan 23, 2019, at 5:09 AM, Jann Horn <jannh@google.com> wrote:
> 
> AFAICS this only applies to switch statements (because they jump to a
> case and don't execute stuff at the start of the block), not blocks
> after if/while/... .

It bothers me that we are going out of our way to deprecate valid C constructs
in favor of placing the declarations elsewhere.

As current compiler warnings would catch any reference before initialization
usage anyway, it seems like we are letting a compiler warning rather than the
language standard dictate syntax.

Certainly if we want to make it a best practice coding style issue we can, and
then an appropriate note explaining why should be added to
Documentation/process/coding-style.rst.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 11:58   ` Greg KH
  2019-01-23 12:09     ` Jann Horn
@ 2019-01-23 14:17     ` Jani Nikula
  2019-01-23 14:23       ` Jani Nikula
                         ` (2 more replies)
  1 sibling, 3 replies; 20+ messages in thread
From: Jani Nikula @ 2019-01-23 14:17 UTC (permalink / raw)
  To: Greg KH, Kees Cook
  Cc: dev, Ard Biesheuvel, netdev, intel-gfx, linux-usb, linux-kernel,
	dri-devel, linux-mm, linux-security-module, kernel-hardening,
	intel-wired-lan, linux-fsdevel, xen-devel, Laura Abbott,
	linux-kbuild, Alexander Popov

On Wed, 23 Jan 2019, Greg KH <gregkh@linuxfoundation.org> wrote:
> On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
>> Variables declared in a switch statement before any case statements
>> cannot be initialized, so move all instances out of the switches.
>> After this, future always-initialized stack variables will work
>> and not throw warnings like this:
>> 
>> fs/fcntl.c: In function ‘send_sigio_to_task’:
>> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
>>    siginfo_t si;
>>              ^~
>
> That's a pain, so this means we can't have any new variables in { }
> scope except for at the top of a function?
>
> That's going to be a hard thing to keep from happening over time, as
> this is valid C :(

Not all valid C is meant to be used! ;)

Anyway, I think you're mistaking the limitation to arbitrary blocks
while it's only about the switch block IIUC.

Can't have:

	switch (i) {
		int j;
	case 0:
        	/* ... */
	}

because it can't be turned into:

	switch (i) {
		int j = 0; /* not valid C */
	case 0:
        	/* ... */
	}

but can have e.g.:

	switch (i) {
	case 0:
		{
			int j = 0;
	        	/* ... */
		}
	}

I think Kees' approach of moving such variable declarations to the
enclosing block scope is better than adding another nesting block.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
@ 2019-01-23 14:23       ` Jani Nikula
  2019-01-23 14:47       ` Edwin Zimmerman
  2019-01-23 19:18       ` Matthew Wilcox
  2 siblings, 0 replies; 20+ messages in thread
From: Jani Nikula @ 2019-01-23 14:23 UTC (permalink / raw)
  To: Greg KH, Kees Cook
  Cc: dev, Ard Biesheuvel, netdev, intel-gfx, linux-usb, linux-kernel,
	dri-devel, linux-mm, linux-security-module, kernel-hardening,
	intel-wired-lan, linux-fsdevel, xen-devel, Laura Abbott,
	linux-kbuild, Alexander Popov

On Wed, 23 Jan 2019, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Wed, 23 Jan 2019, Greg KH <gregkh@linuxfoundation.org> wrote:
>> On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
>>> Variables declared in a switch statement before any case statements
>>> cannot be initialized, so move all instances out of the switches.
>>> After this, future always-initialized stack variables will work
>>> and not throw warnings like this:
>>> 
>>> fs/fcntl.c: In function ‘send_sigio_to_task’:
>>> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
>>>    siginfo_t si;
>>>              ^~
>>
>> That's a pain, so this means we can't have any new variables in { }
>> scope except for at the top of a function?
>>
>> That's going to be a hard thing to keep from happening over time, as
>> this is valid C :(
>
> Not all valid C is meant to be used! ;)
>
> Anyway, I think you're mistaking the limitation to arbitrary blocks
> while it's only about the switch block IIUC.
>
> Can't have:
>
> 	switch (i) {
> 		int j;
> 	case 0:
>         	/* ... */
> 	}
>
> because it can't be turned into:
>
> 	switch (i) {
> 		int j = 0; /* not valid C */
> 	case 0:
>         	/* ... */
> 	}
>
> but can have e.g.:
>
> 	switch (i) {
> 	case 0:
> 		{
> 			int j = 0;
> 	        	/* ... */
> 		}
> 	}
>
> I think Kees' approach of moving such variable declarations to the
> enclosing block scope is better than adding another nesting block.

PS. The patch is

Reviewed-by: Jani Nikula <jani.nikula@intel.com>

and the drivers/gpu/drm/i915/* parts are

Acked-by: Jani Nikula <jani.nikula@intel.com>

for merging via whichever tree is appropriate. (There'll be minor
conflicts with in-flight work in our -next tree, but no biggie.)


-- 
Jani Nikula, Intel Open Source Graphics Center

^ permalink raw reply	[flat|nested] 20+ messages in thread

* RE: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
  2019-01-23 14:23       ` Jani Nikula
@ 2019-01-23 14:47       ` Edwin Zimmerman
  2019-01-23 15:46         ` Jani Nikula
  2019-01-23 19:18       ` Matthew Wilcox
  2 siblings, 1 reply; 20+ messages in thread
From: Edwin Zimmerman @ 2019-01-23 14:47 UTC (permalink / raw)
  To: 'Jani Nikula', 'Greg KH', 'Kees Cook'
  Cc: dev, 'Ard Biesheuvel',
	netdev, intel-gfx, linux-usb, linux-kernel, dri-devel, linux-mm,
	linux-security-module, kernel-hardening, intel-wired-lan,
	linux-fsdevel, xen-devel, 'Laura Abbott',
	linux-kbuild, 'Alexander Popov'

On Wed, 23 Jan 2019, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Wed, 23 Jan 2019, Greg KH <gregkh@linuxfoundation.org> wrote:
> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> >> Variables declared in a switch statement before any case statements
> >> cannot be initialized, so move all instances out of the switches.
> >> After this, future always-initialized stack variables will work
> >> and not throw warnings like this:
> >>
> >> fs/fcntl.c: In function ‘send_sigio_to_task’:
> >> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
> >>    siginfo_t si;
> >>              ^~
> >
> > That's a pain, so this means we can't have any new variables in { }
> > scope except for at the top of a function?
> >
> > That's going to be a hard thing to keep from happening over time, as
> > this is valid C :(
> 
> Not all valid C is meant to be used! ;)

Very true.  The other thing to keep in mind is the burden of enforcing a prohibition on a valid C construct like this.  
It seems to me that patch reviewers and maintainers have enough to do without forcing them to watch for variable
declarations in switch statements.  Automating this prohibition, should it be accepted, seems like a good idea to me.

-Edwin Zimmerman


^ permalink raw reply	[flat|nested] 20+ messages in thread

* RE: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 14:47       ` Edwin Zimmerman
@ 2019-01-23 15:46         ` Jani Nikula
  2019-01-23 18:55           ` Kees Cook
  0 siblings, 1 reply; 20+ messages in thread
From: Jani Nikula @ 2019-01-23 15:46 UTC (permalink / raw)
  To: Edwin Zimmerman, 'Greg KH', 'Kees Cook'
  Cc: dev, 'Ard Biesheuvel',
	netdev, intel-gfx, linux-usb, linux-kernel, dri-devel, linux-mm,
	linux-security-module, kernel-hardening, intel-wired-lan,
	linux-fsdevel, xen-devel, 'Laura Abbott',
	linux-kbuild, 'Alexander Popov'

On Wed, 23 Jan 2019, Edwin Zimmerman <edwin@211mainstreet.net> wrote:
> On Wed, 23 Jan 2019, Jani Nikula <jani.nikula@linux.intel.com> wrote:
>> On Wed, 23 Jan 2019, Greg KH <gregkh@linuxfoundation.org> wrote:
>> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
>> >> Variables declared in a switch statement before any case statements
>> >> cannot be initialized, so move all instances out of the switches.
>> >> After this, future always-initialized stack variables will work
>> >> and not throw warnings like this:
>> >>
>> >> fs/fcntl.c: In function ‘send_sigio_to_task’:
>> >> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
>> >>    siginfo_t si;
>> >>              ^~
>> >
>> > That's a pain, so this means we can't have any new variables in { }
>> > scope except for at the top of a function?
>> >
>> > That's going to be a hard thing to keep from happening over time, as
>> > this is valid C :(
>> 
>> Not all valid C is meant to be used! ;)
>
> Very true.  The other thing to keep in mind is the burden of enforcing
> a prohibition on a valid C construct like this.  It seems to me that
> patch reviewers and maintainers have enough to do without forcing them
> to watch for variable declarations in switch statements.  Automating
> this prohibition, should it be accepted, seems like a good idea to me.

Considering that the treewide diffstat to fix this is:

 18 files changed, 45 insertions(+), 46 deletions(-)

and using the gcc plugin in question will trigger the switch-unreachable
warning, I think we're good. There'll probably be the occasional
declarations that pass through, and will get fixed afterwards.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Graphics Center

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-wired-lan] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
  2019-01-23 11:58   ` Greg KH
@ 2019-01-23 16:51   ` Jeff Kirsher
  2019-01-24 12:58   ` Edwin Zimmerman
  2 siblings, 0 replies; 20+ messages in thread
From: Jeff Kirsher @ 2019-01-23 16:51 UTC (permalink / raw)
  To: Kees Cook, linux-kernel
  Cc: dev, Ard Biesheuvel, netdev, intel-gfx, linux-usb, dri-devel,
	linux-mm, linux-security-module, kernel-hardening,
	intel-wired-lan, linux-fsdevel, xen-devel, Laura Abbott,
	linux-kbuild, Alexander Popov

[-- Attachment #1: Type: text/plain, Size: 1791 bytes --]

On Wed, 2019-01-23 at 03:03 -0800, Kees Cook wrote:
> Variables declared in a switch statement before any case statements
> cannot be initialized, so move all instances out of the switches.
> After this, future always-initialized stack variables will work
> and not throw warnings like this:
> 
> fs/fcntl.c: In function ‘send_sigio_to_task’:
> fs/fcntl.c:738:13: warning: statement will never be executed [-
> Wswitch-unreachable]
>    siginfo_t si;
>              ^~
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>

Acked-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

For the e1000 changes.

> ---
>  arch/x86/xen/enlighten_pv.c                   |  7 ++++---
>  drivers/char/pcmcia/cm4000_cs.c               |  2 +-
>  drivers/char/ppdev.c                          | 20 ++++++++---------
> --
>  drivers/gpu/drm/drm_edid.c                    |  4 ++--
>  drivers/gpu/drm/i915/intel_display.c          |  2 +-
>  drivers/gpu/drm/i915/intel_pm.c               |  4 ++--
>  drivers/net/ethernet/intel/e1000/e1000_main.c |  3 ++-
>  drivers/tty/n_tty.c                           |  3 +--
>  drivers/usb/gadget/udc/net2280.c              |  5 ++---
>  fs/fcntl.c                                    |  3 ++-
>  mm/shmem.c                                    |  5 +++--
>  net/core/skbuff.c                             |  4 ++--
>  net/ipv6/ip6_gre.c                            |  4 ++--
>  net/ipv6/ip6_tunnel.c                         |  4 ++--
>  net/openvswitch/flow_netlink.c                |  7 +++----
>  security/tomoyo/common.c                      |  3 ++-
>  security/tomoyo/condition.c                   |  7 ++++---
>  security/tomoyo/util.c                        |  4 ++--
>  18 files changed, 45 insertions(+), 46 deletions(-)


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^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 15:46         ` Jani Nikula
@ 2019-01-23 18:55           ` Kees Cook
  2019-01-24  8:10             ` Greg KH
  0 siblings, 1 reply; 20+ messages in thread
From: Kees Cook @ 2019-01-23 18:55 UTC (permalink / raw)
  To: Jani Nikula
  Cc: Edwin Zimmerman, Greg KH, dev, Ard Biesheuvel,
	Network Development, intel-gfx, linux-usb, LKML,
	Maling list - DRI developers, Linux-MM, linux-security-module,
	Kernel Hardening, intel-wired-lan, linux-fsdevel, xen-devel,
	Laura Abbott, linux-kbuild, Alexander Popov

On Thu, Jan 24, 2019 at 4:44 AM Jani Nikula <jani.nikula@linux.intel.com> wrote:
>
> On Wed, 23 Jan 2019, Edwin Zimmerman <edwin@211mainstreet.net> wrote:
> > On Wed, 23 Jan 2019, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> >> On Wed, 23 Jan 2019, Greg KH <gregkh@linuxfoundation.org> wrote:
> >> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> >> >> Variables declared in a switch statement before any case statements
> >> >> cannot be initialized, so move all instances out of the switches.
> >> >> After this, future always-initialized stack variables will work
> >> >> and not throw warnings like this:
> >> >>
> >> >> fs/fcntl.c: In function ‘send_sigio_to_task’:
> >> >> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
> >> >>    siginfo_t si;
> >> >>              ^~
> >> >
> >> > That's a pain, so this means we can't have any new variables in { }
> >> > scope except for at the top of a function?

Just in case this wasn't clear: no, it's just the switch statement
before the first "case". I cannot imagine how bad it would be if we
couldn't have block-scoped variables! Heh. :)

> >> >
> >> > That's going to be a hard thing to keep from happening over time, as
> >> > this is valid C :(
> >>
> >> Not all valid C is meant to be used! ;)
> >
> > Very true.  The other thing to keep in mind is the burden of enforcing
> > a prohibition on a valid C construct like this.  It seems to me that
> > patch reviewers and maintainers have enough to do without forcing them
> > to watch for variable declarations in switch statements.  Automating
> > this prohibition, should it be accepted, seems like a good idea to me.
>
> Considering that the treewide diffstat to fix this is:
>
>  18 files changed, 45 insertions(+), 46 deletions(-)
>
> and using the gcc plugin in question will trigger the switch-unreachable
> warning, I think we're good. There'll probably be the occasional
> declarations that pass through, and will get fixed afterwards.

Yeah, that was my thinking as well: it's a rare use, and we get a
warning when it comes up.

Thanks!

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
  2019-01-23 14:23       ` Jani Nikula
  2019-01-23 14:47       ` Edwin Zimmerman
@ 2019-01-23 19:18       ` Matthew Wilcox
  2019-01-23 20:36         ` Kees Cook
  2 siblings, 1 reply; 20+ messages in thread
From: Matthew Wilcox @ 2019-01-23 19:18 UTC (permalink / raw)
  To: Jani Nikula
  Cc: Greg KH, Kees Cook, dev, Ard Biesheuvel, netdev, intel-gfx,
	linux-usb, linux-kernel, dri-devel, linux-mm,
	linux-security-module, kernel-hardening, intel-wired-lan,
	linux-fsdevel, xen-devel, Laura Abbott, linux-kbuild,
	Alexander Popov

On Wed, Jan 23, 2019 at 04:17:30PM +0200, Jani Nikula wrote:
> Can't have:
> 
> 	switch (i) {
> 		int j;
> 	case 0:
>         	/* ... */
> 	}
> 
> because it can't be turned into:
> 
> 	switch (i) {
> 		int j = 0; /* not valid C */
> 	case 0:
>         	/* ... */
> 	}
> 
> but can have e.g.:
> 
> 	switch (i) {
> 	case 0:
> 		{
> 			int j = 0;
> 	        	/* ... */
> 		}
> 	}
> 
> I think Kees' approach of moving such variable declarations to the
> enclosing block scope is better than adding another nesting block.

Another nesting level would be bad, but I think this is OK:

	switch (i) {
	case 0: {
		int j = 0;
        	/* ... */
	}
	case 1: {
		void *p = q;
		/* ... */
	}
	}

I can imagine Kees' patch might have a bad effect on stack consumption,
unless GCC can be relied on to be smart enough to notice the
non-overlapping liveness of the vriables and use the same stack slots
for both.

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 19:18       ` Matthew Wilcox
@ 2019-01-23 20:36         ` Kees Cook
  0 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2019-01-23 20:36 UTC (permalink / raw)
  To: Matthew Wilcox
  Cc: Jani Nikula, Greg KH, dev, Ard Biesheuvel, Network Development,
	intel-gfx, linux-usb, LKML, Maling list - DRI developers,
	Linux-MM, linux-security-module, Kernel Hardening,
	intel-wired-lan, linux-fsdevel, xen-devel, Laura Abbott,
	linux-kbuild, Alexander Popov

On Thu, Jan 24, 2019 at 8:18 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Wed, Jan 23, 2019 at 04:17:30PM +0200, Jani Nikula wrote:
> > Can't have:
> >
> >       switch (i) {
> >               int j;
> >       case 0:
> >               /* ... */
> >       }
> >
> > because it can't be turned into:
> >
> >       switch (i) {
> >               int j = 0; /* not valid C */
> >       case 0:
> >               /* ... */
> >       }
> >
> > but can have e.g.:
> >
> >       switch (i) {
> >       case 0:
> >               {
> >                       int j = 0;
> >                       /* ... */
> >               }
> >       }
> >
> > I think Kees' approach of moving such variable declarations to the
> > enclosing block scope is better than adding another nesting block.
>
> Another nesting level would be bad, but I think this is OK:
>
>         switch (i) {
>         case 0: {
>                 int j = 0;
>                 /* ... */
>         }
>         case 1: {
>                 void *p = q;
>                 /* ... */
>         }
>         }
>
> I can imagine Kees' patch might have a bad effect on stack consumption,
> unless GCC can be relied on to be smart enough to notice the
> non-overlapping liveness of the vriables and use the same stack slots
> for both.

GCC is reasonable at this. The main issue, though, was most of these
places were using the variables in multiple case statements, so they
couldn't be limited to a single block (or they'd need to be manually
repeated in each block, which is even more ugly, IMO).

Whatever the consensus, I'm happy to tweak the patch.

Thanks!

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [Intel-gfx] [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 18:55           ` Kees Cook
@ 2019-01-24  8:10             ` Greg KH
  0 siblings, 0 replies; 20+ messages in thread
From: Greg KH @ 2019-01-24  8:10 UTC (permalink / raw)
  To: Kees Cook
  Cc: Jani Nikula, Edwin Zimmerman, dev, Ard Biesheuvel,
	Network Development, intel-gfx, linux-usb, LKML,
	Maling list - DRI developers, Linux-MM, linux-security-module,
	Kernel Hardening, intel-wired-lan, linux-fsdevel, xen-devel,
	Laura Abbott, linux-kbuild, Alexander Popov

On Thu, Jan 24, 2019 at 07:55:51AM +1300, Kees Cook wrote:
> On Thu, Jan 24, 2019 at 4:44 AM Jani Nikula <jani.nikula@linux.intel.com> wrote:
> >
> > On Wed, 23 Jan 2019, Edwin Zimmerman <edwin@211mainstreet.net> wrote:
> > > On Wed, 23 Jan 2019, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> > >> On Wed, 23 Jan 2019, Greg KH <gregkh@linuxfoundation.org> wrote:
> > >> > On Wed, Jan 23, 2019 at 03:03:47AM -0800, Kees Cook wrote:
> > >> >> Variables declared in a switch statement before any case statements
> > >> >> cannot be initialized, so move all instances out of the switches.
> > >> >> After this, future always-initialized stack variables will work
> > >> >> and not throw warnings like this:
> > >> >>
> > >> >> fs/fcntl.c: In function ‘send_sigio_to_task’:
> > >> >> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
> > >> >>    siginfo_t si;
> > >> >>              ^~
> > >> >
> > >> > That's a pain, so this means we can't have any new variables in { }
> > >> > scope except for at the top of a function?
> 
> Just in case this wasn't clear: no, it's just the switch statement
> before the first "case". I cannot imagine how bad it would be if we
> couldn't have block-scoped variables! Heh. :)

Sorry, it was not clear at first glance.  So no more objection from me
for this change.

greg k-h

^ permalink raw reply	[flat|nested] 20+ messages in thread

* RE: [PATCH 1/3] treewide: Lift switch variables out of switches
  2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
  2019-01-23 11:58   ` Greg KH
  2019-01-23 16:51   ` [Intel-wired-lan] " Jeff Kirsher
@ 2019-01-24 12:58   ` Edwin Zimmerman
  2 siblings, 0 replies; 20+ messages in thread
From: Edwin Zimmerman @ 2019-01-24 12:58 UTC (permalink / raw)
  To: 'Kees Cook', linux-kernel
  Cc: 'Ard Biesheuvel', 'Laura Abbott',
	'Alexander Popov',
	xen-devel, dri-devel, intel-gfx, intel-wired-lan, netdev,
	linux-usb, linux-fsdevel, linux-mm, dev, linux-kbuild,
	linux-security-module, kernel-hardening

On Wednesday, January 23, 2019 6:04 AM, Kees Cook wrote
> 
> Variables declared in a switch statement before any case statements
> cannot be initialized, so move all instances out of the switches.
> After this, future always-initialized stack variables will work
> and not throw warnings like this:
> 
> fs/fcntl.c: In function ‘send_sigio_to_task’:
> fs/fcntl.c:738:13: warning: statement will never be executed [-Wswitch-unreachable]
>    siginfo_t si;
>              ^~
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed by: Edwin Zimmerman <edwin@211mainstreet.net>

> ---
>  arch/x86/xen/enlighten_pv.c                   |  7 ++++---
>  drivers/char/pcmcia/cm4000_cs.c               |  2 +-
>  drivers/char/ppdev.c                          | 20 ++++++++-----------
>  drivers/gpu/drm/drm_edid.c                    |  4 ++--
>  drivers/gpu/drm/i915/intel_display.c          |  2 +-
>  drivers/gpu/drm/i915/intel_pm.c               |  4 ++--
>  drivers/net/ethernet/intel/e1000/e1000_main.c |  3 ++-
>  drivers/tty/n_tty.c                           |  3 +--
>  drivers/usb/gadget/udc/net2280.c              |  5 ++---
>  fs/fcntl.c                                    |  3 ++-
>  mm/shmem.c                                    |  5 +++--
>  net/core/skbuff.c                             |  4 ++--
>  net/ipv6/ip6_gre.c                            |  4 ++--
>  net/ipv6/ip6_tunnel.c                         |  4 ++--
>  net/openvswitch/flow_netlink.c                |  7 +++----
>  security/tomoyo/common.c                      |  3 ++-
>  security/tomoyo/condition.c                   |  7 ++++---
>  security/tomoyo/util.c                        |  4 ++--
>  18 files changed, 45 insertions(+), 46 deletions(-)
> 
> diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
> index c54a493e139a..a79d4b548a08 100644
> --- a/arch/x86/xen/enlighten_pv.c
> +++ b/arch/x86/xen/enlighten_pv.c
> @@ -907,14 +907,15 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
>  static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
>  {
>  	int ret;
> +#ifdef CONFIG_X86_64
> +	unsigned which;
> +	u64 base;
> +#endif
> 
>  	ret = 0;
> 
>  	switch (msr) {
>  #ifdef CONFIG_X86_64
> -		unsigned which;
> -		u64 base;
> -
>  	case MSR_FS_BASE:		which = SEGBASE_FS; goto set;
>  	case MSR_KERNEL_GS_BASE:	which = SEGBASE_GS_USER; goto set;
>  	case MSR_GS_BASE:		which = SEGBASE_GS_KERNEL; goto set;
> diff --git a/drivers/char/pcmcia/cm4000_cs.c b/drivers/char/pcmcia/cm4000_cs.c
> index 7a4eb86aedac..7211dc0e6f4f 100644
> --- a/drivers/char/pcmcia/cm4000_cs.c
> +++ b/drivers/char/pcmcia/cm4000_cs.c
> @@ -663,6 +663,7 @@ static void monitor_card(struct timer_list *t)
>  {
>  	struct cm4000_dev *dev = from_timer(dev, t, timer);
>  	unsigned int iobase = dev->p_dev->resource[0]->start;
> +	unsigned char flags0;
>  	unsigned short s;
>  	struct ptsreq ptsreq;
>  	int i, atrc;
> @@ -731,7 +732,6 @@ static void monitor_card(struct timer_list *t)
>  	}
> 
>  	switch (dev->mstate) {
> -		unsigned char flags0;
>  	case M_CARDOFF:
>  		DEBUGP(4, dev, "M_CARDOFF\n");
>  		flags0 = inb(REG_FLAGS0(iobase));
> diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
> index 1ae77b41050a..d77c97e4f996 100644
> --- a/drivers/char/ppdev.c
> +++ b/drivers/char/ppdev.c
> @@ -359,14 +359,19 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  	struct pp_struct *pp = file->private_data;
>  	struct parport *port;
>  	void __user *argp = (void __user *)arg;
> +	struct ieee1284_info *info;
> +	unsigned char reg;
> +	unsigned char mask;
> +	int mode;
> +	s32 time32[2];
> +	s64 time64[2];
> +	struct timespec64 ts;
> +	int ret;
> 
>  	/* First handle the cases that don't take arguments. */
>  	switch (cmd) {
>  	case PPCLAIM:
>  	    {
> -		struct ieee1284_info *info;
> -		int ret;
> -
>  		if (pp->flags & PP_CLAIMED) {
>  			dev_dbg(&pp->pdev->dev, "you've already got it!\n");
>  			return -EINVAL;
> @@ -517,15 +522,6 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> 
>  	port = pp->pdev->port;
>  	switch (cmd) {
> -		struct ieee1284_info *info;
> -		unsigned char reg;
> -		unsigned char mask;
> -		int mode;
> -		s32 time32[2];
> -		s64 time64[2];
> -		struct timespec64 ts;
> -		int ret;
> -
>  	case PPRSTATUS:
>  		reg = parport_read_status(port);
>  		if (copy_to_user(argp, &reg, sizeof(reg)))
> diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
> index b506e3622b08..8f93956c1628 100644
> --- a/drivers/gpu/drm/drm_edid.c
> +++ b/drivers/gpu/drm/drm_edid.c
> @@ -3942,12 +3942,12 @@ static void drm_edid_to_eld(struct drm_connector *connector, struct edid *edid)
>  		}
> 
>  		for_each_cea_db(cea, i, start, end) {
> +			int sad_count;
> +
>  			db = &cea[i];
>  			dbl = cea_db_payload_len(db);
> 
>  			switch (cea_db_tag(db)) {
> -				int sad_count;
> -
>  			case AUDIO_BLOCK:
>  				/* Audio Data Block, contains SADs */
>  				sad_count = min(dbl / 3, 15 - total_sad_count);
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 3da9c0f9e948..aa1c2ebea456 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -11341,6 +11341,7 @@ static bool check_digital_port_conflicts(struct drm_atomic_state *state)
>  	drm_for_each_connector_iter(connector, &conn_iter) {
>  		struct drm_connector_state *connector_state;
>  		struct intel_encoder *encoder;
> +		unsigned int port_mask;
> 
>  		connector_state = drm_atomic_get_new_connector_state(state, connector);
>  		if (!connector_state)
> @@ -11354,7 +11355,6 @@ static bool check_digital_port_conflicts(struct drm_atomic_state *state)
>  		WARN_ON(!connector_state->crtc);
> 
>  		switch (encoder->type) {
> -			unsigned int port_mask;
>  		case INTEL_OUTPUT_DDI:
>  			if (WARN_ON(!HAS_DDI(to_i915(dev))))
>  				break;
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index a26b4eddda25..c135fdec96b3 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -478,9 +478,9 @@ static void vlv_get_fifo_size(struct intel_crtc_state *crtc_state)
>  	struct vlv_fifo_state *fifo_state = &crtc_state->wm.vlv.fifo_state;
>  	enum pipe pipe = crtc->pipe;
>  	int sprite0_start, sprite1_start;
> +	uint32_t dsparb, dsparb2, dsparb3;
> 
>  	switch (pipe) {
> -		uint32_t dsparb, dsparb2, dsparb3;
>  	case PIPE_A:
>  		dsparb = I915_READ(DSPARB);
>  		dsparb2 = I915_READ(DSPARB2);
> @@ -1944,6 +1944,7 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
>  	const struct vlv_fifo_state *fifo_state =
>  		&crtc_state->wm.vlv.fifo_state;
>  	int sprite0_start, sprite1_start, fifo_size;
> +	uint32_t dsparb, dsparb2, dsparb3;
> 
>  	if (!crtc_state->fifo_changed)
>  		return;
> @@ -1969,7 +1970,6 @@ static void vlv_atomic_update_fifo(struct intel_atomic_state *state,
>  	spin_lock(&dev_priv->uncore.lock);
> 
>  	switch (crtc->pipe) {
> -		uint32_t dsparb, dsparb2, dsparb3;
>  	case PIPE_A:
>  		dsparb = I915_READ_FW(DSPARB);
>  		dsparb2 = I915_READ_FW(DSPARB2);
> diff --git a/drivers/net/ethernet/intel/e1000/e1000_main.c b/drivers/net/ethernet/intel/e1000/e1000_main.c
> index 8fe9af0e2ab7..041062736845 100644
> --- a/drivers/net/ethernet/intel/e1000/e1000_main.c
> +++ b/drivers/net/ethernet/intel/e1000/e1000_main.c
> @@ -3140,8 +3140,9 @@ static netdev_tx_t e1000_xmit_frame(struct sk_buff *skb,
> 
>  		hdr_len = skb_transport_offset(skb) + tcp_hdrlen(skb);
>  		if (skb->data_len && hdr_len == len) {
> +			unsigned int pull_size;
> +
>  			switch (hw->mac_type) {
> -				unsigned int pull_size;
>  			case e1000_82544:
>  				/* Make sure we have room to chop off 4 bytes,
>  				 * and that the end alignment will work out to
> diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
> index 5dc9686697cf..eafb39157281 100644
> --- a/drivers/tty/n_tty.c
> +++ b/drivers/tty/n_tty.c
> @@ -634,6 +634,7 @@ static size_t __process_echoes(struct tty_struct *tty)
>  	while (MASK(ldata->echo_commit) != MASK(tail)) {
>  		c = echo_buf(ldata, tail);
>  		if (c == ECHO_OP_START) {
> +			unsigned int num_chars, num_bs;
>  			unsigned char op;
>  			int no_space_left = 0;
> 
> @@ -652,8 +653,6 @@ static size_t __process_echoes(struct tty_struct *tty)
>  			op = echo_buf(ldata, tail + 1);
> 
>  			switch (op) {
> -				unsigned int num_chars, num_bs;
> -
>  			case ECHO_OP_ERASE_TAB:
>  				if (MASK(ldata->echo_commit) == MASK(tail + 2))
>  					goto not_yet_stored;
> diff --git a/drivers/usb/gadget/udc/net2280.c b/drivers/usb/gadget/udc/net2280.c
> index e7dae5379e04..2b275a574e94 100644
> --- a/drivers/usb/gadget/udc/net2280.c
> +++ b/drivers/usb/gadget/udc/net2280.c
> @@ -2854,16 +2854,15 @@ static void ep_clear_seqnum(struct net2280_ep *ep)
>  static void handle_stat0_irqs_superspeed(struct net2280 *dev,
>  		struct net2280_ep *ep, struct usb_ctrlrequest r)
>  {
> +	struct net2280_ep *e;
>  	int tmp = 0;
> +	u16 status;
> 
>  #define	w_value		le16_to_cpu(r.wValue)
>  #define	w_index		le16_to_cpu(r.wIndex)
>  #define	w_length	le16_to_cpu(r.wLength)
> 
>  	switch (r.bRequest) {
> -		struct net2280_ep *e;
> -		u16 status;
> -
>  	case USB_REQ_SET_CONFIGURATION:
>  		dev->addressed_state = !w_value;
>  		goto usb3_delegate;
> diff --git a/fs/fcntl.c b/fs/fcntl.c
> index 083185174c6d..0640b64ecdc2 100644
> --- a/fs/fcntl.c
> +++ b/fs/fcntl.c
> @@ -725,6 +725,8 @@ static void send_sigio_to_task(struct task_struct *p,
>  			       struct fown_struct *fown,
>  			       int fd, int reason, enum pid_type type)
>  {
> +	kernel_siginfo_t si;
> +
>  	/*
>  	 * F_SETSIG can change ->signum lockless in parallel, make
>  	 * sure we read it once and use the same value throughout.
> @@ -735,7 +737,6 @@ static void send_sigio_to_task(struct task_struct *p,
>  		return;
> 
>  	switch (signum) {
> -		kernel_siginfo_t si;
>  		default:
>  			/* Queue a rt signal with the appropriate fd as its
>  			   value.  We use SI_SIGIO as the source, not
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 6ece1e2fe76e..0b02624dd8b2 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -1721,6 +1721,9 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
>  		swap_free(swap);
> 
>  	} else {
> +		loff_t i_size;
> +		pgoff_t off;
> +
>  		if (vma && userfaultfd_missing(vma)) {
>  			*fault_type = handle_userfault(vmf, VM_UFFD_MISSING);
>  			return 0;
> @@ -1734,8 +1737,6 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
>  		if (shmem_huge == SHMEM_HUGE_FORCE)
>  			goto alloc_huge;
>  		switch (sbinfo->huge) {
> -			loff_t i_size;
> -			pgoff_t off;
>  		case SHMEM_HUGE_NEVER:
>  			goto alloc_nohuge;
>  		case SHMEM_HUGE_WITHIN_SIZE:
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 26d848484912..7597b3fc9d21 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -4506,9 +4506,9 @@ static __sum16 *skb_checksum_setup_ip(struct sk_buff *skb,
>  				      typeof(IPPROTO_IP) proto,
>  				      unsigned int off)
>  {
> -	switch (proto) {
> -		int err;
> +	int err;
> 
> +	switch (proto) {
>  	case IPPROTO_TCP:
>  		err = skb_maybe_pull_tail(skb, off + sizeof(struct tcphdr),
>  					  off + MAX_TCP_HDR_LEN);
> diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
> index b1be67ca6768..9aee1add46c0 100644
> --- a/net/ipv6/ip6_gre.c
> +++ b/net/ipv6/ip6_gre.c
> @@ -427,9 +427,11 @@ static int ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
>  		       u8 type, u8 code, int offset, __be32 info)
>  {
>  	struct net *net = dev_net(skb->dev);
> +	struct ipv6_tlv_tnl_enc_lim *tel;
>  	const struct ipv6hdr *ipv6h;
>  	struct tnl_ptk_info tpi;
>  	struct ip6_tnl *t;
> +	__u32 teli;
> 
>  	if (gre_parse_header(skb, &tpi, NULL, htons(ETH_P_IPV6),
>  			     offset) < 0)
> @@ -442,8 +444,6 @@ static int ip6gre_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
>  		return -ENOENT;
> 
>  	switch (type) {
> -		struct ipv6_tlv_tnl_enc_lim *tel;
> -		__u32 teli;
>  	case ICMPV6_DEST_UNREACH:
>  		net_dbg_ratelimited("%s: Path to destination invalid or inactive!\n",
>  				    t->parms.name);
> diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
> index 0c6403cf8b52..94ccc7a9037b 100644
> --- a/net/ipv6/ip6_tunnel.c
> +++ b/net/ipv6/ip6_tunnel.c
> @@ -478,10 +478,12 @@ ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,
>  	struct net *net = dev_net(skb->dev);
>  	u8 rel_type = ICMPV6_DEST_UNREACH;
>  	u8 rel_code = ICMPV6_ADDR_UNREACH;
> +	struct ipv6_tlv_tnl_enc_lim *tel;
>  	__u32 rel_info = 0;
>  	struct ip6_tnl *t;
>  	int err = -ENOENT;
>  	int rel_msg = 0;
> +	__u32 mtu, teli;
>  	u8 tproto;
>  	__u16 len;
> 
> @@ -501,8 +503,6 @@ ip6_tnl_err(struct sk_buff *skb, __u8 ipproto, struct inet6_skb_parm *opt,
>  	err = 0;
> 
>  	switch (*type) {
> -		struct ipv6_tlv_tnl_enc_lim *tel;
> -		__u32 mtu, teli;
>  	case ICMPV6_DEST_UNREACH:
>  		net_dbg_ratelimited("%s: Path to destination invalid or inactive!\n",
>  				    t->parms.name);
> diff --git a/net/openvswitch/flow_netlink.c b/net/openvswitch/flow_netlink.c
> index 691da853bef5..dee2f9516ae8 100644
> --- a/net/openvswitch/flow_netlink.c
> +++ b/net/openvswitch/flow_netlink.c
> @@ -2652,8 +2652,11 @@ static int validate_set(const struct nlattr *a,
>  			u8 mac_proto, __be16 eth_type, bool masked, bool log)
>  {
>  	const struct nlattr *ovs_key = nla_data(a);
> +	const struct ovs_key_ipv4 *ipv4_key;
> +	const struct ovs_key_ipv6 *ipv6_key;
>  	int key_type = nla_type(ovs_key);
>  	size_t key_len;
> +	int err;
> 
>  	/* There can be only one key in a action */
>  	if (nla_total_size(nla_len(ovs_key)) != nla_len(a))
> @@ -2671,10 +2674,6 @@ static int validate_set(const struct nlattr *a,
>  		return -EINVAL;
> 
>  	switch (key_type) {
> -	const struct ovs_key_ipv4 *ipv4_key;
> -	const struct ovs_key_ipv6 *ipv6_key;
> -	int err;
> -
>  	case OVS_KEY_ATTR_PRIORITY:
>  	case OVS_KEY_ATTR_SKB_MARK:
>  	case OVS_KEY_ATTR_CT_MARK:
> diff --git a/security/tomoyo/common.c b/security/tomoyo/common.c
> index c598aa00d5e3..bedbd0518153 100644
> --- a/security/tomoyo/common.c
> +++ b/security/tomoyo/common.c
> @@ -1583,8 +1583,9 @@ static void tomoyo_read_domain(struct tomoyo_io_buffer *head)
>  	list_for_each_cookie(head->r.domain, &tomoyo_domain_list) {
>  		struct tomoyo_domain_info *domain =
>  			list_entry(head->r.domain, typeof(*domain), list);
> +		u8 i;
> +
>  		switch (head->r.step) {
> -			u8 i;
>  		case 0:
>  			if (domain->is_deleted &&
>  			    !head->r.print_this_domain_only)
> diff --git a/security/tomoyo/condition.c b/security/tomoyo/condition.c
> index 8d0e1b9c9c57..c10d903febe5 100644
> --- a/security/tomoyo/condition.c
> +++ b/security/tomoyo/condition.c
> @@ -787,10 +787,11 @@ bool tomoyo_condition(struct tomoyo_request_info *r,
>  		/* Check string expressions. */
>  		if (right == TOMOYO_NAME_UNION) {
>  			const struct tomoyo_name_union *ptr = names_p++;
> +			struct tomoyo_path_info *symlink;
> +			struct tomoyo_execve *ee;
> +			struct file *file;
> +
>  			switch (left) {
> -				struct tomoyo_path_info *symlink;
> -				struct tomoyo_execve *ee;
> -				struct file *file;
>  			case TOMOYO_SYMLINK_TARGET:
>  				symlink = obj ? obj->symlink_target : NULL;
>  				if (!symlink ||
> diff --git a/security/tomoyo/util.c b/security/tomoyo/util.c
> index badffc8271c8..8e2bb36df37b 100644
> --- a/security/tomoyo/util.c
> +++ b/security/tomoyo/util.c
> @@ -668,6 +668,8 @@ static bool tomoyo_file_matches_pattern2(const char *filename,
>  {
>  	while (filename < filename_end && pattern < pattern_end) {
>  		char c;
> +		int i, j;
> +
>  		if (*pattern != '\\') {
>  			if (*filename++ != *pattern++)
>  				return false;
> @@ -676,8 +678,6 @@ static bool tomoyo_file_matches_pattern2(const char *filename,
>  		c = *filename;
>  		pattern++;
>  		switch (*pattern) {
> -			int i;
> -			int j;
>  		case '?':
>  			if (c == '/') {
>  				return false;
> --
> 2.17.1


^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 0/3] gcc-plugins: Introduce stackinit plugin
  2019-01-23 11:03 [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Kees Cook
                   ` (2 preceding siblings ...)
  2019-01-23 11:03 ` [PATCH 3/3] lib: Introduce test_stackinit module Kees Cook
@ 2019-01-29  0:12 ` Alexander Popov
  2019-02-12 17:54   ` Kees Cook
  3 siblings, 1 reply; 20+ messages in thread
From: Alexander Popov @ 2019-01-29  0:12 UTC (permalink / raw)
  To: Kees Cook, linux-kernel
  Cc: Ard Biesheuvel, Laura Abbott, xen-devel, dri-devel, intel-gfx,
	intel-wired-lan, netdev, linux-usb, linux-fsdevel, linux-mm, dev,
	linux-kbuild, linux-security-module, kernel-hardening, Greg KH,
	Jann Horn, William Kucharski, Jani Nikula, Edwin Zimmerman,
	Matthew Wilcox, Jeff Kirsher

On 23.01.2019 14:03, Kees Cook wrote:
> This adds a new plugin "stackinit" that attempts to perform unconditional
> initialization of all stack variables

Hello Kees! Hello everyone!

I was curious about the performance impact of the initialization of all stack
variables. So I did a very brief test with this plugin on top of 4.20.5.

hackbench on Intel Core i7-4770 showed ~0.7% slowdown.
hackbench on Kirin 620 (ARM Cortex-A53 Octa-core 1.2GHz) showed ~1.3% slowdown.

This test involves the kernel scheduler and allocator. I can't say whether they
use stack aggressively. Maybe performance tests of other subsystems (e.g.
network subsystem) can show different numbers. Did you try?

I've heard a hypothesis that the initialization of all stack variables would
pollute CPU caches, which is critical for some types of computations. Maybe some
micro-benchmarks can disprove/confirm that?

Thanks!
Best regards,
Alexander

^ permalink raw reply	[flat|nested] 20+ messages in thread

* Re: [PATCH 0/3] gcc-plugins: Introduce stackinit plugin
  2019-01-29  0:12 ` [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Alexander Popov
@ 2019-02-12 17:54   ` Kees Cook
  0 siblings, 0 replies; 20+ messages in thread
From: Kees Cook @ 2019-02-12 17:54 UTC (permalink / raw)
  To: Alexander Popov
  Cc: LKML, Ard Biesheuvel, Laura Abbott, xen-devel,
	Maling list - DRI developers, intel-gfx, intel-wired-lan,
	Network Development, linux-usb, linux-fsdevel, Linux-MM, dev,
	linux-kbuild, linux-security-module, Kernel Hardening, Greg KH,
	Jann Horn, William Kucharski, Jani Nikula, Edwin Zimmerman,
	Matthew Wilcox, Jeff Kirsher

On Mon, Jan 28, 2019 at 4:12 PM Alexander Popov <alex.popov@linux.com> wrote:
>
> On 23.01.2019 14:03, Kees Cook wrote:
> > This adds a new plugin "stackinit" that attempts to perform unconditional
> > initialization of all stack variables
>
> Hello Kees! Hello everyone!
>
> I was curious about the performance impact of the initialization of all stack
> variables. So I did a very brief test with this plugin on top of 4.20.5.
>
> hackbench on Intel Core i7-4770 showed ~0.7% slowdown.
> hackbench on Kirin 620 (ARM Cortex-A53 Octa-core 1.2GHz) showed ~1.3% slowdown.

Thanks for looking at this! I'll be including my hackbench
measurements for the v2 here in a moment.

> This test involves the kernel scheduler and allocator. I can't say whether they
> use stack aggressively. Maybe performance tests of other subsystems (e.g.
> network subsystem) can show different numbers. Did you try?

I haven't found a stable network test yet. If someone can find a
reasonable workload, I'd love to hear about it.

> I've heard a hypothesis that the initialization of all stack variables would
> pollute CPU caches, which is critical for some types of computations. Maybe some
> micro-benchmarks can disprove/confirm that?

I kind of think micro-benchmarks aren't so useful because they don't
represent a real-world workload. I've heard people talk about SAP-HANA
as a good test, but I can't get my hands on it. I wonder if anyone has
tried "mysqlslap"?

-- 
Kees Cook

^ permalink raw reply	[flat|nested] 20+ messages in thread

end of thread, other threads:[~2019-02-12 17:54 UTC | newest]

Thread overview: 20+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-01-23 11:03 [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Kees Cook
2019-01-23 11:03 ` [PATCH 1/3] treewide: Lift switch variables out of switches Kees Cook
2019-01-23 11:58   ` Greg KH
2019-01-23 12:09     ` Jann Horn
2019-01-23 12:12       ` Ard Biesheuvel
2019-01-23 13:21       ` William Kucharski
2019-01-23 14:17     ` [Intel-gfx] " Jani Nikula
2019-01-23 14:23       ` Jani Nikula
2019-01-23 14:47       ` Edwin Zimmerman
2019-01-23 15:46         ` Jani Nikula
2019-01-23 18:55           ` Kees Cook
2019-01-24  8:10             ` Greg KH
2019-01-23 19:18       ` Matthew Wilcox
2019-01-23 20:36         ` Kees Cook
2019-01-23 16:51   ` [Intel-wired-lan] " Jeff Kirsher
2019-01-24 12:58   ` Edwin Zimmerman
2019-01-23 11:03 ` [PATCH 2/3] gcc-plugins: Introduce stackinit plugin Kees Cook
2019-01-23 11:03 ` [PATCH 3/3] lib: Introduce test_stackinit module Kees Cook
2019-01-29  0:12 ` [PATCH 0/3] gcc-plugins: Introduce stackinit plugin Alexander Popov
2019-02-12 17:54   ` Kees Cook

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