Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 12fa8a27 authored by James Morris's avatar James Morris
Browse files

Merge branch 'for-1205' of http://git.gitorious.org/smack-next/kernel into next

Pull request from Casey.
parents b404aef7 f7112e6c
Loading
Loading
Loading
Loading
+164 −40
Original line number Diff line number Diff line
@@ -15,7 +15,7 @@ at hand.

Smack consists of three major components:
    - The kernel
    - A start-up script and a few modified applications
    - Basic utilities, which are helpful but not required
    - Configuration data

The kernel component of Smack is implemented as a Linux
@@ -23,37 +23,28 @@ Security Modules (LSM) module. It requires netlabel and
works best with file systems that support extended attributes,
although xattr support is not strictly required.
It is safe to run a Smack kernel under a "vanilla" distribution.

Smack kernels use the CIPSO IP option. Some network
configurations are intolerant of IP options and can impede
access to systems that use them as Smack does.

The startup script etc-init.d-smack should be installed
in /etc/init.d/smack and should be invoked early in the
start-up process. On Fedora rc5.d/S02smack is recommended.
This script ensures that certain devices have the correct
Smack attributes and loads the Smack configuration if
any is defined. This script invokes two programs that
ensure configuration data is properly formatted. These
programs are /usr/sbin/smackload and /usr/sin/smackcipso.
The system will run just fine without these programs,
but it will be difficult to set access rules properly.

A version of "ls" that provides a "-M" option to display
Smack labels on long listing is available.
The current git repositories for Smack user space are:

A hacked version of sshd that allows network logins by users
with specific Smack labels is available. This version does
not work for scp. You must set the /etc/ssh/sshd_config
line:
   UsePrivilegeSeparation no
	git@gitorious.org:meego-platform-security/smackutil.git
	git@gitorious.org:meego-platform-security/libsmack.git

The format of /etc/smack/usr is:
These should make and install on most modern distributions.
There are three commands included in smackutil:

   username smack
smackload  - properly formats data for writing to /smack/load
smackcipso - properly formats data for writing to /smack/cipso
chsmack    - display or set Smack extended attribute values

In keeping with the intent of Smack, configuration data is
minimal and not strictly required. The most important
configuration step is mounting the smackfs pseudo filesystem.
If smackutil is installed the startup script will take care
of this, but it can be manually as well.

Add this line to /etc/fstab:

@@ -61,19 +52,148 @@ Add this line to /etc/fstab:

and create the /smack directory for mounting.

Smack uses extended attributes (xattrs) to store file labels.
The command to set a Smack label on a file is:
Smack uses extended attributes (xattrs) to store labels on filesystem
objects. The attributes are stored in the extended attribute security
name space. A process must have CAP_MAC_ADMIN to change any of these
attributes.

The extended attributes that Smack uses are:

SMACK64
	Used to make access control decisions. In almost all cases
	the label given to a new filesystem object will be the label
	of the process that created it.
SMACK64EXEC
	The Smack label of a process that execs a program file with
	this attribute set will run with this attribute's value.
SMACK64MMAP
	Don't allow the file to be mmapped by a process whose Smack
	label does not allow all of the access permitted to a process
	with the label contained in this attribute. This is a very
	specific use case for shared libraries.
SMACK64TRANSMUTE
	Can only have the value "TRUE". If this attribute is present
	on a directory when an object is created in the directory and
	the Smack rule (more below) that permitted the write access
	to the directory includes the transmute ("t") mode the object
	gets the label of the directory instead of the label of the
	creating process. If the object being created is a directory
	the SMACK64TRANSMUTE attribute is set as well.
SMACK64IPIN
	This attribute is only available on file descriptors for sockets.
	Use the Smack label in this attribute for access control
	decisions on packets being delivered to this socket.
SMACK64IPOUT
	This attribute is only available on file descriptors for sockets.
	Use the Smack label in this attribute for access control
	decisions on packets coming from this socket.

There are multiple ways to set a Smack label on a file:

    # attr -S -s SMACK64 -V "value" path
    # chsmack -a value path

NOTE: Smack labels are limited to 23 characters. The attr command
      does not enforce this restriction and can be used to set
      invalid Smack labels on files.

If you don't do anything special all users will get the floor ("_")
label when they log in. If you do want to log in via the hacked ssh
at other labels use the attr command to set the smack value on the
home directory and its contents.
A process can see the smack label it is running with by
reading /proc/self/attr/current. A process with CAP_MAC_ADMIN
can set the process smack by writing there.

Most Smack configuration is accomplished by writing to files
in the smackfs filesystem. This pseudo-filesystem is usually
mounted on /smack.

access
	This interface reports whether a subject with the specified
	Smack label has a particular access to an object with a
	specified Smack label. Write a fixed format access rule to
	this file. The next read will indicate whether the access
	would be permitted. The text will be either "1" indicating
	access, or "0" indicating denial.
access2
	This interface reports whether a subject with the specified
	Smack label has a particular access to an object with a
	specified Smack label. Write a long format access rule to
	this file. The next read will indicate whether the access
	would be permitted. The text will be either "1" indicating
	access, or "0" indicating denial.
ambient
	This contains the Smack label applied to unlabeled network
	packets.
cipso
	This interface allows a specific CIPSO header to be assigned
	to a Smack label. The format accepted on write is:
		"%24s%4d%4d"["%4d"]...
	The first string is a fixed Smack label. The first number is
	the level to use. The second number is the number of categories.
	The following numbers are the categories.
	"level-3-cats-5-19          3   2   5  19"
cipso2
	This interface allows a specific CIPSO header to be assigned
	to a Smack label. The format accepted on write is:
	"%s%4d%4d"["%4d"]...
	The first string is a long Smack label. The first number is
	the level to use. The second number is the number of categories.
	The following numbers are the categories.
	"level-3-cats-5-19   3   2   5  19"
direct
	This contains the CIPSO level used for Smack direct label
	representation in network packets.
doi
	This contains the CIPSO domain of interpretation used in
	network packets.
load
	This interface allows access control rules in addition to
	the system defined rules to be specified. The format accepted
	on write is:
		"%24s%24s%5s"
	where the first string is the subject label, the second the
	object label, and the third the requested access. The access
	string may contain only the characters "rwxat-", and specifies
	which sort of access is allowed. The "-" is a placeholder for
	permissions that are not allowed. The string "r-x--" would
	specify read and execute access. Labels are limited to 23
	characters in length.
load2
	This interface allows access control rules in addition to
	the system defined rules to be specified. The format accepted
	on write is:
		"%s %s %s"
	where the first string is the subject label, the second the
	object label, and the third the requested access. The access
	string may contain only the characters "rwxat-", and specifies
	which sort of access is allowed. The "-" is a placeholder for
	permissions that are not allowed. The string "r-x--" would
	specify read and execute access.
load-self
	This interface allows process specific access rules to be
	defined. These rules are only consulted if access would
	otherwise be permitted, and are intended to provide additional
	restrictions on the process. The format is the same as for
	the load interface.
load-self2
	This interface allows process specific access rules to be
	defined. These rules are only consulted if access would
	otherwise be permitted, and are intended to provide additional
	restrictions on the process. The format is the same as for
	the load2 interface.
logging
	This contains the Smack logging state.
mapped
	This contains the CIPSO level used for Smack mapped label
	representation in network packets.
netlabel
	This interface allows specific internet addresses to be
	treated as single label hosts. Packets are sent to single
	label hosts without CIPSO headers, but only from processes
	that have Smack write access to the host label. All packets
	received from single label hosts are given the specified
	label. The format accepted on write is:
		"%d.%d.%d.%d label" or "%d.%d.%d.%d/%d label".
onlycap
	This contains the label processes must have for CAP_MAC_ADMIN
	and CAP_MAC_OVERRIDE to be effective. If this file is empty
	these capabilities are effective at for processes with any
	label. The value is set by writing the desired label to the
	file or cleared by writing "-" to the file.

You can add access rules in /etc/smack/accesses. They take the form:

@@ -83,10 +203,6 @@ access is a combination of the letters rwxa which specify the
kind of access permitted a subject with subjectlabel on an
object with objectlabel. If there is no rule no access is allowed.

A process can see the smack label it is running with by
reading /proc/self/attr/current. A privileged process can
set the process smack by writing there.

Look for additional programs on http://schaufler-ca.com

From the Smack Whitepaper:
@@ -186,7 +302,7 @@ team. Smack labels are unstructured, case sensitive, and the only operation
ever performed on them is comparison for equality. Smack labels cannot
contain unprintable characters, the "/" (slash), the "\" (backslash), the "'"
(quote) and '"' (double-quote) characters.
Smack labels cannot begin with a '-', which is reserved for special options.
Smack labels cannot begin with a '-'. This is reserved for special options.

There are some predefined labels:

@@ -194,7 +310,7 @@ There are some predefined labels:
	^ 	Pronounced "hat", a single circumflex character.
	* 	Pronounced "star", a single asterisk character.
	? 	Pronounced "huh", a single question mark character.
	@ 	Pronounced "Internet", a single at sign character.
	@ 	Pronounced "web", a single at sign character.

Every task on a Smack system is assigned a label. System tasks, such as
init(8) and systems daemons, are run with the floor ("_") label. User tasks
@@ -246,13 +362,14 @@ The format of an access rule is:

Where subject-label is the Smack label of the task, object-label is the Smack
label of the thing being accessed, and access is a string specifying the sort
of access allowed. The Smack labels are limited to 23 characters. The access
specification is searched for letters that describe access modes:
of access allowed. The access specification is searched for letters that
describe access modes:

	a: indicates that append access should be granted.
	r: indicates that read access should be granted.
	w: indicates that write access should be granted.
	x: indicates that execute access should be granted.
	t: indicates that the rule requests transmutation.

Uppercase values for the specification letters are allowed as well.
Access mode specifications can be in any order. Examples of acceptable rules
@@ -273,7 +390,7 @@ Examples of unacceptable rules are:

Spaces are not allowed in labels. Since a subject always has access to files
with the same label specifying a rule for that case is pointless. Only
valid letters (rwxaRWXA) and the dash ('-') character are allowed in
valid letters (rwxatRWXAT) and the dash ('-') character are allowed in
access specifications. The dash is a placeholder, so "a-r" is the same
as "ar". A lone dash is used to specify that no access should be allowed.

@@ -297,6 +414,13 @@ but not any of its attributes by the circumstance of having read access to the
containing directory but not to the differently labeled file. This is an
artifact of the file name being data in the directory, not a part of the file.

If a directory is marked as transmuting (SMACK64TRANSMUTE=TRUE) and the
access rule that allows a process to create an object in that directory
includes 't' access the label assigned to the new object will be that
of the directory, not the creating process. This makes it much easier
for two processes with different labels to share data without granting
access to all of their files.

IPC objects, message queues, semaphore sets, and memory segments exist in flat
namespaces and access requests are only required to match the object in
question.
+21 −36
Original line number Diff line number Diff line
@@ -23,13 +23,19 @@
#include <linux/lsm_audit.h>

/*
 * Smack labels were limited to 23 characters for a long time.
 */
#define SMK_LABELLEN	24
#define SMK_LONGLABEL	256

/*
 * Maximum number of bytes for the levels in a CIPSO IP option.
 * Why 23? CIPSO is constrained to 30, so a 32 byte buffer is
 * bigger than can be used, and 24 is the next lower multiple
 * of 8, and there are too many issues if there isn't space set
 * aside for the terminating null byte.
 */
#define SMK_MAXLEN	23
#define SMK_LABELLEN	(SMK_MAXLEN+1)
#define SMK_CIPSOLEN	24

struct superblock_smack {
	char		*smk_root;
@@ -66,6 +72,7 @@ struct task_smack {

#define	SMK_INODE_INSTANT	0x01	/* inode is instantiated */
#define	SMK_INODE_TRANSMUTE	0x02	/* directory is transmuting */
#define	SMK_INODE_CHANGED	0x04	/* smack was transmuted */

/*
 * A label access rule.
@@ -77,15 +84,6 @@ struct smack_rule {
	int			smk_access;
};

/*
 * An entry in the table mapping smack values to
 * CIPSO level/category-set values.
 */
struct smack_cipso {
	int	smk_level;
	char	smk_catset[SMK_LABELLEN];
};

/*
 * An entry in the table identifying hosts.
 */
@@ -113,9 +111,7 @@ struct smk_netlbladdr {
 * interfaces don't. The secid should go away when all of
 * these components have been repaired.
 *
 * If there is a cipso value associated with the label it
 * gets stored here, too. This will most likely be rare as
 * the cipso direct mapping in used internally.
 * The cipso value associated with the label gets stored here, too.
 *
 * Keep the access rules for this subject label here so that
 * the entire set of rules does not need to be examined every
@@ -123,12 +119,11 @@ struct smk_netlbladdr {
 */
struct smack_known {
	struct list_head		list;
	char			smk_known[SMK_LABELLEN];
	char				*smk_known;
	u32				smk_secid;
	struct smack_cipso	*smk_cipso;
	spinlock_t		smk_cipsolock;	/* for changing cipso map */
	struct netlbl_lsm_secattr	smk_netlabel;	/* on wire labels */
	struct list_head		smk_rules;	/* access rules */
	struct mutex		smk_rules_lock;	/* lock for the rules */
	struct mutex			smk_rules_lock;	/* lock for rules */
};

/*
@@ -165,6 +160,7 @@ struct smack_known {
#define SMACK_CIPSO_DOI_DEFAULT		3	/* Historical */
#define SMACK_CIPSO_DOI_INVALID		-1	/* Not a DOI */
#define SMACK_CIPSO_DIRECT_DEFAULT	250	/* Arbitrary */
#define SMACK_CIPSO_MAPPED_DEFAULT	251	/* Also arbitrary */
#define SMACK_CIPSO_MAXCATVAL		63	/* Bigger gets harder */
#define SMACK_CIPSO_MAXLEVEL            255     /* CIPSO 2.2 standard */
#define SMACK_CIPSO_MAXCATNUM           239     /* CIPSO 2.2 standard */
@@ -215,10 +211,9 @@ struct inode_smack *new_inode_smack(char *);
int smk_access_entry(char *, char *, struct list_head *);
int smk_access(char *, char *, int, struct smk_audit_info *);
int smk_curacc(char *, u32, struct smk_audit_info *);
int smack_to_cipso(const char *, struct smack_cipso *);
char *smack_from_cipso(u32, char *);
char *smack_from_secid(const u32);
void smk_parse_smack(const char *string, int len, char *smack);
char *smk_parse_smack(const char *string, int len);
int smk_netlbl_mls(int, char *, struct netlbl_lsm_secattr *, int);
char *smk_import(const char *, int);
struct smack_known *smk_import_entry(const char *, int);
struct smack_known *smk_find_entry(const char *);
@@ -228,6 +223,7 @@ u32 smack_to_secid(const char *);
 * Shared data.
 */
extern int smack_cipso_direct;
extern int smack_cipso_mapped;
extern char *smack_net_ambient;
extern char *smack_onlycap;
extern const char *smack_cipso_option;
@@ -239,23 +235,12 @@ extern struct smack_known smack_known_invalid;
extern struct smack_known smack_known_star;
extern struct smack_known smack_known_web;

extern struct mutex	smack_known_lock;
extern struct list_head smack_known_list;
extern struct list_head smk_netlbladdr_list;

extern struct security_operations smack_ops;

/*
 * Stricly for CIPSO level manipulation.
 * Set the category bit number in a smack label sized buffer.
 */
static inline void smack_catset_bit(int cat, char *catsetp)
{
	if (cat > SMK_LABELLEN * 8)
		return;

	catsetp[(cat - 1) / 8] |= 0x80 >> ((cat - 1) % 8);
}

/*
 * Is the directory transmuting?
 */
+116 −117
Original line number Diff line number Diff line
@@ -19,37 +19,31 @@
struct smack_known smack_known_huh = {
	.smk_known	= "?",
	.smk_secid	= 2,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_hat = {
	.smk_known	= "^",
	.smk_secid	= 3,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_star = {
	.smk_known	= "*",
	.smk_secid	= 4,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_floor = {
	.smk_known	= "_",
	.smk_secid	= 5,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_invalid = {
	.smk_known	= "",
	.smk_secid	= 6,
	.smk_cipso	= NULL,
};

struct smack_known smack_known_web = {
	.smk_known	= "@",
	.smk_secid	= 7,
	.smk_cipso	= NULL,
};

LIST_HEAD(smack_known_list);
@@ -331,7 +325,7 @@ void smack_log(char *subject_label, char *object_label, int request,
}
#endif

static DEFINE_MUTEX(smack_known_lock);
DEFINE_MUTEX(smack_known_lock);

/**
 * smk_find_entry - find a label on the list, return the list entry
@@ -345,7 +339,7 @@ struct smack_known *smk_find_entry(const char *string)
	struct smack_known *skp;

	list_for_each_entry_rcu(skp, &smack_known_list, list) {
		if (strncmp(skp->smk_known, string, SMK_MAXLEN) == 0)
		if (strcmp(skp->smk_known, string) == 0)
			return skp;
	}

@@ -356,27 +350,76 @@ struct smack_known *smk_find_entry(const char *string)
 * smk_parse_smack - parse smack label from a text string
 * @string: a text string that might contain a Smack label
 * @len: the maximum size, or zero if it is NULL terminated.
 * @smack: parsed smack label, or NULL if parse error
 *
 * Returns a pointer to the clean label, or NULL
 */
void smk_parse_smack(const char *string, int len, char *smack)
char *smk_parse_smack(const char *string, int len)
{
	int found;
	char *smack;
	int i;

	if (len <= 0 || len > SMK_MAXLEN)
		len = SMK_MAXLEN;
	if (len <= 0)
		len = strlen(string) + 1;

	for (i = 0, found = 0; i < SMK_LABELLEN; i++) {
		if (found)
			smack[i] = '\0';
		else if (i >= len || string[i] > '~' || string[i] <= ' ' ||
			 string[i] == '/' || string[i] == '"' ||
			 string[i] == '\\' || string[i] == '\'') {
	/*
	 * Reserve a leading '-' as an indicator that
	 * this isn't a label, but an option to interfaces
	 * including /smack/cipso and /smack/cipso2
	 */
	if (string[0] == '-')
		return NULL;

	for (i = 0; i < len; i++)
		if (string[i] > '~' || string[i] <= ' ' || string[i] == '/' ||
		    string[i] == '"' || string[i] == '\\' || string[i] == '\'')
			break;

	if (i == 0 || i >= SMK_LONGLABEL)
		return NULL;

	smack = kzalloc(i + 1, GFP_KERNEL);
	if (smack != NULL) {
		strncpy(smack, string, i + 1);
		smack[i] = '\0';
			found = 1;
		} else
			smack[i] = string[i];
	}
	return smack;
}

/**
 * smk_netlbl_mls - convert a catset to netlabel mls categories
 * @catset: the Smack categories
 * @sap: where to put the netlabel categories
 *
 * Allocates and fills attr.mls
 * Returns 0 on success, error code on failure.
 */
int smk_netlbl_mls(int level, char *catset, struct netlbl_lsm_secattr *sap,
			int len)
{
	unsigned char *cp;
	unsigned char m;
	int cat;
	int rc;
	int byte;

	sap->flags |= NETLBL_SECATTR_MLS_CAT;
	sap->attr.mls.lvl = level;
	sap->attr.mls.cat = netlbl_secattr_catmap_alloc(GFP_ATOMIC);
	sap->attr.mls.cat->startbit = 0;

	for (cat = 1, cp = catset, byte = 0; byte < len; cp++, byte++)
		for (m = 0x80; m != 0; m >>= 1, cat++) {
			if ((m & *cp) == 0)
				continue;
			rc = netlbl_secattr_catmap_setbit(sap->attr.mls.cat,
							  cat, GFP_ATOMIC);
			if (rc < 0) {
				netlbl_secattr_catmap_free(sap->attr.mls.cat);
				return rc;
			}
		}

	return 0;
}

/**
@@ -390,33 +433,59 @@ void smk_parse_smack(const char *string, int len, char *smack)
struct smack_known *smk_import_entry(const char *string, int len)
{
	struct smack_known *skp;
	char smack[SMK_LABELLEN];
	char *smack;
	int slen;
	int rc;

	smk_parse_smack(string, len, smack);
	if (smack[0] == '\0')
	smack = smk_parse_smack(string, len);
	if (smack == NULL)
		return NULL;

	mutex_lock(&smack_known_lock);

	skp = smk_find_entry(smack);
	if (skp != NULL)
		goto freeout;

	if (skp == NULL) {
		skp = kzalloc(sizeof(struct smack_known), GFP_KERNEL);
		if (skp != NULL) {
			strncpy(skp->smk_known, smack, SMK_MAXLEN);
	skp = kzalloc(sizeof(*skp), GFP_KERNEL);
	if (skp == NULL)
		goto freeout;

	skp->smk_known = smack;
	skp->smk_secid = smack_next_secid++;
			skp->smk_cipso = NULL;
	skp->smk_netlabel.domain = skp->smk_known;
	skp->smk_netlabel.flags =
		NETLBL_SECATTR_DOMAIN | NETLBL_SECATTR_MLS_LVL;
	/*
	 * If direct labeling works use it.
	 * Otherwise use mapped labeling.
	 */
	slen = strlen(smack);
	if (slen < SMK_CIPSOLEN)
		rc = smk_netlbl_mls(smack_cipso_direct, skp->smk_known,
			       &skp->smk_netlabel, slen);
	else
		rc = smk_netlbl_mls(smack_cipso_mapped, (char *)&skp->smk_secid,
			       &skp->smk_netlabel, sizeof(skp->smk_secid));

	if (rc >= 0) {
		INIT_LIST_HEAD(&skp->smk_rules);
			spin_lock_init(&skp->smk_cipsolock);
		mutex_init(&skp->smk_rules_lock);
		/*
		 * Make sure that the entry is actually
		 * filled before putting it on the list.
		 */
		list_add_rcu(&skp->list, &smack_known_list);
		goto unlockout;
	}
	}

	/*
	 * smk_netlbl_mls failed.
	 */
	kfree(skp);
	skp = NULL;
freeout:
	kfree(smack);
unlockout:
	mutex_unlock(&smack_known_lock);

	return skp;
@@ -479,79 +548,9 @@ char *smack_from_secid(const u32 secid)
 */
u32 smack_to_secid(const char *smack)
{
	struct smack_known *skp;

	rcu_read_lock();
	list_for_each_entry_rcu(skp, &smack_known_list, list) {
		if (strncmp(skp->smk_known, smack, SMK_MAXLEN) == 0) {
			rcu_read_unlock();
			return skp->smk_secid;
		}
	}
	rcu_read_unlock();
	return 0;
}

/**
 * smack_from_cipso - find the Smack label associated with a CIPSO option
 * @level: Bell & LaPadula level from the network
 * @cp: Bell & LaPadula categories from the network
 *
 * This is a simple lookup in the label table.
 *
 * Return the matching label from the label list or NULL.
 */
char *smack_from_cipso(u32 level, char *cp)
{
	struct smack_known *kp;
	char *final = NULL;

	rcu_read_lock();
	list_for_each_entry(kp, &smack_known_list, list) {
		if (kp->smk_cipso == NULL)
			continue;

		spin_lock_bh(&kp->smk_cipsolock);

		if (kp->smk_cipso->smk_level == level &&
		    memcmp(kp->smk_cipso->smk_catset, cp, SMK_LABELLEN) == 0)
			final = kp->smk_known;
	struct smack_known *skp = smk_find_entry(smack);

		spin_unlock_bh(&kp->smk_cipsolock);

		if (final != NULL)
			break;
	}
	rcu_read_unlock();

	return final;
}

/**
 * smack_to_cipso - find the CIPSO option to go with a Smack label
 * @smack: a pointer to the smack label in question
 * @cp: where to put the result
 *
 * Returns zero if a value is available, non-zero otherwise.
 */
int smack_to_cipso(const char *smack, struct smack_cipso *cp)
{
	struct smack_known *kp;
	int found = 0;

	rcu_read_lock();
	list_for_each_entry_rcu(kp, &smack_known_list, list) {
		if (kp->smk_known == smack ||
		    strcmp(kp->smk_known, smack) == 0) {
			found = 1;
			break;
		}
	}
	rcu_read_unlock();

	if (found == 0 || kp->smk_cipso == NULL)
		return -ENOENT;

	memcpy(cp, kp->smk_cipso, sizeof(struct smack_cipso));
	if (skp == NULL)
		return 0;
	return skp->smk_secid;
}
+83 −154

File changed.

Preview size limit exceeded, changes collapsed.

+761 −232

File changed.

Preview size limit exceeded, changes collapsed.