[TOMOYO #8 (2.6.25-mm1) 3/7] Memory and pathname management functions.

[Toshiharu Harada]

TOMOYO Linux performs pathname based access control.
To remove factors that make pathname based access control difficult
(e.g. symbolic links, "..", "//" etc.), TOMOYO Linux derives realpath
of requested pathname from "struct dentry" and "struct vfsmount".

The maximum length of string data is limited to 4000 including trailing '\0'.
Since TOMOYO Linux uses '\ooo' style representation for non ASCII printable
characters, may be TOMOYO Linux should be able to support 16336 (which means
(NAME_MAX * (PATH_MAX / (NAME_MAX + 1)) * 4 + (PATH_MAX / (NAME_MAX + 1)))
including trailing '\0'), but I think 4000 is enough for practical use.

Signed-off-by: Kentaro Takeda <takedakn@xxxxxxxxxxxxx>
Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Toshiharu Harada <haradats@xxxxxxxxxxxxx>
---
 security/tomoyo/realpath.c |  655 +++++++++++++++++++++++++++++++++++++++++++++
 security/tomoyo/realpath.h |   62 ++++
 2 files changed, 717 insertions(+)

--- /dev/null
+++ mm/security/tomoyo/realpath.h
@@ -0,0 +1,62 @@
+/*
+ * security/tomoyo/realpath.h
+ *
+ * Get the canonicalized absolute pathnames. The basis for TOMOYO.
+ *
+ * Copyright (C) 2005-2008  NTT DATA CORPORATION
+ *
+ * Version: 2.2.0-pre   2008/04/30
+ *
+ */
+
+#ifndef _LINUX_REALPATH_H
+#define _LINUX_REALPATH_H
+
+struct dentry;
+struct vfsmount;
+struct condition_list;
+struct path_info;
+
+/* Returns realpath(3) of the given pathname but ignores chroot'ed root. */
+int tmy_realpath_from_dentry2(struct dentry *dentry, struct vfsmount *mnt,
+			      char *newname, int newname_len);
+
+/*
+ * Returns realpath(3) of the given pathname but ignores chroot'ed root.
+ * These functions use tmy_alloc(), so caller must tmy_free()
+ * if these functions didn't return NULL.
+ */
+char *tmy_realpath(const char *pathname);
+/* Same with tmy_realpath() except that it doesn't follow the final symlink. */
+char *tmy_realpath_nofollow(const char *pathname);
+/* Same with tmy_realpath() except that the pathname is already solved. */
+char *tmy_realpath_from_dentry(struct dentry *dentry, struct vfsmount *mnt);
+
+/*
+ * Allocate memory for ACL entry.
+ * The RAM is chunked, so NEVER try to kfree() the returned pointer.
+ */
+void *tmy_alloc_element(const unsigned int size);
+
+/* Get used RAM size for tmy_alloc_elements(). */
+unsigned int tmy_get_memory_used_for_elements(void);
+
+/*
+ * Keep the given name on the RAM.
+ * The RAM is shared, so NEVER try to modify or kfree() the returned name.
+ */
+const struct path_info *tmy_save_name(const char *name);
+
+/* Get used RAM size for tmy_save_name(). */
+unsigned int tmy_get_memory_used_for_save_name(void);
+
+/* Allocate memory for temporary use (e.g. permission checks). */
+void *tmy_alloc(const size_t size);
+
+/* Get used RAM size for tmy_alloc(). */
+unsigned int tmy_get_memory_used_for_dynamic(void);
+
+/* Free memory allocated by tmy_alloc(). */
+void tmy_free(const void *p);
+
+#endif
--- /dev/null
+++ mm/security/tomoyo/realpath.c
@@ -0,0 +1,655 @@
+/*
+ * security/tomoyo/realpath.c
+ *
+ * Get the canonicalized absolute pathnames. The basis for TOMOYO.
+ *
+ * Copyright (C) 2005-2008  NTT DATA CORPORATION
+ *
+ * Version: 2.2.0-pre   2008/04/30
+ *
+ */
+
+#include <linux/types.h>
+#include <linux/mount.h>
+#include <linux/magic.h>
+#include <linux/sysctl.h>
+#include "common.h"
+#include "realpath.h"
+
+/**
+ * get_absolute_path - Get the path of a dentry but ignores chroot'ed root.
+ *
+ * @dentry: Pointer to "struct dentry".
+ * @vfsmnt: Pointer to "struct vfsmount".
+ * @buffer: Pointer to buffer to return value in.
+ * @buflen: Sizeof @buffer.
+ *
+ * Returns 0 on success, -ENOMEM otherwise.
+ *
+ * Caller holds the dcache_lock and vfsmount_lock.
+ * Based on __d_path() in fs/dcache.c
+ *
+ * If dentry is a directory, trailing '/' is appended.
+ * Characters out of 0x20 < c < 0x7F range are converted to
+ * \ooo style octal string.
+ * Character \ is converted to \\ string.
+ */
+static int get_absolute_path(struct dentry *dentry, struct vfsmount *vfsmnt,
+			     char *buffer, int buflen)
+{
+	/***** CRITICAL SECTION START *****/
+	char *start = buffer;
+	char *end = buffer + buflen;
+	bool is_dir = (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode));
+
+	if (buflen < 256)
+		goto out;
+
+	*--end = '\0';
+	buflen--;
+
+	for (;;) {
+		struct dentry *parent;
+
+		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+			/* Global root? */
+			if (vfsmnt->mnt_parent == vfsmnt)
+				break;
+			dentry = vfsmnt->mnt_mountpoint;
+			vfsmnt = vfsmnt->mnt_parent;
+			continue;
+		}
+		if (is_dir) {
+			is_dir = false;
+			*--end = '/';
+			buflen--;
+		}
+		parent = dentry->d_parent;
+		{
+			const char *sp = dentry->d_name.name;
+			const char *cp = sp + dentry->d_name.len - 1;
+			unsigned char c;
+
+			/*
+			 * Exception: Use /proc/self/ rather than
+			 * /proc/\$/ for current process.
+			 */
+			if (IS_ROOT(parent) && *sp > '0' && *sp <= '9' &&
+			    parent->d_sb &&
+			    parent->d_sb->s_magic == PROC_SUPER_MAGIC) {
+				char *ep;
+				const pid_t pid
+					= (pid_t) simple_strtoul(sp, &ep, 10);
+				if (!*ep && pid == current->tgid) {
+					sp = "self";
+					cp = sp + 3;
+				}
+			}
+
+			while (sp <= cp) {
+				c = *(unsigned char *) cp;
+				if (c == '\\') {
+					buflen -= 2;
+					if (buflen < 0)
+						goto out;
+					*--end = '\\';
+					*--end = '\\';
+				} else if (c > ' ' && c < 127) {
+					if (--buflen < 0)
+						goto out;
+					*--end = (char) c;
+				} else {
+					buflen -= 4;
+					if (buflen < 0)
+						goto out;
+					*--end = (c & 7) + '0';
+					*--end = ((c >> 3) & 7) + '0';
+					*--end = (c >> 6) + '0';
+					*--end = '\\';
+				}
+				cp--;
+			}
+			if (--buflen < 0)
+				goto out;
+			*--end = '/';
+		}
+		dentry = parent;
+	}
+	if (*end == '/') {
+		buflen++;
+		end++;
+	}
+	{
+		const char *sp = dentry->d_name.name;
+		const char *cp = sp + dentry->d_name.len - 1;
+		unsigned char c;
+		while (sp <= cp) {
+			c = *(unsigned char *) cp;
+			if (c == '\\') {
+				buflen -= 2;
+				if (buflen < 0)
+					goto out;
+				*--end = '\\';
+				*--end = '\\';
+			} else if (c > ' ' && c < 127) {
+				if (--buflen < 0)
+					goto out;
+				*--end = (char) c;
+			} else {
+				buflen -= 4;
+				if (buflen < 0)
+					goto out;
+				*--end = (c & 7) + '0';
+				*--end = ((c >> 3) & 7) + '0';
+				*--end = (c >> 6) + '0';
+				*--end = '\\';
+			}
+			cp--;
+		}
+	}
+	/* Move the pathname to the top of the buffer. */
+	memmove(start, end, strlen(end) + 1);
+	return 0;
+out:
+	return -ENOMEM;
+	/***** CRITICAL SECTION END *****/
+}
+
+/**
+ * tmy_realpath_from_dentry2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
+ *
+ * @dentry:      Pointer to "struct dentry".
+ * @mnt:         Pointer to "struct vfsmount".
+ * @newname:     Pointer to buffer to return value in.
+ * @newname_len: Size of @newname.
+ *
+ * Returns 0 on success, negative value otherwise.
+ */
+int tmy_realpath_from_dentry2(struct dentry *dentry, struct vfsmount *mnt,
+			      char *newname, int newname_len)
+{
+	int error;
+	struct dentry *d_dentry;
+	struct vfsmount *d_mnt;
+	if (!dentry || !mnt || !newname || newname_len <= 0)
+		return -EINVAL;
+	d_dentry = dget(dentry);
+	d_mnt = mntget(mnt);
+	/***** CRITICAL SECTION START *****/
+	spin_lock(&dcache_lock);
+	spin_lock(&vfsmount_lock);
+	error = get_absolute_path(d_dentry, d_mnt, newname, newname_len);
+	spin_unlock(&vfsmount_lock);
+	spin_unlock(&dcache_lock);
+	/***** CRITICAL SECTION END *****/
+	dput(d_dentry);
+	mntput(d_mnt);
+	if (error)
+		printk(KERN_WARNING "tmy_realpath: Pathname too long.\n");
+	return error;
+}
+
+/**
+ * tmy_realpath_from_dentry - Returns realpath(3) of the given pathname but ignores chroot'ed root.
+ *
+ * @dentry: Pointer to "struct dentry".
+ * @mnt:    Pointer to "struct vfsmount".
+ *
+ * Returns the realpath of the given @dentry and @mnt on success,
+ * NULL otherwise.
+ *
+ * These functions use tmy_alloc(), so caller must tmy_free()
+ * if these functions didn't return NULL.
+ */
+char *tmy_realpath_from_dentry(struct dentry *dentry, struct vfsmount *mnt)
+{
+	char *buf = tmy_alloc(sizeof(struct tmy_page_buffer));
+	if (buf && tmy_realpath_from_dentry2(dentry, mnt, buf,
+					     TMY_MAX_PATHNAME_LEN - 1) == 0)
+		return buf;
+	tmy_free(buf);
+	return NULL;
+}
+
+/**
+ * tmy_realpath - Get realpath of a pathname.
+ *
+ * @pathname: The pathname to solve.
+ *
+ * Returns the realpath of @pathname on success, NULL otherwise.
+ */
+char *tmy_realpath(const char *pathname)
+{
+	struct nameidata nd;
+	if (pathname && path_lookup(pathname, LOOKUP_FOLLOW, &nd) == 0) {
+		char *buf = tmy_realpath_from_dentry(nd.path.dentry,
+						     nd.path.mnt);
+		path_put(&nd.path);
+		return buf;
+	}
+	return NULL;
+}
+
+/**
+ * tmy_realpath_nofollow - Get realpath of a pathname.
+ *
+ * @pathname: The pathname to solve.
+ *
+ * Returns the realpath of @pathname on success, NULL otherwise.
+ */
+char *tmy_realpath_nofollow(const char *pathname)
+{
+	struct nameidata nd;
+	if (pathname && path_lookup(pathname, 0, &nd) == 0) {
+		char *buf = tmy_realpath_from_dentry(nd.path.dentry,
+						     nd.path.mnt);
+		path_put(&nd.path);
+		return buf;
+	}
+	return NULL;
+}
+
+/**
+ * round_up - Round up an integer so that the returned pointers are appropriately aligned.
+ *
+ * @size: Size in bytes.
+ *
+ * Returns rounded value of @size.
+ *
+ * FIXME: Are there more requirements that is needed for assigning value
+ * atomically?
+ */
+static inline unsigned int round_up(const unsigned int size)
+{
+	if (sizeof(void *) >= sizeof(long))
+		return ((size + sizeof(void *) - 1)
+			/ sizeof(void *)) * sizeof(void *);
+	else
+		return ((size + sizeof(long) - 1)
+			/ sizeof(long)) * sizeof(long);
+}
+
+static unsigned int allocated_memory_for_elements;
+
+/**
+ * tmy_get_memory_used_for_elements - Get memory used for keeping ACL structures.
+ *
+ * Returns memory used for keeping ACL structures.
+ */
+unsigned int tmy_get_memory_used_for_elements(void)
+{
+	return allocated_memory_for_elements;
+}
+
+/**
+ * tmy_alloc_element - Allocate permanent memory for structures.
+ *
+ * @size: Size in bytes.
+ *
+ * Returns pointer to allocated memory on success, NULL otherwise.
+ *
+ * The RAM is chunked, so NEVER try to kfree() the returned pointer.
+ */
+void *tmy_alloc_element(const unsigned int size)
+{
+	static DEFINE_MUTEX(lock);
+	static char *buf;
+	static unsigned int buf_used_len = PAGE_SIZE;
+	char *ptr = NULL;
+	const unsigned int word_aligned_size = round_up(size);
+	if (word_aligned_size > PAGE_SIZE)
+		return NULL;
+	mutex_lock(&lock);
+	if (buf_used_len + word_aligned_size > PAGE_SIZE) {
+		ptr = kzalloc(PAGE_SIZE, GFP_KERNEL);
+		if (!ptr) {
+			printk(KERN_WARNING "ERROR: Out of memory "
+			       "for tmy_alloc_element().\n");
+			if (!sbin_init_started)
+				panic("MAC Initialization failed.\n");
+		} else {
+			buf = ptr;
+			allocated_memory_for_elements += PAGE_SIZE;
+			buf_used_len = word_aligned_size;
+			ptr = buf;
+		}
+	} else if (word_aligned_size) {
+		int i;
+		ptr = buf + buf_used_len;
+		buf_used_len += word_aligned_size;
+		for (i = 0; i < word_aligned_size; i++) {
+			if (!ptr[i])
+				continue;
+			printk(KERN_ERR "WARNING: Reserved memory was tainted! "
+			       "The system might go wrong.\n");
+			ptr[i] = '\0';
+		}
+	}
+	mutex_unlock(&lock);
+	return ptr;
+}
+
+static unsigned int allocated_memory_for_savename;
+
+/**
+ * tmy_get_memory_used_for_save_name - Get memory used for keeping string data.
+ *
+ * Returns memory used for keeping string data.
+ */
+unsigned int tmy_get_memory_used_for_save_name(void)
+{
+	return allocated_memory_for_savename;
+}
+
+#define MAX_HASH 256
+
+/* Structure for string data. */
+struct name_entry {
+	struct list1_head list;
+	struct path_info entry;
+};
+
+/* Structure for available memory region. */
+struct free_memory_block_list {
+	struct list_head list;
+	char *ptr;             /* Pointer to a free area. */
+	int len;               /* Length of the area.     */
+};
+
+/* The list for "struct name_entry". */
+static struct list1_head name_list[MAX_HASH];
+
+/**
+ * tmy_save_name - Allocate permanent memory for string data.
+ *
+ * @name: The string to store into the permernent memory.
+ *
+ * Returns pointer to "struct path_info" on success, NULL otherwise.
+ *
+ * The RAM is shared, so NEVER try to modify or kfree() the returned name.
+ */
+const struct path_info *tmy_save_name(const char *name)
+{
+	static LIST_HEAD(fmb_list);
+	static DEFINE_MUTEX(lock);
+	struct name_entry *ptr;
+	unsigned int hash;
+	struct free_memory_block_list *fmb;
+	int len;
+	char *cp;
+	if (!name)
+		return NULL;
+	len = strlen(name) + 1;
+	if (len > TMY_MAX_PATHNAME_LEN) {
+		printk(KERN_WARNING "ERROR: Name too long "
+		       "for tmy_save_name().\n");
+		return NULL;
+	}
+	hash = full_name_hash((const unsigned char *) name, len - 1);
+	mutex_lock(&lock);
+	list1_for_each_entry(ptr, &name_list[hash % MAX_HASH], list) {
+		if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
+			goto out;
+	}
+	list_for_each_entry(fmb, &fmb_list, list) {
+		if (len <= fmb->len)
+			goto ready;
+	}
+	cp = kzalloc(PAGE_SIZE, GFP_KERNEL);
+	fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
+	if (!cp || !fmb) {
+		kfree(cp);
+		kfree(fmb);
+		printk(KERN_WARNING "ERROR: Out of memory "
+		       "for tmy_save_name().\n");
+		if (!sbin_init_started)
+			panic("MAC Initialization failed.\n");
+		ptr = NULL;
+		goto out;
+	}
+	allocated_memory_for_savename += PAGE_SIZE;
+	list_add(&fmb->list, &fmb_list);
+	fmb->ptr = cp;
+	fmb->len = PAGE_SIZE;
+ready:
+	ptr = tmy_alloc_element(sizeof(*ptr));
+	if (!ptr)
+		goto out;
+	ptr->entry.name = fmb->ptr;
+	memmove(fmb->ptr, name, len);
+	tmy_fill_path_info(&ptr->entry);
+	fmb->ptr += len;
+	fmb->len -= len;
+	list1_add_tail_mb(&ptr->list, &name_list[hash % MAX_HASH]);
+	if (fmb->len == 0) {
+		list_del(&fmb->list);
+		kfree(fmb);
+	}
+out:
+	mutex_unlock(&lock);
+	return ptr ? &ptr->entry : NULL;
+}
+
+/* Structure for temporarily allocated memory. */
+struct cache_entry {
+	struct list_head list;
+	void *ptr;
+	int size;
+};
+
+static struct kmem_cache *tmy_cachep;
+
+/**
+ * tmy_realpath_init - Initialize realpath related code.
+ *
+ * Returns 0.
+ */
+static int __init tmy_realpath_init(void)
+{
+	int i;
+	if (TMY_MAX_PATHNAME_LEN > PAGE_SIZE)
+		panic("Bad size.");
+	tmy_cachep = kmem_cache_create("tmy_cache", sizeof(struct cache_entry),
+				       0, 0, NULL);
+	if (!tmy_cachep)
+		panic("Can't create cache.\n");
+	for (i = 0; i < MAX_HASH; i++)
+		INIT_LIST1_HEAD(&name_list[i]);
+	INIT_LIST1_HEAD(&KERNEL_DOMAIN.acl_info_list);
+	KERNEL_DOMAIN.domainname = tmy_save_name(ROOT_NAME);
+	list1_add_tail_mb(&KERNEL_DOMAIN.list, &domain_list);
+	if (tmy_find_domain(ROOT_NAME) != &KERNEL_DOMAIN)
+		panic("Can't register KERNEL_DOMAIN");
+	return 0;
+}
+
+security_initcall(tmy_realpath_init);
+
+/* The list for "struct cache_entry". */
+static LIST_HEAD(cache_list);
+
+static DEFINE_SPINLOCK(cache_list_lock);
+
+static unsigned int dynamic_memory_size;
+
+/**
+ * tmy_get_memory_used_for_dynamic - Get memory used for temporal purpose.
+ *
+ * Returns memory used for temporal purpose.
+ */
+unsigned int tmy_get_memory_used_for_dynamic(void)
+{
+	return dynamic_memory_size;
+}
+
+/**
+ * tmy_alloc - Allocate memory for temporal purpose.
+ *
+ * @size: Size in bytes.
+ *
+ * Returns pointer to allocated memory on success, NULL otherwise.
+ */
+void *tmy_alloc(const size_t size)
+{
+	struct cache_entry *new_entry;
+	void *ret = kzalloc(size, GFP_KERNEL);
+	if (!ret)
+		goto out;
+	new_entry = kmem_cache_alloc(tmy_cachep, GFP_KERNEL);
+	if (!new_entry) {
+		kfree(ret);
+		ret = NULL;
+		goto out;
+	}
+	INIT_LIST_HEAD(&new_entry->list);
+	new_entry->ptr = ret;
+	new_entry->size = ksize(ret);
+	/***** CRITICAL SECTION START *****/
+	spin_lock(&cache_list_lock);
+	list_add_tail(&new_entry->list, &cache_list);
+	dynamic_memory_size += new_entry->size;
+	spin_unlock(&cache_list_lock);
+	/***** CRITICAL SECTION END *****/
+out:
+	return ret;
+}
+
+/**
+ * tmy_free - Release memory allocated by tmy_alloc().
+ *
+ * @p: Pointer returned by tmy_alloc(). May be NULL.
+ *
+ * Returns nothing.
+ */
+void tmy_free(const void *p)
+{
+	struct list_head *v;
+	struct cache_entry *entry = NULL;
+	if (!p)
+		return;
+	/***** CRITICAL SECTION START *****/
+	spin_lock(&cache_list_lock);
+	list_for_each(v, &cache_list) {
+		entry = list_entry(v, struct cache_entry, list);
+		if (entry->ptr != p) {
+			entry = NULL;
+			continue;
+		}
+		list_del(&entry->list);
+		dynamic_memory_size -= entry->size;
+		break;
+	}
+	spin_unlock(&cache_list_lock);
+	/***** CRITICAL SECTION END *****/
+	if (entry) {
+		kfree(p);
+		kmem_cache_free(tmy_cachep, entry);
+	} else {
+		printk(KERN_WARNING "BUG: tmy_free() with invalid pointer.\n");
+	}
+}
+
+static int tmy_print_ascii(const char *sp, const char *cp,
+			   int *buflen0, char **end0)
+{
+	int buflen = *buflen0;
+	char *end = *end0;
+
+	while (sp <= cp) {
+		unsigned char c;
+
+		c = *(unsigned char *) cp;
+		if (c == '\\') {
+			buflen -= 2;
+			if (buflen < 0)
+				goto out;
+			*--end = '\\';
+			*--end = '\\';
+		} else if (c > ' ' && c < 127) {
+			if (--buflen < 0)
+				goto out;
+			*--end = (char) c;
+		} else {
+			buflen -= 4;
+			if (buflen < 0)
+				goto out;
+			*--end = (c & 7) + '0';
+			*--end = ((c >> 3) & 7) + '0';
+			*--end = (c >> 6) + '0';
+			*--end = '\\';
+		}
+		cp--;
+	}
+
+	*buflen0 = buflen;
+	*end0 = end;
+
+	return 0;
+out:
+	return -ENOMEM;
+}
+
+
+/* tmy_get_absolute_path() for "struct ctl_table". */
+static int tmy_sysctl_path(struct ctl_table *table, char *buffer, int buflen)
+{
+	char *end = buffer + buflen;
+
+	if (buflen < 256)
+		goto out;
+
+	*--end = '\0';
+	buflen--;
+
+	buflen -= 9; /* for "/proc/sys" prefix */
+
+	while (table) {
+		char buf[32];
+		const char *sp = table->procname;
+		const char *cp;
+
+		if (!sp) {
+			memset(buf, 0, sizeof(buf));
+			snprintf(buf, sizeof(buf) - 1, "=%d=", table->ctl_name);
+			sp = buf;
+		}
+		cp = strchr(sp, '\0') - 1;
+
+		if (tmy_print_ascii(sp, cp, &buflen, &end))
+			goto out;
+
+		if (--buflen < 0)
+			goto out;
+
+		*--end = '/';
+		table = table->parent;
+	}
+
+	/* Move the pathname to the top of the buffer. */
+	memmove(buffer, "/proc/sys", 9);
+	memmove(buffer + 9, end, strlen(end) + 1);
+	return 0;
+out: ;
+	return -ENOMEM;
+}
+
+/**
+ * sysctlpath_from_table - return the realpath of a ctl_table.
+ * @table: pointer to "struct ctl_table".
+ *
+ * Returns realpath(3) of the @table on success.
+ * Returns NULL on failure.
+ *
+ * This function uses tmy_alloc(), so caller must call tmy_free()
+ * if this function didn't return NULL.
+ */
+char *sysctlpath_from_table(struct ctl_table *table)
+{
+	char *buf = tmy_alloc(TMY_MAX_PATHNAME_LEN);
+
+	if (buf && tmy_sysctl_path(table, buf, TMY_MAX_PATHNAME_LEN - 1) == 0)
+		return buf;
+
+	tmy_free(buf);
+	return NULL;
+}

--

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