/*
  File: fs/xattr.c

  Extended attribute handling.

  Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
  Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
  Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 */
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/xattr.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/security.h>
#include <linux/evm.h>
#include <linux/syscalls.h>
#include <linux/module.h>
#include <linux/fsnotify.h>
#include <linux/audit.h>
#include <asm/uaccess.h>


/*
 * Check permissions for extended attribute access.  This is a bit complicated
 * because different namespaces have very different rules.
 */
static int
xattr_permission(struct inode *inode, const char *name, int mask)
{
        /*
         * We can never set or remove an extended attribute on a read-only
         * filesystem  or on an immutable / append-only inode.
         */
        if (mask & MAY_WRITE) {
                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                        return -EPERM;
        }

        /*
         * No restriction for security.* and system.* from the VFS.  Decision
         * on these is left to the underlying filesystem / security module.
         */
        if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
            !strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
                return 0;

        /*
         * The trusted.* namespace can only be accessed by privileged users.
         */
        if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
                if (!capable(CAP_SYS_ADMIN))
                        return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
                return 0;
        }

        /*
         * In the user.* namespace, only regular files and directories can have
         * extended attributes. For sticky directories, only the owner and
         * privileged users can write attributes.
         */
        if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
                if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
                        return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
                if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
                    (mask & MAY_WRITE) && !inode_owner_or_capable(inode))
                        return -EPERM;
        }

        return inode_permission(inode, mask);
}

/**
 *  __vfs_setxattr_noperm - perform setxattr operation without performing
 *  permission checks.
 *
 *  @dentry - object to perform setxattr on
 *  @name - xattr name to set
 *  @value - value to set @name to
 *  @size - size of @value
 *  @flags - flags to pass into filesystem operations
 *
 *  returns the result of the internal setxattr or setsecurity operations.
 *
 *  This function requires the caller to lock the inode's i_mutex before it
 *  is executed. It also assumes that the caller will make the appropriate
 *  permission checks.
 */
int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
                const void *value, size_t size, int flags)
{
        struct inode *inode = dentry->d_inode;
        int error = -EOPNOTSUPP;
        int issec = !strncmp(name, XATTR_SECURITY_PREFIX,
                                   XATTR_SECURITY_PREFIX_LEN);

        if (issec)
                inode->i_flags &= ~S_NOSEC;
        if (inode->i_op->setxattr) {
                error = inode->i_op->setxattr(dentry, name, value, size, flags);
                if (!error) {
                        fsnotify_xattr(dentry);
                        security_inode_post_setxattr(dentry, name, value,
                                                     size, flags);
                }
        } else if (issec) {
                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
                error = security_inode_setsecurity(inode, suffix, value,
                                                   size, flags);
                if (!error)
                        fsnotify_xattr(dentry);
        }

        return error;
}


int
vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
                size_t size, int flags)
{
        struct inode *inode = dentry->d_inode;
        int error;

        error = xattr_permission(inode, name, MAY_WRITE);
        if (error)
                return error;

        mutex_lock(&inode->i_mutex);
        error = security_inode_setxattr(dentry, name, value, size, flags);
        if (error)
                goto out;

        error = __vfs_setxattr_noperm(dentry, name, value, size, flags);

out:
        mutex_unlock(&inode->i_mutex);
        return error;
}
EXPORT_SYMBOL_GPL(vfs_setxattr);

ssize_t
xattr_getsecurity(struct inode *inode, const char *name, void *value,
                        size_t size)
{
        void *buffer = NULL;
        ssize_t len;

        if (!value || !size) {
                len = security_inode_getsecurity(inode, name, &buffer, false);
                goto out_noalloc;
        }

        len = security_inode_getsecurity(inode, name, &buffer, true);
        if (len < 0)
                return len;
        if (size < len) {
                len = -ERANGE;
                goto out;
        }
        memcpy(value, buffer, len);
out:
        security_release_secctx(buffer, len);
out_noalloc:
        return len;
}
EXPORT_SYMBOL_GPL(xattr_getsecurity);

/*
 * vfs_getxattr_alloc - allocate memory, if necessary, before calling getxattr
 *
 * Allocate memory, if not already allocated, or re-allocate correct size,
 * before retrieving the extended attribute.
 *
 * Returns the result of alloc, if failed, or the getxattr operation.
 */
ssize_t
vfs_getxattr_alloc(struct dentry *dentry, const char *name, char **xattr_value,
                   size_t xattr_size, gfp_t flags)
{
        struct inode *inode = dentry->d_inode;
        char *value = *xattr_value;
        int error;

        error = xattr_permission(inode, name, MAY_READ);
        if (error)
                return error;

        if (!inode->i_op->getxattr)
                return -EOPNOTSUPP;

        error = inode->i_op->getxattr(dentry, name, NULL, 0);
        if (error < 0)
                return error;

        if (!value || (error > xattr_size)) {
                value = krealloc(*xattr_value, error + 1, flags);
                if (!value)
                        return -ENOMEM;
                memset(value, 0, error + 1);
        }

        error = inode->i_op->getxattr(dentry, name, value, error);
        *xattr_value = value;
        return error;
}

/* Compare an extended attribute value with the given value */
int vfs_xattr_cmp(struct dentry *dentry, const char *xattr_name,
                  const char *value, size_t size, gfp_t flags)
{
        char *xattr_value = NULL;
        int rc;

        rc = vfs_getxattr_alloc(dentry, xattr_name, &xattr_value, 0, flags);
        if (rc < 0)
                return rc;

        if ((rc != size) || (memcmp(xattr_value, value, rc) != 0))
                rc = -EINVAL;
        else
                rc = 0;
        kfree(xattr_value);
        return rc;
}

ssize_t
vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
{
        struct inode *inode = dentry->d_inode;
        int error;

        error = xattr_permission(inode, name, MAY_READ);
        if (error)
                return error;

        error = security_inode_getxattr(dentry, name);
        if (error)
                return error;

        if (!strncmp(name, XATTR_SECURITY_PREFIX,
                                XATTR_SECURITY_PREFIX_LEN)) {
                const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
                int ret = xattr_getsecurity(inode, suffix, value, size);
                /*
                 * Only overwrite the return value if a security module
                 * is actually active.
                 */
                if (ret == -EOPNOTSUPP)
                        goto nolsm;
                return ret;
        }
nolsm:
        if (inode->i_op->getxattr)
                error = inode->i_op->getxattr(dentry, name, value, size);
        else
                error = -EOPNOTSUPP;

        return error;
}
EXPORT_SYMBOL_GPL(vfs_getxattr);

ssize_t
vfs_listxattr(struct dentry *d, char *list, size_t size)
{
        ssize_t error;

        error = security_inode_listxattr(d);
        if (error)
                return error;
        error = -EOPNOTSUPP;
        if (d->d_inode->i_op->listxattr) {
                error = d->d_inode->i_op->listxattr(d, list, size);
        } else {
                error = security_inode_listsecurity(d->d_inode, list, size);
                if (size && error > size)
                        error = -ERANGE;
        }
        return error;
}
EXPORT_SYMBOL_GPL(vfs_listxattr);

int
vfs_removexattr(struct dentry *dentry, const char *name)
{
        struct inode *inode = dentry->d_inode;
        int error;

        if (!inode->i_op->removexattr)
                return -EOPNOTSUPP;

        error = xattr_permission(inode, name, MAY_WRITE);
        if (error)
                return error;

        error = security_inode_removexattr(dentry, name);
        if (error)
                return error;

        mutex_lock(&inode->i_mutex);
        error = inode->i_op->removexattr(dentry, name);
        mutex_unlock(&inode->i_mutex);

        if (!error) {
                fsnotify_xattr(dentry);
                evm_inode_post_removexattr(dentry, name);
        }
        return error;
}
EXPORT_SYMBOL_GPL(vfs_removexattr);


/*
 * Extended attribute SET operations
 */
static long
setxattr(struct dentry *d, const char __user *name, const void __user *value,
         size_t size, int flags)
{
        int error;
        void *kvalue = NULL;
        char kname[XATTR_NAME_MAX + 1];

        if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
                return -EINVAL;

        error = strncpy_from_user(kname, name, sizeof(kname));
        if (error == 0 || error == sizeof(kname))
                error = -ERANGE;
        if (error < 0)
                return error;

        if (size) {
                if (size > XATTR_SIZE_MAX)
                        return -E2BIG;
                kvalue = memdup_user(value, size);
                if (IS_ERR(kvalue))
                        return PTR_ERR(kvalue);
        }

        error = vfs_setxattr(d, kname, kvalue, size, flags);
        kfree(kvalue);
        return error;
}

SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
                const char __user *, name, const void __user *, value,
                size_t, size, int, flags)
{
        struct path path;
        int error;

        error = user_path(pathname, &path);
        if (error)
                return error;
        error = mnt_want_write(path.mnt);
        if (!error) {
                error = setxattr(path.dentry, name, value, size, flags);
                mnt_drop_write(path.mnt);
        }
        path_put(&path);
        return error;
}

SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
                const char __user *, name, const void __user *, value,
                size_t, size, int, flags)
{
        struct path path;
        int error;

        error = user_lpath(pathname, &path);
        if (error)
                return error;
        error = mnt_want_write(path.mnt);
        if (!error) {
                error = setxattr(path.dentry, name, value, size, flags);
                mnt_drop_write(path.mnt);
        }
        path_put(&path);
        return error;
}

SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
                const void __user *,value, size_t, size, int, flags)
{
        struct file *f;
        struct dentry *dentry;
        int error = -EBADF;

        f = fget(fd);
        if (!f)
                return error;
        dentry = f->f_path.dentry;
        audit_inode(NULL, dentry);
        error = mnt_want_write_file(f);
        if (!error) {
                error = setxattr(dentry, name, value, size, flags);
                mnt_drop_write_file(f);
        }
        fput(f);
        return error;
}

/*
 * Extended attribute GET operations
 */
static ssize_t
getxattr(struct dentry *d, const char __user *name, void __user *value,
         size_t size)
{
        ssize_t error;
        void *kvalue = NULL;
        char kname[XATTR_NAME_MAX + 1];

        error = strncpy_from_user(kname, name, sizeof(kname));
        if (error == 0 || error == sizeof(kname))
                error = -ERANGE;
        if (error < 0)
                return error;

        if (size) {
                if (size > XATTR_SIZE_MAX)
                        size = XATTR_SIZE_MAX;
                kvalue = kzalloc(size, GFP_KERNEL);
                if (!kvalue)
                        return -ENOMEM;
        }

        error = vfs_getxattr(d, kname, kvalue, size);
        if (error > 0) {
                if (size && copy_to_user(value, kvalue, error))
                        error = -EFAULT;
        } else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
                /* The file system tried to returned a value bigger
                   than XATTR_SIZE_MAX bytes. Not possible. */
                error = -E2BIG;
        }
        kfree(kvalue);
        return error;
}

SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
                const char __user *, name, void __user *, value, size_t, size)
{
        struct path path;
        ssize_t error;

        error = user_path(pathname, &path);
        if (error)
                return error;
        error = getxattr(path.dentry, name, value, size);
        path_put(&path);
        return error;
}

SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
                const char __user *, name, void __user *, value, size_t, size)
{
        struct path path;
        ssize_t error;

        error = user_lpath(pathname, &path);
        if (error)
                return error;
        error = getxattr(path.dentry, name, value, size);
        path_put(&path);
        return error;
}

SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
                void __user *, value, size_t, size)
{
        struct file *f;
        ssize_t error = -EBADF;

        f = fget(fd);
        if (!f)
                return error;
        audit_inode(NULL, f->f_path.dentry);
        error = getxattr(f->f_path.dentry, name, value, size);
        fput(f);
        return error;
}

/*
 * Extended attribute LIST operations
 */
static ssize_t
listxattr(struct dentry *d, char __user *list, size_t size)
{
        ssize_t error;
        char *klist = NULL;

        if (size) {
                if (size > XATTR_LIST_MAX)
                        size = XATTR_LIST_MAX;
                klist = kmalloc(size, GFP_KERNEL);
                if (!klist)
                        return -ENOMEM;
        }

        error = vfs_listxattr(d, klist, size);
        if (error > 0) {
                if (size && copy_to_user(list, klist, error))
                        error = -EFAULT;
        } else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
                /* The file system tried to returned a list bigger
                   than XATTR_LIST_MAX bytes. Not possible. */
                error = -E2BIG;
        }
        kfree(klist);
        return error;
}

SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
                size_t, size)
{
        struct path path;
        ssize_t error;

        error = user_path(pathname, &path);
        if (error)
                return error;
        error = listxattr(path.dentry, list, size);
        path_put(&path);
        return error;
}

SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
                size_t, size)
{
        struct path path;
        ssize_t error;

        error = user_lpath(pathname, &path);
        if (error)
                return error;
        error = listxattr(path.dentry, list, size);
        path_put(&path);
        return error;
}

SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
{
        struct file *f;
        ssize_t error = -EBADF;

        f = fget(fd);
        if (!f)
                return error;
        audit_inode(NULL, f->f_path.dentry);
        error = listxattr(f->f_path.dentry, list, size);
        fput(f);
        return error;
}

/*
 * Extended attribute REMOVE operations
 */
static long
removexattr(struct dentry *d, const char __user *name)
{
        int error;
        char kname[XATTR_NAME_MAX + 1];

        error = strncpy_from_user(kname, name, sizeof(kname));
        if (error == 0 || error == sizeof(kname))
                error = -ERANGE;
        if (error < 0)
                return error;

        return vfs_removexattr(d, kname);
}

SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
                const char __user *, name)
{
        struct path path;
        int error;

        error = user_path(pathname, &path);
        if (error)
                return error;
        error = mnt_want_write(path.mnt);
        if (!error) {
                error = removexattr(path.dentry, name);
                mnt_drop_write(path.mnt);
        }
        path_put(&path);
        return error;
}

SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
                const char __user *, name)
{
        struct path path;
        int error;

        error = user_lpath(pathname, &path);
        if (error)
                return error;
        error = mnt_want_write(path.mnt);
        if (!error) {
                error = removexattr(path.dentry, name);
                mnt_drop_write(path.mnt);
        }
        path_put(&path);
        return error;
}

SYSCALL_DEFINE2(fremovexattr, int, fd, const char __user *, name)
{
        struct file *f;
        struct dentry *dentry;
        int error = -EBADF;

        f = fget(fd);
        if (!f)
                return error;
        dentry = f->f_path.dentry;
        audit_inode(NULL, dentry);
        error = mnt_want_write_file(f);
        if (!error) {
                error = removexattr(dentry, name);
                mnt_drop_write_file(f);
        }
        fput(f);
        return error;
}


static const char *
strcmp_prefix(const char *a, const char *a_prefix)
{
        while (*a_prefix && *a == *a_prefix) {
                a++;
                a_prefix++;
        }
        return *a_prefix ? NULL : a;
}

/*
 * In order to implement different sets of xattr operations for each xattr
 * prefix with the generic xattr API, a filesystem should create a
 * null-terminated array of struct xattr_handler (one for each prefix) and
 * hang a pointer to it off of the s_xattr field of the superblock.
 *
 * The generic_fooxattr() functions will use this list to dispatch xattr
 * operations to the correct xattr_handler.
 */
#define for_each_xattr_handler(handlers, handler)               \
                for ((handler) = *(handlers)++;                 \
                        (handler) != NULL;                      \
                        (handler) = *(handlers)++)

/*
 * Find the xattr_handler with the matching prefix.
 */
static const struct xattr_handler *
xattr_resolve_name(const struct xattr_handler **handlers, const char **name)
{
        const struct xattr_handler *handler;

        if (!*name)
                return NULL;

        for_each_xattr_handler(handlers, handler) {
                const char *n = strcmp_prefix(*name, handler->prefix);
                if (n) {
                        *name = n;
                        break;
                }
        }
        return handler;
}

/*
 * Find the handler for the prefix and dispatch its get() operation.
 */
ssize_t
generic_getxattr(struct dentry *dentry, const char *name, void *buffer, size_t size)
{
        const struct xattr_handler *handler;

        handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
        if (!handler)
                return -EOPNOTSUPP;
        return handler->get(dentry, name, buffer, size, handler->flags);
}

/*
 * Combine the results of the list() operation from every xattr_handler in the
 * list.
 */
ssize_t
generic_listxattr(struct dentry *dentry, char *buffer, size_t buffer_size)
{
        const struct xattr_handler *handler, **handlers = dentry->d_sb->s_xattr;
        unsigned int size = 0;

        if (!buffer) {
                for_each_xattr_handler(handlers, handler) {
                        size += handler->list(dentry, NULL, 0, NULL, 0,
                                              handler->flags);
                }
        } else {
                char *buf = buffer;

                for_each_xattr_handler(handlers, handler) {
                        size = handler->list(dentry, buf, buffer_size,
                                             NULL, 0, handler->flags);
                        if (size > buffer_size)
                                return -ERANGE;
                        buf += size;
                        buffer_size -= size;
                }
                size = buf - buffer;
        }
        return size;
}

/*
 * Find the handler for the prefix and dispatch its set() operation.
 */
int
generic_setxattr(struct dentry *dentry, const char *name, const void *value, size_t size, int flags)
{
        const struct xattr_handler *handler;

        if (size == 0)
                value = "";  /* empty EA, do not remove */
        handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
        if (!handler)
                return -EOPNOTSUPP;
        return handler->set(dentry, name, value, size, flags, handler->flags);
}

/*
 * Find the handler for the prefix and dispatch its set() operation to remove
 * any associated extended attribute.
 */
int
generic_removexattr(struct dentry *dentry, const char *name)
{
        const struct xattr_handler *handler;

        handler = xattr_resolve_name(dentry->d_sb->s_xattr, &name);
        if (!handler)
                return -EOPNOTSUPP;
        return handler->set(dentry, name, NULL, 0,
                            XATTR_REPLACE, handler->flags);
}

EXPORT_SYMBOL(generic_getxattr);
EXPORT_SYMBOL(generic_listxattr);
EXPORT_SYMBOL(generic_setxattr);
EXPORT_SYMBOL(generic_removexattr);