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bb4354538e
The entries in xattr handler table should be immutable (ie const) like other operation tables. Later patches convert common filesystems. Uncoverted filesystems will still work, but will generate a compiler warning. Signed-off-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
692 lines
16 KiB
C
692 lines
16 KiB
C
/*
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File: fs/xattr.c
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Extended attribute handling.
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Copyright (C) 2001 by Andreas Gruenbacher <a.gruenbacher@computer.org>
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Copyright (C) 2001 SGI - Silicon Graphics, Inc <linux-xfs@oss.sgi.com>
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Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
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*/
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#include <linux/fs.h>
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#include <linux/slab.h>
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#include <linux/file.h>
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#include <linux/xattr.h>
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#include <linux/mount.h>
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#include <linux/namei.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/module.h>
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#include <linux/fsnotify.h>
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#include <linux/audit.h>
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#include <asm/uaccess.h>
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/*
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* Check permissions for extended attribute access. This is a bit complicated
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* because different namespaces have very different rules.
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*/
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static int
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xattr_permission(struct inode *inode, const char *name, int mask)
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{
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/*
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* We can never set or remove an extended attribute on a read-only
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* filesystem or on an immutable / append-only inode.
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*/
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if (mask & MAY_WRITE) {
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if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
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return -EPERM;
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}
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/*
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* No restriction for security.* and system.* from the VFS. Decision
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* on these is left to the underlying filesystem / security module.
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*/
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if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN) ||
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!strncmp(name, XATTR_SYSTEM_PREFIX, XATTR_SYSTEM_PREFIX_LEN))
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return 0;
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/*
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* The trusted.* namespace can only be accessed by a privileged user.
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*/
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if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN))
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return (capable(CAP_SYS_ADMIN) ? 0 : -EPERM);
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/* In user.* namespace, only regular files and directories can have
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* extended attributes. For sticky directories, only the owner and
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* privileged user can write attributes.
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*/
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if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
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if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
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return -EPERM;
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if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
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(mask & MAY_WRITE) && !is_owner_or_cap(inode))
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return -EPERM;
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}
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return inode_permission(inode, mask);
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}
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/**
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* __vfs_setxattr_noperm - perform setxattr operation without performing
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* permission checks.
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*
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* @dentry - object to perform setxattr on
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* @name - xattr name to set
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* @value - value to set @name to
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* @size - size of @value
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* @flags - flags to pass into filesystem operations
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*
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* returns the result of the internal setxattr or setsecurity operations.
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*
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* This function requires the caller to lock the inode's i_mutex before it
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* is executed. It also assumes that the caller will make the appropriate
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* permission checks.
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*/
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int __vfs_setxattr_noperm(struct dentry *dentry, const char *name,
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const void *value, size_t size, int flags)
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{
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struct inode *inode = dentry->d_inode;
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int error = -EOPNOTSUPP;
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if (inode->i_op->setxattr) {
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error = inode->i_op->setxattr(dentry, name, value, size, flags);
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if (!error) {
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fsnotify_xattr(dentry);
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security_inode_post_setxattr(dentry, name, value,
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size, flags);
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}
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} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
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XATTR_SECURITY_PREFIX_LEN)) {
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const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
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error = security_inode_setsecurity(inode, suffix, value,
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size, flags);
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if (!error)
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fsnotify_xattr(dentry);
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}
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return error;
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}
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int
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vfs_setxattr(struct dentry *dentry, const char *name, const void *value,
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size_t size, int flags)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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error = xattr_permission(inode, name, MAY_WRITE);
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if (error)
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return error;
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mutex_lock(&inode->i_mutex);
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error = security_inode_setxattr(dentry, name, value, size, flags);
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if (error)
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goto out;
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error = __vfs_setxattr_noperm(dentry, name, value, size, flags);
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out:
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mutex_unlock(&inode->i_mutex);
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_setxattr);
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ssize_t
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xattr_getsecurity(struct inode *inode, const char *name, void *value,
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size_t size)
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{
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void *buffer = NULL;
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ssize_t len;
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if (!value || !size) {
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len = security_inode_getsecurity(inode, name, &buffer, false);
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goto out_noalloc;
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}
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len = security_inode_getsecurity(inode, name, &buffer, true);
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if (len < 0)
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return len;
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if (size < len) {
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len = -ERANGE;
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goto out;
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}
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memcpy(value, buffer, len);
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out:
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security_release_secctx(buffer, len);
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out_noalloc:
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return len;
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}
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EXPORT_SYMBOL_GPL(xattr_getsecurity);
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ssize_t
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vfs_getxattr(struct dentry *dentry, const char *name, void *value, size_t size)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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error = xattr_permission(inode, name, MAY_READ);
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if (error)
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return error;
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error = security_inode_getxattr(dentry, name);
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if (error)
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return error;
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if (!strncmp(name, XATTR_SECURITY_PREFIX,
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XATTR_SECURITY_PREFIX_LEN)) {
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const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
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int ret = xattr_getsecurity(inode, suffix, value, size);
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/*
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* Only overwrite the return value if a security module
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* is actually active.
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*/
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if (ret == -EOPNOTSUPP)
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goto nolsm;
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return ret;
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}
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nolsm:
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if (inode->i_op->getxattr)
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error = inode->i_op->getxattr(dentry, name, value, size);
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else
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error = -EOPNOTSUPP;
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_getxattr);
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ssize_t
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vfs_listxattr(struct dentry *d, char *list, size_t size)
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{
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ssize_t error;
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error = security_inode_listxattr(d);
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if (error)
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return error;
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error = -EOPNOTSUPP;
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if (d->d_inode->i_op->listxattr) {
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error = d->d_inode->i_op->listxattr(d, list, size);
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} else {
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error = security_inode_listsecurity(d->d_inode, list, size);
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if (size && error > size)
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error = -ERANGE;
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}
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_listxattr);
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int
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vfs_removexattr(struct dentry *dentry, const char *name)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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if (!inode->i_op->removexattr)
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return -EOPNOTSUPP;
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error = xattr_permission(inode, name, MAY_WRITE);
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if (error)
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return error;
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error = security_inode_removexattr(dentry, name);
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if (error)
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return error;
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mutex_lock(&inode->i_mutex);
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error = inode->i_op->removexattr(dentry, name);
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mutex_unlock(&inode->i_mutex);
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if (!error)
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fsnotify_xattr(dentry);
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return error;
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}
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EXPORT_SYMBOL_GPL(vfs_removexattr);
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/*
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* Extended attribute SET operations
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*/
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static long
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setxattr(struct dentry *d, const char __user *name, const void __user *value,
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size_t size, int flags)
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{
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int error;
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void *kvalue = NULL;
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char kname[XATTR_NAME_MAX + 1];
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if (flags & ~(XATTR_CREATE|XATTR_REPLACE))
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return -EINVAL;
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error = strncpy_from_user(kname, name, sizeof(kname));
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if (error == 0 || error == sizeof(kname))
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error = -ERANGE;
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if (error < 0)
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return error;
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if (size) {
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if (size > XATTR_SIZE_MAX)
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return -E2BIG;
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kvalue = memdup_user(value, size);
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if (IS_ERR(kvalue))
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return PTR_ERR(kvalue);
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}
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error = vfs_setxattr(d, kname, kvalue, size, flags);
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kfree(kvalue);
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return error;
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}
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SYSCALL_DEFINE5(setxattr, const char __user *, pathname,
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const char __user *, name, const void __user *, value,
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size_t, size, int, flags)
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{
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struct path path;
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int error;
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error = user_path(pathname, &path);
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if (error)
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return error;
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error = mnt_want_write(path.mnt);
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if (!error) {
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error = setxattr(path.dentry, name, value, size, flags);
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mnt_drop_write(path.mnt);
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}
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE5(lsetxattr, const char __user *, pathname,
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const char __user *, name, const void __user *, value,
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size_t, size, int, flags)
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{
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struct path path;
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int error;
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error = user_lpath(pathname, &path);
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if (error)
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return error;
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error = mnt_want_write(path.mnt);
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if (!error) {
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error = setxattr(path.dentry, name, value, size, flags);
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mnt_drop_write(path.mnt);
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}
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE5(fsetxattr, int, fd, const char __user *, name,
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const void __user *,value, size_t, size, int, flags)
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{
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struct file *f;
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struct dentry *dentry;
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int error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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dentry = f->f_path.dentry;
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audit_inode(NULL, dentry);
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error = mnt_want_write_file(f);
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if (!error) {
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error = setxattr(dentry, name, value, size, flags);
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mnt_drop_write(f->f_path.mnt);
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}
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fput(f);
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return error;
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}
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/*
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* Extended attribute GET operations
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*/
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static ssize_t
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getxattr(struct dentry *d, const char __user *name, void __user *value,
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size_t size)
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{
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ssize_t error;
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void *kvalue = NULL;
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char kname[XATTR_NAME_MAX + 1];
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error = strncpy_from_user(kname, name, sizeof(kname));
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if (error == 0 || error == sizeof(kname))
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error = -ERANGE;
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if (error < 0)
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return error;
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if (size) {
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if (size > XATTR_SIZE_MAX)
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size = XATTR_SIZE_MAX;
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kvalue = kzalloc(size, GFP_KERNEL);
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if (!kvalue)
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return -ENOMEM;
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}
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error = vfs_getxattr(d, kname, kvalue, size);
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if (error > 0) {
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if (size && copy_to_user(value, kvalue, error))
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error = -EFAULT;
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} else if (error == -ERANGE && size >= XATTR_SIZE_MAX) {
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/* The file system tried to returned a value bigger
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than XATTR_SIZE_MAX bytes. Not possible. */
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error = -E2BIG;
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}
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kfree(kvalue);
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return error;
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}
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SYSCALL_DEFINE4(getxattr, const char __user *, pathname,
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const char __user *, name, void __user *, value, size_t, size)
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{
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struct path path;
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ssize_t error;
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error = user_path(pathname, &path);
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if (error)
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return error;
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error = getxattr(path.dentry, name, value, size);
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE4(lgetxattr, const char __user *, pathname,
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const char __user *, name, void __user *, value, size_t, size)
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{
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struct path path;
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ssize_t error;
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error = user_lpath(pathname, &path);
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if (error)
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return error;
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error = getxattr(path.dentry, name, value, size);
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE4(fgetxattr, int, fd, const char __user *, name,
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void __user *, value, size_t, size)
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{
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struct file *f;
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ssize_t error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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audit_inode(NULL, f->f_path.dentry);
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error = getxattr(f->f_path.dentry, name, value, size);
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fput(f);
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return error;
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}
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/*
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* Extended attribute LIST operations
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*/
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static ssize_t
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listxattr(struct dentry *d, char __user *list, size_t size)
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{
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ssize_t error;
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char *klist = NULL;
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if (size) {
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if (size > XATTR_LIST_MAX)
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size = XATTR_LIST_MAX;
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klist = kmalloc(size, GFP_KERNEL);
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if (!klist)
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return -ENOMEM;
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}
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error = vfs_listxattr(d, klist, size);
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if (error > 0) {
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if (size && copy_to_user(list, klist, error))
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error = -EFAULT;
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} else if (error == -ERANGE && size >= XATTR_LIST_MAX) {
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/* The file system tried to returned a list bigger
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than XATTR_LIST_MAX bytes. Not possible. */
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error = -E2BIG;
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}
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kfree(klist);
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return error;
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}
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SYSCALL_DEFINE3(listxattr, const char __user *, pathname, char __user *, list,
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size_t, size)
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{
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struct path path;
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ssize_t error;
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error = user_path(pathname, &path);
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if (error)
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return error;
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error = listxattr(path.dentry, list, size);
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE3(llistxattr, const char __user *, pathname, char __user *, list,
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size_t, size)
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{
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struct path path;
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ssize_t error;
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error = user_lpath(pathname, &path);
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if (error)
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return error;
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error = listxattr(path.dentry, list, size);
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE3(flistxattr, int, fd, char __user *, list, size_t, size)
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{
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struct file *f;
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ssize_t error = -EBADF;
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f = fget(fd);
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if (!f)
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return error;
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audit_inode(NULL, f->f_path.dentry);
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error = listxattr(f->f_path.dentry, list, size);
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fput(f);
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return error;
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}
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/*
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* Extended attribute REMOVE operations
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*/
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static long
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removexattr(struct dentry *d, const char __user *name)
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{
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int error;
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char kname[XATTR_NAME_MAX + 1];
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error = strncpy_from_user(kname, name, sizeof(kname));
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if (error == 0 || error == sizeof(kname))
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error = -ERANGE;
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if (error < 0)
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return error;
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return vfs_removexattr(d, kname);
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}
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SYSCALL_DEFINE2(removexattr, const char __user *, pathname,
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const char __user *, name)
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{
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struct path path;
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int error;
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error = user_path(pathname, &path);
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if (error)
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return error;
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error = mnt_want_write(path.mnt);
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if (!error) {
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error = removexattr(path.dentry, name);
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mnt_drop_write(path.mnt);
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}
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path_put(&path);
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return error;
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}
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SYSCALL_DEFINE2(lremovexattr, const char __user *, pathname,
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const char __user *, name)
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{
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struct path path;
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int error;
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error = user_lpath(pathname, &path);
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if (error)
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return error;
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error = mnt_want_write(path.mnt);
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if (!error) {
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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(f->f_path.mnt);
|
|
}
|
|
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, 0, 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);
|