linux/fs/attr.c
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   1/*
   2 *  linux/fs/attr.c
   3 *
   4 *  Copyright (C) 1991, 1992  Linus Torvalds
   5 *  changes by Thomas Schoebel-Theuer
   6 */
   7
   8#include <linux/export.h>
   9#include <linux/time.h>
  10#include <linux/mm.h>
  11#include <linux/string.h>
  12#include <linux/capability.h>
  13#include <linux/fsnotify.h>
  14#include <linux/fcntl.h>
  15#include <linux/security.h>
  16#include <linux/evm.h>
  17#include <linux/ima.h>
  18
  19/**
  20 * inode_change_ok - check if attribute changes to an inode are allowed
  21 * @inode:      inode to check
  22 * @attr:       attributes to change
  23 *
  24 * Check if we are allowed to change the attributes contained in @attr
  25 * in the given inode.  This includes the normal unix access permission
  26 * checks, as well as checks for rlimits and others.
  27 *
  28 * Should be called as the first thing in ->setattr implementations,
  29 * possibly after taking additional locks.
  30 */
  31int inode_change_ok(const struct inode *inode, struct iattr *attr)
  32{
  33        unsigned int ia_valid = attr->ia_valid;
  34
  35        /*
  36         * First check size constraints.  These can't be overriden using
  37         * ATTR_FORCE.
  38         */
  39        if (ia_valid & ATTR_SIZE) {
  40                int error = inode_newsize_ok(inode, attr->ia_size);
  41                if (error)
  42                        return error;
  43        }
  44
  45        /* If force is set do it anyway. */
  46        if (ia_valid & ATTR_FORCE)
  47                return 0;
  48
  49        /* Make sure a caller can chown. */
  50        if ((ia_valid & ATTR_UID) &&
  51            (!uid_eq(current_fsuid(), inode->i_uid) ||
  52             !uid_eq(attr->ia_uid, inode->i_uid)) && !capable(CAP_CHOWN))
  53                return -EPERM;
  54
  55        /* Make sure caller can chgrp. */
  56        if ((ia_valid & ATTR_GID) &&
  57            (!uid_eq(current_fsuid(), inode->i_uid) ||
  58            (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
  59            !capable(CAP_CHOWN))
  60                return -EPERM;
  61
  62        /* Make sure a caller can chmod. */
  63        if (ia_valid & ATTR_MODE) {
  64                if (!inode_owner_or_capable(inode))
  65                        return -EPERM;
  66                /* Also check the setgid bit! */
  67                if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
  68                                inode->i_gid) && !capable(CAP_FSETID))
  69                        attr->ia_mode &= ~S_ISGID;
  70        }
  71
  72        /* Check for setting the inode time. */
  73        if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
  74                if (!inode_owner_or_capable(inode))
  75                        return -EPERM;
  76        }
  77
  78        return 0;
  79}
  80EXPORT_SYMBOL(inode_change_ok);
  81
  82/**
  83 * inode_newsize_ok - may this inode be truncated to a given size
  84 * @inode:      the inode to be truncated
  85 * @offset:     the new size to assign to the inode
  86 * @Returns:    0 on success, -ve errno on failure
  87 *
  88 * inode_newsize_ok must be called with i_mutex held.
  89 *
  90 * inode_newsize_ok will check filesystem limits and ulimits to check that the
  91 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
  92 * when necessary. Caller must not proceed with inode size change if failure is
  93 * returned. @inode must be a file (not directory), with appropriate
  94 * permissions to allow truncate (inode_newsize_ok does NOT check these
  95 * conditions).
  96 */
  97int inode_newsize_ok(const struct inode *inode, loff_t offset)
  98{
  99        if (inode->i_size < offset) {
 100                unsigned long limit;
 101
 102                limit = rlimit(RLIMIT_FSIZE);
 103                if (limit != RLIM_INFINITY && offset > limit)
 104                        goto out_sig;
 105                if (offset > inode->i_sb->s_maxbytes)
 106                        goto out_big;
 107        } else {
 108                /*
 109                 * truncation of in-use swapfiles is disallowed - it would
 110                 * cause subsequent swapout to scribble on the now-freed
 111                 * blocks.
 112                 */
 113                if (IS_SWAPFILE(inode))
 114                        return -ETXTBSY;
 115        }
 116
 117        return 0;
 118out_sig:
 119        send_sig(SIGXFSZ, current, 0);
 120out_big:
 121        return -EFBIG;
 122}
 123EXPORT_SYMBOL(inode_newsize_ok);
 124
 125/**
 126 * setattr_copy - copy simple metadata updates into the generic inode
 127 * @inode:      the inode to be updated
 128 * @attr:       the new attributes
 129 *
 130 * setattr_copy must be called with i_mutex held.
 131 *
 132 * setattr_copy updates the inode's metadata with that specified
 133 * in attr. Noticeably missing is inode size update, which is more complex
 134 * as it requires pagecache updates.
 135 *
 136 * The inode is not marked as dirty after this operation. The rationale is
 137 * that for "simple" filesystems, the struct inode is the inode storage.
 138 * The caller is free to mark the inode dirty afterwards if needed.
 139 */
 140void setattr_copy(struct inode *inode, const struct iattr *attr)
 141{
 142        unsigned int ia_valid = attr->ia_valid;
 143
 144        if (ia_valid & ATTR_UID)
 145                inode->i_uid = attr->ia_uid;
 146        if (ia_valid & ATTR_GID)
 147                inode->i_gid = attr->ia_gid;
 148        if (ia_valid & ATTR_ATIME)
 149                inode->i_atime = timespec_trunc(attr->ia_atime,
 150                                                inode->i_sb->s_time_gran);
 151        if (ia_valid & ATTR_MTIME)
 152                inode->i_mtime = timespec_trunc(attr->ia_mtime,
 153                                                inode->i_sb->s_time_gran);
 154        if (ia_valid & ATTR_CTIME)
 155                inode->i_ctime = timespec_trunc(attr->ia_ctime,
 156                                                inode->i_sb->s_time_gran);
 157        if (ia_valid & ATTR_MODE) {
 158                umode_t mode = attr->ia_mode;
 159
 160                if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
 161                        mode &= ~S_ISGID;
 162                inode->i_mode = mode;
 163        }
 164}
 165EXPORT_SYMBOL(setattr_copy);
 166
 167int notify_change(struct dentry * dentry, struct iattr * attr)
 168{
 169        struct inode *inode = dentry->d_inode;
 170        umode_t mode = inode->i_mode;
 171        int error;
 172        struct timespec now;
 173        unsigned int ia_valid = attr->ia_valid;
 174
 175        WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
 176
 177        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
 178                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 179                        return -EPERM;
 180        }
 181
 182        if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
 183                if (attr->ia_size != inode->i_size)
 184                        inode_inc_iversion(inode);
 185        }
 186
 187        if ((ia_valid & ATTR_MODE)) {
 188                umode_t amode = attr->ia_mode;
 189                /* Flag setting protected by i_mutex */
 190                if (is_sxid(amode))
 191                        inode->i_flags &= ~S_NOSEC;
 192        }
 193
 194        now = current_fs_time(inode->i_sb);
 195
 196        attr->ia_ctime = now;
 197        if (!(ia_valid & ATTR_ATIME_SET))
 198                attr->ia_atime = now;
 199        if (!(ia_valid & ATTR_MTIME_SET))
 200                attr->ia_mtime = now;
 201        if (ia_valid & ATTR_KILL_PRIV) {
 202                attr->ia_valid &= ~ATTR_KILL_PRIV;
 203                ia_valid &= ~ATTR_KILL_PRIV;
 204                error = security_inode_need_killpriv(dentry);
 205                if (error > 0)
 206                        error = security_inode_killpriv(dentry);
 207                if (error)
 208                        return error;
 209        }
 210
 211        /*
 212         * We now pass ATTR_KILL_S*ID to the lower level setattr function so
 213         * that the function has the ability to reinterpret a mode change
 214         * that's due to these bits. This adds an implicit restriction that
 215         * no function will ever call notify_change with both ATTR_MODE and
 216         * ATTR_KILL_S*ID set.
 217         */
 218        if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
 219            (ia_valid & ATTR_MODE))
 220                BUG();
 221
 222        if (ia_valid & ATTR_KILL_SUID) {
 223                if (mode & S_ISUID) {
 224                        ia_valid = attr->ia_valid |= ATTR_MODE;
 225                        attr->ia_mode = (inode->i_mode & ~S_ISUID);
 226                }
 227        }
 228        if (ia_valid & ATTR_KILL_SGID) {
 229                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
 230                        if (!(ia_valid & ATTR_MODE)) {
 231                                ia_valid = attr->ia_valid |= ATTR_MODE;
 232                                attr->ia_mode = inode->i_mode;
 233                        }
 234                        attr->ia_mode &= ~S_ISGID;
 235                }
 236        }
 237        if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
 238                return 0;
 239
 240        error = security_inode_setattr(dentry, attr);
 241        if (error)
 242                return error;
 243
 244        if (inode->i_op->setattr)
 245                error = inode->i_op->setattr(dentry, attr);
 246        else
 247                error = simple_setattr(dentry, attr);
 248
 249        if (!error) {
 250                fsnotify_change(dentry, ia_valid);
 251                ima_inode_post_setattr(dentry);
 252                evm_inode_post_setattr(dentry, ia_valid);
 253        }
 254
 255        return error;
 256}
 257EXPORT_SYMBOL(notify_change);
 258
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