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)) &&
  53            !inode_capable(inode, CAP_CHOWN))
  54                return -EPERM;
  55
  56        /* Make sure caller can chgrp. */
  57        if ((ia_valid & ATTR_GID) &&
  58            (!uid_eq(current_fsuid(), inode->i_uid) ||
  59            (!in_group_p(attr->ia_gid) && !gid_eq(attr->ia_gid, inode->i_gid))) &&
  60            !inode_capable(inode, CAP_CHOWN))
  61                return -EPERM;
  62
  63        /* Make sure a caller can chmod. */
  64        if (ia_valid & ATTR_MODE) {
  65                if (!inode_owner_or_capable(inode))
  66                        return -EPERM;
  67                /* Also check the setgid bit! */
  68                if (!in_group_p((ia_valid & ATTR_GID) ? attr->ia_gid :
  69                                inode->i_gid) &&
  70                    !inode_capable(inode, CAP_FSETID))
  71                        attr->ia_mode &= ~S_ISGID;
  72        }
  73
  74        /* Check for setting the inode time. */
  75        if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) {
  76                if (!inode_owner_or_capable(inode))
  77                        return -EPERM;
  78        }
  79
  80        return 0;
  81}
  82EXPORT_SYMBOL(inode_change_ok);
  83
  84/**
  85 * inode_newsize_ok - may this inode be truncated to a given size
  86 * @inode:      the inode to be truncated
  87 * @offset:     the new size to assign to the inode
  88 * @Returns:    0 on success, -ve errno on failure
  89 *
  90 * inode_newsize_ok must be called with i_mutex held.
  91 *
  92 * inode_newsize_ok will check filesystem limits and ulimits to check that the
  93 * new inode size is within limits. inode_newsize_ok will also send SIGXFSZ
  94 * when necessary. Caller must not proceed with inode size change if failure is
  95 * returned. @inode must be a file (not directory), with appropriate
  96 * permissions to allow truncate (inode_newsize_ok does NOT check these
  97 * conditions).
  98 */
  99int inode_newsize_ok(const struct inode *inode, loff_t offset)
 100{
 101        if (inode->i_size < offset) {
 102                unsigned long limit;
 103
 104                limit = rlimit(RLIMIT_FSIZE);
 105                if (limit != RLIM_INFINITY && offset > limit)
 106                        goto out_sig;
 107                if (offset > inode->i_sb->s_maxbytes)
 108                        goto out_big;
 109        } else {
 110                /*
 111                 * truncation of in-use swapfiles is disallowed - it would
 112                 * cause subsequent swapout to scribble on the now-freed
 113                 * blocks.
 114                 */
 115                if (IS_SWAPFILE(inode))
 116                        return -ETXTBSY;
 117        }
 118
 119        return 0;
 120out_sig:
 121        send_sig(SIGXFSZ, current, 0);
 122out_big:
 123        return -EFBIG;
 124}
 125EXPORT_SYMBOL(inode_newsize_ok);
 126
 127/**
 128 * setattr_copy - copy simple metadata updates into the generic inode
 129 * @inode:      the inode to be updated
 130 * @attr:       the new attributes
 131 *
 132 * setattr_copy must be called with i_mutex held.
 133 *
 134 * setattr_copy updates the inode's metadata with that specified
 135 * in attr. Noticeably missing is inode size update, which is more complex
 136 * as it requires pagecache updates.
 137 *
 138 * The inode is not marked as dirty after this operation. The rationale is
 139 * that for "simple" filesystems, the struct inode is the inode storage.
 140 * The caller is free to mark the inode dirty afterwards if needed.
 141 */
 142void setattr_copy(struct inode *inode, const struct iattr *attr)
 143{
 144        unsigned int ia_valid = attr->ia_valid;
 145
 146        if (ia_valid & ATTR_UID)
 147                inode->i_uid = attr->ia_uid;
 148        if (ia_valid & ATTR_GID)
 149                inode->i_gid = attr->ia_gid;
 150        if (ia_valid & ATTR_ATIME)
 151                inode->i_atime = timespec_trunc(attr->ia_atime,
 152                                                inode->i_sb->s_time_gran);
 153        if (ia_valid & ATTR_MTIME)
 154                inode->i_mtime = timespec_trunc(attr->ia_mtime,
 155                                                inode->i_sb->s_time_gran);
 156        if (ia_valid & ATTR_CTIME)
 157                inode->i_ctime = timespec_trunc(attr->ia_ctime,
 158                                                inode->i_sb->s_time_gran);
 159        if (ia_valid & ATTR_MODE) {
 160                umode_t mode = attr->ia_mode;
 161
 162                if (!in_group_p(inode->i_gid) &&
 163                    !inode_capable(inode, CAP_FSETID))
 164                        mode &= ~S_ISGID;
 165                inode->i_mode = mode;
 166        }
 167}
 168EXPORT_SYMBOL(setattr_copy);
 169
 170int notify_change(struct dentry * dentry, struct iattr * attr)
 171{
 172        struct inode *inode = dentry->d_inode;
 173        umode_t mode = inode->i_mode;
 174        int error;
 175        struct timespec now;
 176        unsigned int ia_valid = attr->ia_valid;
 177
 178        WARN_ON_ONCE(!mutex_is_locked(&inode->i_mutex));
 179
 180        if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) {
 181                if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
 182                        return -EPERM;
 183        }
 184
 185        if ((ia_valid & ATTR_SIZE) && IS_I_VERSION(inode)) {
 186                if (attr->ia_size != inode->i_size)
 187                        inode_inc_iversion(inode);
 188        }
 189
 190        if ((ia_valid & ATTR_MODE)) {
 191                umode_t amode = attr->ia_mode;
 192                /* Flag setting protected by i_mutex */
 193                if (is_sxid(amode))
 194                        inode->i_flags &= ~S_NOSEC;
 195        }
 196
 197        now = current_fs_time(inode->i_sb);
 198
 199        attr->ia_ctime = now;
 200        if (!(ia_valid & ATTR_ATIME_SET))
 201                attr->ia_atime = now;
 202        if (!(ia_valid & ATTR_MTIME_SET))
 203                attr->ia_mtime = now;
 204        if (ia_valid & ATTR_KILL_PRIV) {
 205                attr->ia_valid &= ~ATTR_KILL_PRIV;
 206                ia_valid &= ~ATTR_KILL_PRIV;
 207                error = security_inode_need_killpriv(dentry);
 208                if (error > 0)
 209                        error = security_inode_killpriv(dentry);
 210                if (error)
 211                        return error;
 212        }
 213
 214        /*
 215         * We now pass ATTR_KILL_S*ID to the lower level setattr function so
 216         * that the function has the ability to reinterpret a mode change
 217         * that's due to these bits. This adds an implicit restriction that
 218         * no function will ever call notify_change with both ATTR_MODE and
 219         * ATTR_KILL_S*ID set.
 220         */
 221        if ((ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID)) &&
 222            (ia_valid & ATTR_MODE))
 223                BUG();
 224
 225        if (ia_valid & ATTR_KILL_SUID) {
 226                if (mode & S_ISUID) {
 227                        ia_valid = attr->ia_valid |= ATTR_MODE;
 228                        attr->ia_mode = (inode->i_mode & ~S_ISUID);
 229                }
 230        }
 231        if (ia_valid & ATTR_KILL_SGID) {
 232                if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
 233                        if (!(ia_valid & ATTR_MODE)) {
 234                                ia_valid = attr->ia_valid |= ATTR_MODE;
 235                                attr->ia_mode = inode->i_mode;
 236                        }
 237                        attr->ia_mode &= ~S_ISGID;
 238                }
 239        }
 240        if (!(attr->ia_valid & ~(ATTR_KILL_SUID | ATTR_KILL_SGID)))
 241                return 0;
 242
 243        error = security_inode_setattr(dentry, attr);
 244        if (error)
 245                return error;
 246
 247        if (inode->i_op->setattr)
 248                error = inode->i_op->setattr(dentry, attr);
 249        else
 250                error = simple_setattr(dentry, attr);
 251
 252        if (!error) {
 253                fsnotify_change(dentry, ia_valid);
 254                ima_inode_post_setattr(dentry);
 255                evm_inode_post_setattr(dentry, ia_valid);
 256        }
 257
 258        return error;
 259}
 260EXPORT_SYMBOL(notify_change);
 261
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