fs/xfs/xfs_xattr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2008 Christoph Hellwig.
   4  * Portions Copyright (C) 2000-2008 Silicon Graphics, Inc.
   5  */
   6
   7 #include "xfs.h"
   8 #include "xfs_shared.h"
   9 #include "xfs_format.h"
  10 #include "xfs_log_format.h"
  11 #include "xfs_da_format.h"
  12 #include "xfs_trans_resv.h"
  13 #include "xfs_mount.h"
  14 #include "xfs_inode.h"
  15 #include "xfs_da_btree.h"
  16 #include "xfs_attr.h"
  17 #include "xfs_acl.h"
  18 #include "xfs_log.h"
  19 #include "xfs_xattr.h"
  20 #include "xfs_quota.h"
  21
  22 #include <linux/posix_acl_xattr.h>
  23
  24 /*
  25  * Get permission to use log-assisted atomic exchange of file extents.
  26  * Callers must not be running any transactions or hold any ILOCKs.
  27  */
  28 static inline int
  29 xfs_attr_grab_log_assist(
  30         struct xfs_mount        *mp)
  31 {
  32         int                     error = 0;
  33
  34         /* xattr update log intent items are already enabled */
  35         if (xfs_is_using_logged_xattrs(mp))
  36                 return 0;
  37
  38         /*
  39          * Check if the filesystem featureset is new enough to set this log
  40          * incompat feature bit.  Strictly speaking, the minimum requirement is
  41          * a V5 filesystem for the superblock field, but we'll require rmap
  42          * or reflink to avoid having to deal with really old kernels.
  43          */
  44         if (!xfs_has_reflink(mp) && !xfs_has_rmapbt(mp))
  45                 return -EOPNOTSUPP;
  46
  47         /* Enable log-assisted xattrs. */
  48         error = xfs_add_incompat_log_feature(mp,
  49                         XFS_SB_FEAT_INCOMPAT_LOG_XATTRS);
  50         if (error)
  51                 return error;
  52         xfs_set_using_logged_xattrs(mp);
  53
  54         xfs_warn_experimental(mp, XFS_EXPERIMENTAL_LARP);
  55
  56         return 0;
  57 }
  58
  59 static inline bool
  60 xfs_attr_want_log_assist(
  61         struct xfs_mount        *mp)
  62 {
  63 #ifdef DEBUG
  64         /* Logged xattrs require a V5 super for log_incompat */
  65         return xfs_has_crc(mp) && xfs_globals.larp;
  66 #else
  67         return false;
  68 #endif
  69 }
  70
  71 /*
  72  * Set or remove an xattr, having grabbed the appropriate logging resources
  73  * prior to calling libxfs.  Callers of this function are only required to
  74  * initialize the inode, attr_filter, name, namelen, value, and valuelen fields
  75  * of @args.
  76  */
  77 int
  78 xfs_attr_change(
  79         struct xfs_da_args      *args,
  80         enum xfs_attr_update    op)
  81 {
  82         struct xfs_mount        *mp = args->dp->i_mount;
  83         int                     error;
  84
  85         if (xfs_is_shutdown(mp))
  86                 return -EIO;
  87
  88         error = xfs_qm_dqattach(args->dp);
  89         if (error)
  90                 return error;
  91
  92         /*
  93          * We have no control over the attribute names that userspace passes us
  94          * to remove, so we have to allow the name lookup prior to attribute
  95          * removal to fail as well.
  96          */
  97         args->op_flags = XFS_DA_OP_OKNOENT;
  98
  99         if (xfs_attr_want_log_assist(mp)) {
 100                 error = xfs_attr_grab_log_assist(mp);
 101                 if (error)
 102                         return error;
 103
 104                 args->op_flags |= XFS_DA_OP_LOGGED;
 105         }
 106
 107         args->owner = args->dp->i_ino;
 108         args->geo = mp->m_attr_geo;
 109         args->whichfork = XFS_ATTR_FORK;
 110         xfs_attr_sethash(args);
 111
 112         /*
 113          * Some xattrs must be resistant to allocation failure at ENOSPC, e.g.
 114          * creating an inode with ACLs or security attributes requires the
 115          * allocation of the xattr holding that information to succeed. Hence
 116          * we allow xattrs in the VFS TRUSTED, SYSTEM, POSIX_ACL and SECURITY
 117          * (LSM xattr) namespaces to dip into the reserve block pool to allow
 118          * manipulation of these xattrs when at ENOSPC. These VFS xattr
 119          * namespaces translate to the XFS_ATTR_ROOT and XFS_ATTR_SECURE on-disk
 120          * namespaces.
 121          *
 122          * For most of these cases, these special xattrs will fit in the inode
 123          * itself and so consume no extra space or only require temporary extra
 124          * space while an overwrite is being made. Hence the use of the reserved
 125          * pool is largely to avoid the worst case reservation from preventing
 126          * the xattr from being created at ENOSPC.
 127          */
 128         return xfs_attr_set(args, op,
 129                         args->attr_filter & (XFS_ATTR_ROOT | XFS_ATTR_SECURE));
 130 }
 131
 132
 133 static int
 134 xfs_xattr_get(const struct xattr_handler *handler, struct dentry *unused,
 135                 struct inode *inode, const char *name, void *value, size_t size)
 136 {
 137         struct xfs_da_args      args = {
 138                 .dp             = XFS_I(inode),
 139                 .attr_filter    = handler->flags,
 140                 .name           = name,
 141                 .namelen        = strlen(name),
 142                 .value          = value,
 143                 .valuelen       = size,
 144         };
 145         int                     error;
 146
 147         if (xfs_ifork_zapped(XFS_I(inode), XFS_ATTR_FORK))
 148                 return -EIO;
 149
 150         error = xfs_attr_get(&args);
 151         if (error)
 152                 return error;
 153         return args.valuelen;
 154 }
 155
 156 static inline enum xfs_attr_update
 157 xfs_xattr_flags_to_op(
 158         int             flags,
 159         const void      *value)
 160 {
 161         if (!value)
 162                 return XFS_ATTRUPDATE_REMOVE;
 163         if (flags & XATTR_CREATE)
 164                 return XFS_ATTRUPDATE_CREATE;
 165         if (flags & XATTR_REPLACE)
 166                 return XFS_ATTRUPDATE_REPLACE;
 167         return XFS_ATTRUPDATE_UPSERT;
 168 }
 169
 170 static int
 171 xfs_xattr_set(const struct xattr_handler *handler,
 172               struct mnt_idmap *idmap, struct dentry *unused,
 173               struct inode *inode, const char *name, const void *value,
 174               size_t size, int flags)
 175 {
 176         struct xfs_da_args      args = {
 177                 .dp             = XFS_I(inode),
 178                 .attr_filter    = handler->flags,
 179                 .name           = name,
 180                 .namelen        = strlen(name),
 181                 .value          = (void *)value,
 182                 .valuelen       = size,
 183         };
 184         int                     error;
 185
 186         error = xfs_attr_change(&args, xfs_xattr_flags_to_op(flags, value));
 187         if (!error && (handler->flags & XFS_ATTR_ROOT))
 188                 xfs_forget_acl(inode, name);
 189         return error;
 190 }
 191
 192 static const struct xattr_handler xfs_xattr_user_handler = {
 193         .prefix = XATTR_USER_PREFIX,
 194         .flags  = 0, /* no flags implies user namespace */
 195         .get    = xfs_xattr_get,
 196         .set    = xfs_xattr_set,
 197 };
 198
 199 static const struct xattr_handler xfs_xattr_trusted_handler = {
 200         .prefix = XATTR_TRUSTED_PREFIX,
 201         .flags  = XFS_ATTR_ROOT,
 202         .get    = xfs_xattr_get,
 203         .set    = xfs_xattr_set,
 204 };
 205
 206 static const struct xattr_handler xfs_xattr_security_handler = {
 207         .prefix = XATTR_SECURITY_PREFIX,
 208         .flags  = XFS_ATTR_SECURE,
 209         .get    = xfs_xattr_get,
 210         .set    = xfs_xattr_set,
 211 };
 212
 213 const struct xattr_handler * const xfs_xattr_handlers[] = {
 214         &xfs_xattr_user_handler,
 215         &xfs_xattr_trusted_handler,
 216         &xfs_xattr_security_handler,
 217         NULL
 218 };
 219
 220 static void
 221 __xfs_xattr_put_listent(
 222         struct xfs_attr_list_context *context,
 223         char *prefix,
 224         int prefix_len,
 225         unsigned char *name,
 226         int namelen)
 227 {
 228         char *offset;
 229         int arraytop;
 230
 231         if (context->count < 0 || context->seen_enough)
 232                 return;
 233
 234         if (!context->buffer)
 235                 goto compute_size;
 236
 237         arraytop = context->count + prefix_len + namelen + 1;
 238         if (arraytop > context->firstu) {
 239                 context->count = -1;    /* insufficient space */
 240                 context->seen_enough = 1;
 241                 return;
 242         }
 243         offset = context->buffer + context->count;
 244         memcpy(offset, prefix, prefix_len);
 245         offset += prefix_len;
 246         strncpy(offset, (char *)name, namelen);                 /* real name */
 247         offset += namelen;
 248         *offset = '\0';
 249
 250 compute_size:
 251         context->count += prefix_len + namelen + 1;
 252         return;
 253 }
 254
 255 static void
 256 xfs_xattr_put_listent(
 257         struct xfs_attr_list_context *context,
 258         int             flags,
 259         unsigned char   *name,
 260         int             namelen,
 261         void            *value,
 262         int             valuelen)
 263 {
 264         char *prefix;
 265         int prefix_len;
 266
 267         ASSERT(context->count >= 0);
 268
 269         /* Don't expose private xattr namespaces. */
 270         if (flags & XFS_ATTR_PRIVATE_NSP_MASK)
 271                 return;
 272
 273         if (flags & XFS_ATTR_ROOT) {
 274 #ifdef CONFIG_XFS_POSIX_ACL
 275                 if (namelen == SGI_ACL_FILE_SIZE &&
 276                     strncmp(name, SGI_ACL_FILE,
 277                             SGI_ACL_FILE_SIZE) == 0) {
 278                         __xfs_xattr_put_listent(
 279                                         context, XATTR_SYSTEM_PREFIX,
 280                                         XATTR_SYSTEM_PREFIX_LEN,
 281                                         XATTR_POSIX_ACL_ACCESS,
 282                                         strlen(XATTR_POSIX_ACL_ACCESS));
 283                 } else if (namelen == SGI_ACL_DEFAULT_SIZE &&
 284                          strncmp(name, SGI_ACL_DEFAULT,
 285                                  SGI_ACL_DEFAULT_SIZE) == 0) {
 286                         __xfs_xattr_put_listent(
 287                                         context, XATTR_SYSTEM_PREFIX,
 288                                         XATTR_SYSTEM_PREFIX_LEN,
 289                                         XATTR_POSIX_ACL_DEFAULT,
 290                                         strlen(XATTR_POSIX_ACL_DEFAULT));
 291                 }
 292 #endif
 293
 294                 /*
 295                  * Only show root namespace entries if we are actually allowed to
 296                  * see them.
 297                  */
 298                 if (!capable(CAP_SYS_ADMIN))
 299                         return;
 300
 301                 prefix = XATTR_TRUSTED_PREFIX;
 302                 prefix_len = XATTR_TRUSTED_PREFIX_LEN;
 303         } else if (flags & XFS_ATTR_SECURE) {
 304                 prefix = XATTR_SECURITY_PREFIX;
 305                 prefix_len = XATTR_SECURITY_PREFIX_LEN;
 306         } else {
 307                 prefix = XATTR_USER_PREFIX;
 308                 prefix_len = XATTR_USER_PREFIX_LEN;
 309         }
 310
 311         __xfs_xattr_put_listent(context, prefix, prefix_len, name,
 312                                 namelen);
 313         return;
 314 }
 315
 316 ssize_t
 317 xfs_vn_listxattr(
 318         struct dentry   *dentry,
 319         char            *data,
 320         size_t          size)
 321 {
 322         struct xfs_attr_list_context context;
 323         struct inode    *inode = d_inode(dentry);
 324         int             error;
 325
 326         if (xfs_ifork_zapped(XFS_I(inode), XFS_ATTR_FORK))
 327                 return -EIO;
 328
 329         /*
 330          * First read the regular on-disk attributes.
 331          */
 332         memset(&context, 0, sizeof(context));
 333         context.dp = XFS_I(inode);
 334         context.resynch = 1;
 335         context.buffer = size ? data : NULL;
 336         context.bufsize = size;
 337         context.firstu = context.bufsize;
 338         context.put_listent = xfs_xattr_put_listent;
 339
 340         error = xfs_attr_list(&context);
 341         if (error)
 342                 return error;
 343         if (context.count < 0)
 344                 return -ERANGE;
 345
 346         return context.count;
 347 }