fs/cachefiles/xattr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* CacheFiles extended attribute management
   3  *
   4  * Copyright (C) 2021 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/module.h>
   9 #include <linux/sched.h>
  10 #include <linux/file.h>
  11 #include <linux/fs.h>
  12 #include <linux/fsnotify.h>
  13 #include <linux/quotaops.h>
  14 #include <linux/xattr.h>
  15 #include <linux/slab.h>
  16 #include "internal.h"
  17
  18 #define CACHEFILES_COOKIE_TYPE_DATA 1
  19
  20 struct cachefiles_xattr {
  21         __be64  object_size;    /* Actual size of the object */
  22         __be64  zero_point;     /* Size after which server has no data not written by us */
  23         __u8    type;           /* Type of object */
  24         __u8    content;        /* Content presence (enum cachefiles_content) */
  25         __u8    data[];         /* netfs coherency data */
  26 } __packed;
  27
  28 static const char cachefiles_xattr_cache[] =
  29         XATTR_USER_PREFIX "CacheFiles.cache";
  30
  31 struct cachefiles_vol_xattr {
  32         __be32  reserved;       /* Reserved, should be 0 */
  33         __u8    data[];         /* netfs volume coherency data */
  34 } __packed;
  35
  36 /*
  37  * set the state xattr on a cache file
  38  */
  39 int cachefiles_set_object_xattr(struct cachefiles_object *object)
  40 {
  41         struct cachefiles_xattr *buf;
  42         struct dentry *dentry;
  43         struct file *file = object->file;
  44         unsigned int len = object->cookie->aux_len;
  45         int ret;
  46
  47         if (!file)
  48                 return -ESTALE;
  49         dentry = file->f_path.dentry;
  50
  51         _enter("%x,#%d", object->debug_id, len);
  52
  53         buf = kmalloc(sizeof(struct cachefiles_xattr) + len, GFP_KERNEL);
  54         if (!buf)
  55                 return -ENOMEM;
  56
  57         buf->object_size        = cpu_to_be64(object->cookie->object_size);
  58         buf->zero_point         = 0;
  59         buf->type               = CACHEFILES_COOKIE_TYPE_DATA;
  60         buf->content            = object->content_info;
  61         if (test_bit(FSCACHE_COOKIE_LOCAL_WRITE, &object->cookie->flags))
  62                 buf->content    = CACHEFILES_CONTENT_DIRTY;
  63         if (len > 0)
  64                 memcpy(buf->data, fscache_get_aux(object->cookie), len);
  65
  66         ret = cachefiles_inject_write_error();
  67         if (ret == 0)
  68                 ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
  69                                    buf, sizeof(struct cachefiles_xattr) + len, 0);
  70         if (ret < 0) {
  71                 trace_cachefiles_vfs_error(object, file_inode(file), ret,
  72                                            cachefiles_trace_setxattr_error);
  73                 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
  74                                            buf->content,
  75                                            cachefiles_coherency_set_fail);
  76                 if (ret != -ENOMEM)
  77                         cachefiles_io_error_obj(
  78                                 object,
  79                                 "Failed to set xattr with error %d", ret);
  80         } else {
  81                 trace_cachefiles_coherency(object, file_inode(file)->i_ino,
  82                                            buf->content,
  83                                            cachefiles_coherency_set_ok);
  84         }
  85
  86         kfree(buf);
  87         _leave(" = %d", ret);
  88         return ret;
  89 }
  90
  91 /*
  92  * check the consistency between the backing cache and the FS-Cache cookie
  93  */
  94 int cachefiles_check_auxdata(struct cachefiles_object *object, struct file *file)
  95 {
  96         struct cachefiles_xattr *buf;
  97         struct dentry *dentry = file->f_path.dentry;
  98         unsigned int len = object->cookie->aux_len, tlen;
  99         const void *p = fscache_get_aux(object->cookie);
 100         enum cachefiles_coherency_trace why;
 101         ssize_t xlen;
 102         int ret = -ESTALE;
 103
 104         tlen = sizeof(struct cachefiles_xattr) + len;
 105         buf = kmalloc(tlen, GFP_KERNEL);
 106         if (!buf)
 107                 return -ENOMEM;
 108
 109         xlen = cachefiles_inject_read_error();
 110         if (xlen == 0)
 111                 xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, tlen);
 112         if (xlen != tlen) {
 113                 if (xlen < 0)
 114                         trace_cachefiles_vfs_error(object, file_inode(file), xlen,
 115                                                    cachefiles_trace_getxattr_error);
 116                 if (xlen == -EIO)
 117                         cachefiles_io_error_obj(
 118                                 object,
 119                                 "Failed to read aux with error %zd", xlen);
 120                 why = cachefiles_coherency_check_xattr;
 121         } else if (buf->type != CACHEFILES_COOKIE_TYPE_DATA) {
 122                 why = cachefiles_coherency_check_type;
 123         } else if (memcmp(buf->data, p, len) != 0) {
 124                 why = cachefiles_coherency_check_aux;
 125         } else if (be64_to_cpu(buf->object_size) != object->cookie->object_size) {
 126                 why = cachefiles_coherency_check_objsize;
 127         } else if (buf->content == CACHEFILES_CONTENT_DIRTY) {
 128                 // TODO: Begin conflict resolution
 129                 pr_warn("Dirty object in cache\n");
 130                 why = cachefiles_coherency_check_dirty;
 131         } else {
 132                 why = cachefiles_coherency_check_ok;
 133                 ret = 0;
 134         }
 135
 136         trace_cachefiles_coherency(object, file_inode(file)->i_ino,
 137                                    buf->content, why);
 138         kfree(buf);
 139         return ret;
 140 }
 141
 142 /*
 143  * remove the object's xattr to mark it stale
 144  */
 145 int cachefiles_remove_object_xattr(struct cachefiles_cache *cache,
 146                                    struct cachefiles_object *object,
 147                                    struct dentry *dentry)
 148 {
 149         int ret;
 150
 151         ret = cachefiles_inject_remove_error();
 152         if (ret == 0)
 153                 ret = vfs_removexattr(&init_user_ns, dentry, cachefiles_xattr_cache);
 154         if (ret < 0) {
 155                 trace_cachefiles_vfs_error(object, d_inode(dentry), ret,
 156                                            cachefiles_trace_remxattr_error);
 157                 if (ret == -ENOENT || ret == -ENODATA)
 158                         ret = 0;
 159                 else if (ret != -ENOMEM)
 160                         cachefiles_io_error(cache,
 161                                             "Can't remove xattr from %lu"
 162                                             " (error %d)",
 163                                             d_backing_inode(dentry)->i_ino, -ret);
 164         }
 165
 166         _leave(" = %d", ret);
 167         return ret;
 168 }
 169
 170 /*
 171  * Stick a marker on the cache object to indicate that it's dirty.
 172  */
 173 void cachefiles_prepare_to_write(struct fscache_cookie *cookie)
 174 {
 175         const struct cred *saved_cred;
 176         struct cachefiles_object *object = cookie->cache_priv;
 177         struct cachefiles_cache *cache = object->volume->cache;
 178
 179         _enter("c=%08x", object->cookie->debug_id);
 180
 181         if (!test_bit(CACHEFILES_OBJECT_USING_TMPFILE, &object->flags)) {
 182                 cachefiles_begin_secure(cache, &saved_cred);
 183                 cachefiles_set_object_xattr(object);
 184                 cachefiles_end_secure(cache, saved_cred);
 185         }
 186 }
 187
 188 /*
 189  * Set the state xattr on a volume directory.
 190  */
 191 bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)
 192 {
 193         struct cachefiles_vol_xattr *buf;
 194         unsigned int len = volume->vcookie->coherency_len;
 195         const void *p = volume->vcookie->coherency;
 196         struct dentry *dentry = volume->dentry;
 197         int ret;
 198
 199         _enter("%x,#%d", volume->vcookie->debug_id, len);
 200
 201         len += sizeof(*buf);
 202         buf = kmalloc(len, GFP_KERNEL);
 203         if (!buf)
 204                 return false;
 205         buf->reserved = cpu_to_be32(0);
 206         memcpy(buf->data, p, len);
 207
 208         ret = cachefiles_inject_write_error();
 209         if (ret == 0)
 210                 ret = vfs_setxattr(&init_user_ns, dentry, cachefiles_xattr_cache,
 211                                    buf, len, 0);
 212         if (ret < 0) {
 213                 trace_cachefiles_vfs_error(NULL, d_inode(dentry), ret,
 214                                            cachefiles_trace_setxattr_error);
 215                 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
 216                                                cachefiles_coherency_vol_set_fail);
 217                 if (ret != -ENOMEM)
 218                         cachefiles_io_error(
 219                                 volume->cache, "Failed to set xattr with error %d", ret);
 220         } else {
 221                 trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino,
 222                                                cachefiles_coherency_vol_set_ok);
 223         }
 224
 225         kfree(buf);
 226         _leave(" = %d", ret);
 227         return ret == 0;
 228 }
 229
 230 /*
 231  * Check the consistency between the backing cache and the volume cookie.
 232  */
 233 int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
 234 {
 235         struct cachefiles_vol_xattr *buf;
 236         struct dentry *dentry = volume->dentry;
 237         unsigned int len = volume->vcookie->coherency_len;
 238         const void *p = volume->vcookie->coherency;
 239         enum cachefiles_coherency_trace why;
 240         ssize_t xlen;
 241         int ret = -ESTALE;
 242
 243         _enter("");
 244
 245         len += sizeof(*buf);
 246         buf = kmalloc(len, GFP_KERNEL);
 247         if (!buf)
 248                 return -ENOMEM;
 249
 250         xlen = cachefiles_inject_read_error();
 251         if (xlen == 0)
 252                 xlen = vfs_getxattr(&init_user_ns, dentry, cachefiles_xattr_cache, buf, len);
 253         if (xlen != len) {
 254                 if (xlen < 0) {
 255                         trace_cachefiles_vfs_error(NULL, d_inode(dentry), xlen,
 256                                                    cachefiles_trace_getxattr_error);
 257                         if (xlen == -EIO)
 258                                 cachefiles_io_error(
 259                                         volume->cache,
 260                                         "Failed to read xattr with error %zd", xlen);
 261                 }
 262                 why = cachefiles_coherency_vol_check_xattr;
 263         } else if (buf->reserved != cpu_to_be32(0)) {
 264                 why = cachefiles_coherency_vol_check_resv;
 265         } else if (memcmp(buf->data, p, len - sizeof(*buf)) != 0) {
 266                 why = cachefiles_coherency_vol_check_cmp;
 267         } else {
 268                 why = cachefiles_coherency_vol_check_ok;
 269                 ret = 0;
 270         }
 271
 272         trace_cachefiles_vol_coherency(volume, d_inode(dentry)->i_ino, why);
 273         kfree(buf);
 274         _leave(" = %d", ret);
 275         return ret;
 276 }