drivers/base/firmware_loader/fallback.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #include <linux/types.h>
   4 #include <linux/kconfig.h>
   5 #include <linux/list.h>
   6 #include <linux/security.h>
   7 #include <linux/umh.h>
   8 #include <linux/sysctl.h>
   9 #include <linux/module.h>
  10
  11 #include "fallback.h"
  12 #include "firmware.h"
  13
  14 /*
  15  * firmware fallback mechanism
  16  */
  17
  18 /*
  19  * use small loading timeout for caching devices' firmware because all these
  20  * firmware images have been loaded successfully at lease once, also system is
  21  * ready for completing firmware loading now. The maximum size of firmware in
  22  * current distributions is about 2M bytes, so 10 secs should be enough.
  23  */
  24 void fw_fallback_set_cache_timeout(void)
  25 {
  26         fw_fallback_config.old_timeout = __firmware_loading_timeout();
  27         __fw_fallback_set_timeout(10);
  28 }
  29
  30 /* Restores the timeout to the value last configured during normal operation */
  31 void fw_fallback_set_default_timeout(void)
  32 {
  33         __fw_fallback_set_timeout(fw_fallback_config.old_timeout);
  34 }
  35
  36 static long firmware_loading_timeout(void)
  37 {
  38         return __firmware_loading_timeout() > 0 ?
  39                 __firmware_loading_timeout() * HZ : MAX_JIFFY_OFFSET;
  40 }
  41
  42 static inline int fw_sysfs_wait_timeout(struct fw_priv *fw_priv,  long timeout)
  43 {
  44         return __fw_state_wait_common(fw_priv, timeout);
  45 }
  46
  47 static LIST_HEAD(pending_fw_head);
  48
  49 void kill_pending_fw_fallback_reqs(bool kill_all)
  50 {
  51         struct fw_priv *fw_priv;
  52         struct fw_priv *next;
  53
  54         mutex_lock(&fw_lock);
  55         list_for_each_entry_safe(fw_priv, next, &pending_fw_head,
  56                                  pending_list) {
  57                 if (kill_all || !fw_priv->need_uevent)
  58                          __fw_load_abort(fw_priv);
  59         }
  60
  61         if (kill_all)
  62                 fw_load_abort_all = true;
  63
  64         mutex_unlock(&fw_lock);
  65 }
  66
  67 /**
  68  * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism
  69  * @fw_sysfs: firmware sysfs information for the firmware to load
  70  * @timeout: timeout to wait for the load
  71  *
  72  * In charge of constructing a sysfs fallback interface for firmware loading.
  73  **/
  74 static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, long timeout)
  75 {
  76         int retval = 0;
  77         struct device *f_dev = &fw_sysfs->dev;
  78         struct fw_priv *fw_priv = fw_sysfs->fw_priv;
  79
  80         /* fall back on userspace loading */
  81         if (!fw_priv->data)
  82                 fw_priv->is_paged_buf = true;
  83
  84         dev_set_uevent_suppress(f_dev, true);
  85
  86         retval = device_add(f_dev);
  87         if (retval) {
  88                 dev_err(f_dev, "%s: device_register failed\n", __func__);
  89                 goto err_put_dev;
  90         }
  91
  92         mutex_lock(&fw_lock);
  93         if (fw_load_abort_all || fw_state_is_aborted(fw_priv)) {
  94                 mutex_unlock(&fw_lock);
  95                 retval = -EINTR;
  96                 goto out;
  97         }
  98         list_add(&fw_priv->pending_list, &pending_fw_head);
  99         mutex_unlock(&fw_lock);
 100
 101         if (fw_priv->opt_flags & FW_OPT_UEVENT) {
 102                 fw_priv->need_uevent = true;
 103                 dev_set_uevent_suppress(f_dev, false);
 104                 dev_dbg(f_dev, "firmware: requesting %s\n", fw_priv->fw_name);
 105                 kobject_uevent(&fw_sysfs->dev.kobj, KOBJ_ADD);
 106         } else {
 107                 timeout = MAX_JIFFY_OFFSET;
 108         }
 109
 110         retval = fw_sysfs_wait_timeout(fw_priv, timeout);
 111         if (retval < 0 && retval != -ENOENT) {
 112                 mutex_lock(&fw_lock);
 113                 fw_load_abort(fw_sysfs);
 114                 mutex_unlock(&fw_lock);
 115         }
 116
 117         if (fw_state_is_aborted(fw_priv)) {
 118                 if (retval == -ERESTARTSYS)
 119                         retval = -EINTR;
 120         } else if (fw_priv->is_paged_buf && !fw_priv->data)
 121                 retval = -ENOMEM;
 122
 123 out:
 124         device_del(f_dev);
 125 err_put_dev:
 126         put_device(f_dev);
 127         return retval;
 128 }
 129
 130 static int fw_load_from_user_helper(struct firmware *firmware,
 131                                     const char *name, struct device *device,
 132                                     u32 opt_flags)
 133 {
 134         struct fw_sysfs *fw_sysfs;
 135         long timeout;
 136         int ret;
 137
 138         timeout = firmware_loading_timeout();
 139         if (opt_flags & FW_OPT_NOWAIT) {
 140                 timeout = usermodehelper_read_lock_wait(timeout);
 141                 if (!timeout) {
 142                         dev_dbg(device, "firmware: %s loading timed out\n",
 143                                 name);
 144                         return -EBUSY;
 145                 }
 146         } else {
 147                 ret = usermodehelper_read_trylock();
 148                 if (WARN_ON(ret)) {
 149                         dev_err(device, "firmware: %s will not be loaded\n",
 150                                 name);
 151                         return ret;
 152                 }
 153         }
 154
 155         fw_sysfs = fw_create_instance(firmware, name, device, opt_flags);
 156         if (IS_ERR(fw_sysfs)) {
 157                 ret = PTR_ERR(fw_sysfs);
 158                 goto out_unlock;
 159         }
 160
 161         fw_sysfs->fw_priv = firmware->priv;
 162         ret = fw_load_sysfs_fallback(fw_sysfs, timeout);
 163
 164         if (!ret)
 165                 ret = assign_fw(firmware, device);
 166
 167 out_unlock:
 168         usermodehelper_read_unlock();
 169
 170         return ret;
 171 }
 172
 173 static bool fw_force_sysfs_fallback(u32 opt_flags)
 174 {
 175         if (fw_fallback_config.force_sysfs_fallback)
 176                 return true;
 177         if (!(opt_flags & FW_OPT_USERHELPER))
 178                 return false;
 179         return true;
 180 }
 181
 182 static bool fw_run_sysfs_fallback(u32 opt_flags)
 183 {
 184         int ret;
 185
 186         if (fw_fallback_config.ignore_sysfs_fallback) {
 187                 pr_info_once("Ignoring firmware sysfs fallback due to sysctl knob\n");
 188                 return false;
 189         }
 190
 191         if ((opt_flags & FW_OPT_NOFALLBACK_SYSFS))
 192                 return false;
 193
 194         /* Also permit LSMs and IMA to fail firmware sysfs fallback */
 195         ret = security_kernel_load_data(LOADING_FIRMWARE, true);
 196         if (ret < 0)
 197                 return false;
 198
 199         return fw_force_sysfs_fallback(opt_flags);
 200 }
 201
 202 /**
 203  * firmware_fallback_sysfs() - use the fallback mechanism to find firmware
 204  * @fw: pointer to firmware image
 205  * @name: name of firmware file to look for
 206  * @device: device for which firmware is being loaded
 207  * @opt_flags: options to control firmware loading behaviour, as defined by
 208  *             &enum fw_opt
 209  * @ret: return value from direct lookup which triggered the fallback mechanism
 210  *
 211  * This function is called if direct lookup for the firmware failed, it enables
 212  * a fallback mechanism through userspace by exposing a sysfs loading
 213  * interface. Userspace is in charge of loading the firmware through the sysfs
 214  * loading interface. This sysfs fallback mechanism may be disabled completely
 215  * on a system by setting the proc sysctl value ignore_sysfs_fallback to true.
 216  * If this is false we check if the internal API caller set the
 217  * @FW_OPT_NOFALLBACK_SYSFS flag, if so it would also disable the fallback
 218  * mechanism. A system may want to enforce the sysfs fallback mechanism at all
 219  * times, it can do this by setting ignore_sysfs_fallback to false and
 220  * force_sysfs_fallback to true.
 221  * Enabling force_sysfs_fallback is functionally equivalent to build a kernel
 222  * with CONFIG_FW_LOADER_USER_HELPER_FALLBACK.
 223  **/
 224 int firmware_fallback_sysfs(struct firmware *fw, const char *name,
 225                             struct device *device,
 226                             u32 opt_flags,
 227                             int ret)
 228 {
 229         if (!fw_run_sysfs_fallback(opt_flags))
 230                 return ret;
 231
 232         if (!(opt_flags & FW_OPT_NO_WARN))
 233                 dev_warn(device, "Falling back to sysfs fallback for: %s\n",
 234                                  name);
 235         else
 236                 dev_dbg(device, "Falling back to sysfs fallback for: %s\n",
 237                                 name);
 238         return fw_load_from_user_helper(fw, name, device, opt_flags);
 239 }