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 only_kill_custom) 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 (!fw_priv->need_uevent || !only_kill_custom) 58 __fw_load_abort(fw_priv); 59 } 60 mutex_unlock(&fw_lock); 61 } 62 63 /** 64 * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism 65 * @fw_sysfs: firmware sysfs information for the firmware to load 66 * @timeout: timeout to wait for the load 67 * 68 * In charge of constructing a sysfs fallback interface for firmware loading. 69 **/ 70 static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, long timeout) 71 { 72 int retval = 0; 73 struct device *f_dev = &fw_sysfs->dev; 74 struct fw_priv *fw_priv = fw_sysfs->fw_priv; 75 76 /* fall back on userspace loading */ 77 if (!fw_priv->data) 78 fw_priv->is_paged_buf = true; 79 80 dev_set_uevent_suppress(f_dev, true); 81 82 retval = device_add(f_dev); 83 if (retval) { 84 dev_err(f_dev, "%s: device_register failed\n", __func__); 85 goto err_put_dev; 86 } 87 88 mutex_lock(&fw_lock); 89 if (fw_state_is_aborted(fw_priv)) { 90 mutex_unlock(&fw_lock); 91 retval = -EINTR; 92 goto out; 93 } 94 list_add(&fw_priv->pending_list, &pending_fw_head); 95 mutex_unlock(&fw_lock); 96 97 if (fw_priv->opt_flags & FW_OPT_UEVENT) { 98 fw_priv->need_uevent = true; 99 dev_set_uevent_suppress(f_dev, false); 100 dev_dbg(f_dev, "firmware: requesting %s\n", fw_priv->fw_name); 101 kobject_uevent(&fw_sysfs->dev.kobj, KOBJ_ADD); 102 } else { 103 timeout = MAX_JIFFY_OFFSET; 104 } 105 106 retval = fw_sysfs_wait_timeout(fw_priv, timeout); 107 if (retval < 0 && retval != -ENOENT) { 108 mutex_lock(&fw_lock); 109 fw_load_abort(fw_sysfs); 110 mutex_unlock(&fw_lock); 111 } 112 113 if (fw_state_is_aborted(fw_priv)) { 114 if (retval == -ERESTARTSYS) 115 retval = -EINTR; 116 } else if (fw_priv->is_paged_buf && !fw_priv->data) 117 retval = -ENOMEM; 118 119 out: 120 device_del(f_dev); 121 err_put_dev: 122 put_device(f_dev); 123 return retval; 124 } 125 126 static int fw_load_from_user_helper(struct firmware *firmware, 127 const char *name, struct device *device, 128 u32 opt_flags) 129 { 130 struct fw_sysfs *fw_sysfs; 131 long timeout; 132 int ret; 133 134 timeout = firmware_loading_timeout(); 135 if (opt_flags & FW_OPT_NOWAIT) { 136 timeout = usermodehelper_read_lock_wait(timeout); 137 if (!timeout) { 138 dev_dbg(device, "firmware: %s loading timed out\n", 139 name); 140 return -EBUSY; 141 } 142 } else { 143 ret = usermodehelper_read_trylock(); 144 if (WARN_ON(ret)) { 145 dev_err(device, "firmware: %s will not be loaded\n", 146 name); 147 return ret; 148 } 149 } 150 151 fw_sysfs = fw_create_instance(firmware, name, device, opt_flags); 152 if (IS_ERR(fw_sysfs)) { 153 ret = PTR_ERR(fw_sysfs); 154 goto out_unlock; 155 } 156 157 fw_sysfs->fw_priv = firmware->priv; 158 ret = fw_load_sysfs_fallback(fw_sysfs, timeout); 159 160 if (!ret) 161 ret = assign_fw(firmware, device); 162 163 out_unlock: 164 usermodehelper_read_unlock(); 165 166 return ret; 167 } 168 169 static bool fw_force_sysfs_fallback(u32 opt_flags) 170 { 171 if (fw_fallback_config.force_sysfs_fallback) 172 return true; 173 if (!(opt_flags & FW_OPT_USERHELPER)) 174 return false; 175 return true; 176 } 177 178 static bool fw_run_sysfs_fallback(u32 opt_flags) 179 { 180 int ret; 181 182 if (fw_fallback_config.ignore_sysfs_fallback) { 183 pr_info_once("Ignoring firmware sysfs fallback due to sysctl knob\n"); 184 return false; 185 } 186 187 if ((opt_flags & FW_OPT_NOFALLBACK_SYSFS)) 188 return false; 189 190 /* Also permit LSMs and IMA to fail firmware sysfs fallback */ 191 ret = security_kernel_load_data(LOADING_FIRMWARE, true); 192 if (ret < 0) 193 return false; 194 195 return fw_force_sysfs_fallback(opt_flags); 196 } 197 198 /** 199 * firmware_fallback_sysfs() - use the fallback mechanism to find firmware 200 * @fw: pointer to firmware image 201 * @name: name of firmware file to look for 202 * @device: device for which firmware is being loaded 203 * @opt_flags: options to control firmware loading behaviour, as defined by 204 * &enum fw_opt 205 * @ret: return value from direct lookup which triggered the fallback mechanism 206 * 207 * This function is called if direct lookup for the firmware failed, it enables 208 * a fallback mechanism through userspace by exposing a sysfs loading 209 * interface. Userspace is in charge of loading the firmware through the sysfs 210 * loading interface. This sysfs fallback mechanism may be disabled completely 211 * on a system by setting the proc sysctl value ignore_sysfs_fallback to true. 212 * If this is false we check if the internal API caller set the 213 * @FW_OPT_NOFALLBACK_SYSFS flag, if so it would also disable the fallback 214 * mechanism. A system may want to enforce the sysfs fallback mechanism at all 215 * times, it can do this by setting ignore_sysfs_fallback to false and 216 * force_sysfs_fallback to true. 217 * Enabling force_sysfs_fallback is functionally equivalent to build a kernel 218 * with CONFIG_FW_LOADER_USER_HELPER_FALLBACK. 219 **/ 220 int firmware_fallback_sysfs(struct firmware *fw, const char *name, 221 struct device *device, 222 u32 opt_flags, 223 int ret) 224 { 225 if (!fw_run_sysfs_fallback(opt_flags)) 226 return ret; 227 228 if (!(opt_flags & FW_OPT_NO_WARN)) 229 dev_warn(device, "Falling back to sysfs fallback for: %s\n", 230 name); 231 else 232 dev_dbg(device, "Falling back to sysfs fallback for: %s\n", 233 name); 234 return fw_load_from_user_helper(fw, name, device, opt_flags); 235 } 236