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  */
fw_fallback_set_cache_timeout(void)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 */
fw_fallback_set_default_timeout(void)31 void fw_fallback_set_default_timeout(void)
32 {
33 	__fw_fallback_set_timeout(fw_fallback_config.old_timeout);
34 }
35 
firmware_loading_timeout(void)36 static long firmware_loading_timeout(void)
37 {
38 	return __firmware_loading_timeout() > 0 ?
39 		__firmware_loading_timeout() * HZ : MAX_JIFFY_OFFSET;
40 }
41 
fw_sysfs_wait_timeout(struct fw_priv * fw_priv,long timeout)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 
kill_pending_fw_fallback_reqs(bool only_kill_custom)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  **/
fw_load_sysfs_fallback(struct fw_sysfs * fw_sysfs,long timeout)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 
fw_load_from_user_helper(struct firmware * firmware,const char * name,struct device * device,u32 opt_flags)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 
fw_force_sysfs_fallback(u32 opt_flags)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 
fw_run_sysfs_fallback(u32 opt_flags)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  **/
firmware_fallback_sysfs(struct firmware * fw,const char * name,struct device * device,u32 opt_flags,int ret)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