xref: /openbmc/linux/fs/proc/fd.c (revision b34e08d5)
1 #include <linux/sched.h>
2 #include <linux/errno.h>
3 #include <linux/dcache.h>
4 #include <linux/path.h>
5 #include <linux/fdtable.h>
6 #include <linux/namei.h>
7 #include <linux/pid.h>
8 #include <linux/security.h>
9 #include <linux/file.h>
10 #include <linux/seq_file.h>
11 
12 #include <linux/proc_fs.h>
13 
14 #include "../mount.h"
15 #include "internal.h"
16 #include "fd.h"
17 
18 static int seq_show(struct seq_file *m, void *v)
19 {
20 	struct files_struct *files = NULL;
21 	int f_flags = 0, ret = -ENOENT;
22 	struct file *file = NULL;
23 	struct task_struct *task;
24 
25 	task = get_proc_task(m->private);
26 	if (!task)
27 		return -ENOENT;
28 
29 	files = get_files_struct(task);
30 	put_task_struct(task);
31 
32 	if (files) {
33 		int fd = proc_fd(m->private);
34 
35 		spin_lock(&files->file_lock);
36 		file = fcheck_files(files, fd);
37 		if (file) {
38 			struct fdtable *fdt = files_fdtable(files);
39 
40 			f_flags = file->f_flags;
41 			if (close_on_exec(fd, fdt))
42 				f_flags |= O_CLOEXEC;
43 
44 			get_file(file);
45 			ret = 0;
46 		}
47 		spin_unlock(&files->file_lock);
48 		put_files_struct(files);
49 	}
50 
51 	if (!ret) {
52 		seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
53 			   (long long)file->f_pos, f_flags,
54 			   real_mount(file->f_path.mnt)->mnt_id);
55 		if (file->f_op->show_fdinfo)
56 			ret = file->f_op->show_fdinfo(m, file);
57 		fput(file);
58 	}
59 
60 	return ret;
61 }
62 
63 static int seq_fdinfo_open(struct inode *inode, struct file *file)
64 {
65 	return single_open(file, seq_show, inode);
66 }
67 
68 static const struct file_operations proc_fdinfo_file_operations = {
69 	.open		= seq_fdinfo_open,
70 	.read		= seq_read,
71 	.llseek		= seq_lseek,
72 	.release	= single_release,
73 };
74 
75 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
76 {
77 	struct files_struct *files;
78 	struct task_struct *task;
79 	const struct cred *cred;
80 	struct inode *inode;
81 	int fd;
82 
83 	if (flags & LOOKUP_RCU)
84 		return -ECHILD;
85 
86 	inode = dentry->d_inode;
87 	task = get_proc_task(inode);
88 	fd = proc_fd(inode);
89 
90 	if (task) {
91 		files = get_files_struct(task);
92 		if (files) {
93 			struct file *file;
94 
95 			rcu_read_lock();
96 			file = fcheck_files(files, fd);
97 			if (file) {
98 				unsigned f_mode = file->f_mode;
99 
100 				rcu_read_unlock();
101 				put_files_struct(files);
102 
103 				if (task_dumpable(task)) {
104 					rcu_read_lock();
105 					cred = __task_cred(task);
106 					inode->i_uid = cred->euid;
107 					inode->i_gid = cred->egid;
108 					rcu_read_unlock();
109 				} else {
110 					inode->i_uid = GLOBAL_ROOT_UID;
111 					inode->i_gid = GLOBAL_ROOT_GID;
112 				}
113 
114 				if (S_ISLNK(inode->i_mode)) {
115 					unsigned i_mode = S_IFLNK;
116 					if (f_mode & FMODE_READ)
117 						i_mode |= S_IRUSR | S_IXUSR;
118 					if (f_mode & FMODE_WRITE)
119 						i_mode |= S_IWUSR | S_IXUSR;
120 					inode->i_mode = i_mode;
121 				}
122 
123 				security_task_to_inode(task, inode);
124 				put_task_struct(task);
125 				return 1;
126 			}
127 			rcu_read_unlock();
128 			put_files_struct(files);
129 		}
130 		put_task_struct(task);
131 	}
132 
133 	d_drop(dentry);
134 	return 0;
135 }
136 
137 static const struct dentry_operations tid_fd_dentry_operations = {
138 	.d_revalidate	= tid_fd_revalidate,
139 	.d_delete	= pid_delete_dentry,
140 };
141 
142 static int proc_fd_link(struct dentry *dentry, struct path *path)
143 {
144 	struct files_struct *files = NULL;
145 	struct task_struct *task;
146 	int ret = -ENOENT;
147 
148 	task = get_proc_task(dentry->d_inode);
149 	if (task) {
150 		files = get_files_struct(task);
151 		put_task_struct(task);
152 	}
153 
154 	if (files) {
155 		int fd = proc_fd(dentry->d_inode);
156 		struct file *fd_file;
157 
158 		spin_lock(&files->file_lock);
159 		fd_file = fcheck_files(files, fd);
160 		if (fd_file) {
161 			*path = fd_file->f_path;
162 			path_get(&fd_file->f_path);
163 			ret = 0;
164 		}
165 		spin_unlock(&files->file_lock);
166 		put_files_struct(files);
167 	}
168 
169 	return ret;
170 }
171 
172 static int
173 proc_fd_instantiate(struct inode *dir, struct dentry *dentry,
174 		    struct task_struct *task, const void *ptr)
175 {
176 	unsigned fd = (unsigned long)ptr;
177 	struct proc_inode *ei;
178 	struct inode *inode;
179 
180 	inode = proc_pid_make_inode(dir->i_sb, task);
181 	if (!inode)
182 		goto out;
183 
184 	ei = PROC_I(inode);
185 	ei->fd = fd;
186 
187 	inode->i_mode = S_IFLNK;
188 	inode->i_op = &proc_pid_link_inode_operations;
189 	inode->i_size = 64;
190 
191 	ei->op.proc_get_link = proc_fd_link;
192 
193 	d_set_d_op(dentry, &tid_fd_dentry_operations);
194 	d_add(dentry, inode);
195 
196 	/* Close the race of the process dying before we return the dentry */
197 	if (tid_fd_revalidate(dentry, 0))
198 		return 0;
199  out:
200 	return -ENOENT;
201 }
202 
203 static struct dentry *proc_lookupfd_common(struct inode *dir,
204 					   struct dentry *dentry,
205 					   instantiate_t instantiate)
206 {
207 	struct task_struct *task = get_proc_task(dir);
208 	int result = -ENOENT;
209 	unsigned fd = name_to_int(dentry);
210 
211 	if (!task)
212 		goto out_no_task;
213 	if (fd == ~0U)
214 		goto out;
215 
216 	result = instantiate(dir, dentry, task, (void *)(unsigned long)fd);
217 out:
218 	put_task_struct(task);
219 out_no_task:
220 	return ERR_PTR(result);
221 }
222 
223 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
224 			      instantiate_t instantiate)
225 {
226 	struct task_struct *p = get_proc_task(file_inode(file));
227 	struct files_struct *files;
228 	unsigned int fd;
229 
230 	if (!p)
231 		return -ENOENT;
232 
233 	if (!dir_emit_dots(file, ctx))
234 		goto out;
235 	files = get_files_struct(p);
236 	if (!files)
237 		goto out;
238 
239 	rcu_read_lock();
240 	for (fd = ctx->pos - 2;
241 	     fd < files_fdtable(files)->max_fds;
242 	     fd++, ctx->pos++) {
243 		char name[PROC_NUMBUF];
244 		int len;
245 
246 		if (!fcheck_files(files, fd))
247 			continue;
248 		rcu_read_unlock();
249 
250 		len = snprintf(name, sizeof(name), "%d", fd);
251 		if (!proc_fill_cache(file, ctx,
252 				     name, len, instantiate, p,
253 				     (void *)(unsigned long)fd))
254 			goto out_fd_loop;
255 		rcu_read_lock();
256 	}
257 	rcu_read_unlock();
258 out_fd_loop:
259 	put_files_struct(files);
260 out:
261 	put_task_struct(p);
262 	return 0;
263 }
264 
265 static int proc_readfd(struct file *file, struct dir_context *ctx)
266 {
267 	return proc_readfd_common(file, ctx, proc_fd_instantiate);
268 }
269 
270 const struct file_operations proc_fd_operations = {
271 	.read		= generic_read_dir,
272 	.iterate	= proc_readfd,
273 	.llseek		= default_llseek,
274 };
275 
276 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
277 				    unsigned int flags)
278 {
279 	return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
280 }
281 
282 /*
283  * /proc/pid/fd needs a special permission handler so that a process can still
284  * access /proc/self/fd after it has executed a setuid().
285  */
286 int proc_fd_permission(struct inode *inode, int mask)
287 {
288 	int rv = generic_permission(inode, mask);
289 	if (rv == 0)
290 		return 0;
291 	if (task_tgid(current) == proc_pid(inode))
292 		rv = 0;
293 	return rv;
294 }
295 
296 const struct inode_operations proc_fd_inode_operations = {
297 	.lookup		= proc_lookupfd,
298 	.permission	= proc_fd_permission,
299 	.setattr	= proc_setattr,
300 };
301 
302 static int
303 proc_fdinfo_instantiate(struct inode *dir, struct dentry *dentry,
304 			struct task_struct *task, const void *ptr)
305 {
306 	unsigned fd = (unsigned long)ptr;
307 	struct proc_inode *ei;
308 	struct inode *inode;
309 
310 	inode = proc_pid_make_inode(dir->i_sb, task);
311 	if (!inode)
312 		goto out;
313 
314 	ei = PROC_I(inode);
315 	ei->fd = fd;
316 
317 	inode->i_mode = S_IFREG | S_IRUSR;
318 	inode->i_fop = &proc_fdinfo_file_operations;
319 
320 	d_set_d_op(dentry, &tid_fd_dentry_operations);
321 	d_add(dentry, inode);
322 
323 	/* Close the race of the process dying before we return the dentry */
324 	if (tid_fd_revalidate(dentry, 0))
325 		return 0;
326  out:
327 	return -ENOENT;
328 }
329 
330 static struct dentry *
331 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
332 {
333 	return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
334 }
335 
336 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
337 {
338 	return proc_readfd_common(file, ctx,
339 				  proc_fdinfo_instantiate);
340 }
341 
342 const struct inode_operations proc_fdinfo_inode_operations = {
343 	.lookup		= proc_lookupfdinfo,
344 	.setattr	= proc_setattr,
345 };
346 
347 const struct file_operations proc_fdinfo_operations = {
348 	.read		= generic_read_dir,
349 	.iterate	= proc_readfdinfo,
350 	.llseek		= default_llseek,
351 };
352