xref: /openbmc/linux/fs/proc/fd.c (revision 6774def6)
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 	return 0;
133 }
134 
135 static const struct dentry_operations tid_fd_dentry_operations = {
136 	.d_revalidate	= tid_fd_revalidate,
137 	.d_delete	= pid_delete_dentry,
138 };
139 
140 static int proc_fd_link(struct dentry *dentry, struct path *path)
141 {
142 	struct files_struct *files = NULL;
143 	struct task_struct *task;
144 	int ret = -ENOENT;
145 
146 	task = get_proc_task(dentry->d_inode);
147 	if (task) {
148 		files = get_files_struct(task);
149 		put_task_struct(task);
150 	}
151 
152 	if (files) {
153 		int fd = proc_fd(dentry->d_inode);
154 		struct file *fd_file;
155 
156 		spin_lock(&files->file_lock);
157 		fd_file = fcheck_files(files, fd);
158 		if (fd_file) {
159 			*path = fd_file->f_path;
160 			path_get(&fd_file->f_path);
161 			ret = 0;
162 		}
163 		spin_unlock(&files->file_lock);
164 		put_files_struct(files);
165 	}
166 
167 	return ret;
168 }
169 
170 static int
171 proc_fd_instantiate(struct inode *dir, struct dentry *dentry,
172 		    struct task_struct *task, const void *ptr)
173 {
174 	unsigned fd = (unsigned long)ptr;
175 	struct proc_inode *ei;
176 	struct inode *inode;
177 
178 	inode = proc_pid_make_inode(dir->i_sb, task);
179 	if (!inode)
180 		goto out;
181 
182 	ei = PROC_I(inode);
183 	ei->fd = fd;
184 
185 	inode->i_mode = S_IFLNK;
186 	inode->i_op = &proc_pid_link_inode_operations;
187 	inode->i_size = 64;
188 
189 	ei->op.proc_get_link = proc_fd_link;
190 
191 	d_set_d_op(dentry, &tid_fd_dentry_operations);
192 	d_add(dentry, inode);
193 
194 	/* Close the race of the process dying before we return the dentry */
195 	if (tid_fd_revalidate(dentry, 0))
196 		return 0;
197  out:
198 	return -ENOENT;
199 }
200 
201 static struct dentry *proc_lookupfd_common(struct inode *dir,
202 					   struct dentry *dentry,
203 					   instantiate_t instantiate)
204 {
205 	struct task_struct *task = get_proc_task(dir);
206 	int result = -ENOENT;
207 	unsigned fd = name_to_int(&dentry->d_name);
208 
209 	if (!task)
210 		goto out_no_task;
211 	if (fd == ~0U)
212 		goto out;
213 
214 	result = instantiate(dir, dentry, task, (void *)(unsigned long)fd);
215 out:
216 	put_task_struct(task);
217 out_no_task:
218 	return ERR_PTR(result);
219 }
220 
221 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
222 			      instantiate_t instantiate)
223 {
224 	struct task_struct *p = get_proc_task(file_inode(file));
225 	struct files_struct *files;
226 	unsigned int fd;
227 
228 	if (!p)
229 		return -ENOENT;
230 
231 	if (!dir_emit_dots(file, ctx))
232 		goto out;
233 	files = get_files_struct(p);
234 	if (!files)
235 		goto out;
236 
237 	rcu_read_lock();
238 	for (fd = ctx->pos - 2;
239 	     fd < files_fdtable(files)->max_fds;
240 	     fd++, ctx->pos++) {
241 		char name[PROC_NUMBUF];
242 		int len;
243 
244 		if (!fcheck_files(files, fd))
245 			continue;
246 		rcu_read_unlock();
247 
248 		len = snprintf(name, sizeof(name), "%d", fd);
249 		if (!proc_fill_cache(file, ctx,
250 				     name, len, instantiate, p,
251 				     (void *)(unsigned long)fd))
252 			goto out_fd_loop;
253 		rcu_read_lock();
254 	}
255 	rcu_read_unlock();
256 out_fd_loop:
257 	put_files_struct(files);
258 out:
259 	put_task_struct(p);
260 	return 0;
261 }
262 
263 static int proc_readfd(struct file *file, struct dir_context *ctx)
264 {
265 	return proc_readfd_common(file, ctx, proc_fd_instantiate);
266 }
267 
268 const struct file_operations proc_fd_operations = {
269 	.read		= generic_read_dir,
270 	.iterate	= proc_readfd,
271 	.llseek		= default_llseek,
272 };
273 
274 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
275 				    unsigned int flags)
276 {
277 	return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
278 }
279 
280 /*
281  * /proc/pid/fd needs a special permission handler so that a process can still
282  * access /proc/self/fd after it has executed a setuid().
283  */
284 int proc_fd_permission(struct inode *inode, int mask)
285 {
286 	int rv = generic_permission(inode, mask);
287 	if (rv == 0)
288 		return 0;
289 	if (task_tgid(current) == proc_pid(inode))
290 		rv = 0;
291 	return rv;
292 }
293 
294 const struct inode_operations proc_fd_inode_operations = {
295 	.lookup		= proc_lookupfd,
296 	.permission	= proc_fd_permission,
297 	.setattr	= proc_setattr,
298 };
299 
300 static int
301 proc_fdinfo_instantiate(struct inode *dir, struct dentry *dentry,
302 			struct task_struct *task, const void *ptr)
303 {
304 	unsigned fd = (unsigned long)ptr;
305 	struct proc_inode *ei;
306 	struct inode *inode;
307 
308 	inode = proc_pid_make_inode(dir->i_sb, task);
309 	if (!inode)
310 		goto out;
311 
312 	ei = PROC_I(inode);
313 	ei->fd = fd;
314 
315 	inode->i_mode = S_IFREG | S_IRUSR;
316 	inode->i_fop = &proc_fdinfo_file_operations;
317 
318 	d_set_d_op(dentry, &tid_fd_dentry_operations);
319 	d_add(dentry, inode);
320 
321 	/* Close the race of the process dying before we return the dentry */
322 	if (tid_fd_revalidate(dentry, 0))
323 		return 0;
324  out:
325 	return -ENOENT;
326 }
327 
328 static struct dentry *
329 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
330 {
331 	return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
332 }
333 
334 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
335 {
336 	return proc_readfd_common(file, ctx,
337 				  proc_fdinfo_instantiate);
338 }
339 
340 const struct inode_operations proc_fdinfo_inode_operations = {
341 	.lookup		= proc_lookupfdinfo,
342 	.setattr	= proc_setattr,
343 };
344 
345 const struct file_operations proc_fdinfo_operations = {
346 	.read		= generic_read_dir,
347 	.iterate	= proc_readfdinfo,
348 	.llseek		= default_llseek,
349 };
350