1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/sched/signal.h>
3 #include <linux/errno.h>
4 #include <linux/dcache.h>
5 #include <linux/path.h>
6 #include <linux/fdtable.h>
7 #include <linux/namei.h>
8 #include <linux/pid.h>
9 #include <linux/security.h>
10 #include <linux/file.h>
11 #include <linux/seq_file.h>
12 #include <linux/fs.h>
13
14 #include <linux/proc_fs.h>
15
16 #include "../mount.h"
17 #include "internal.h"
18 #include "fd.h"
19
seq_show(struct seq_file * m,void * v)20 static int seq_show(struct seq_file *m, void *v)
21 {
22 struct files_struct *files = NULL;
23 int f_flags = 0, ret = -ENOENT;
24 struct file *file = NULL;
25 struct task_struct *task;
26
27 task = get_proc_task(m->private);
28 if (!task)
29 return -ENOENT;
30
31 files = get_files_struct(task);
32 put_task_struct(task);
33
34 if (files) {
35 unsigned int fd = proc_fd(m->private);
36
37 spin_lock(&files->file_lock);
38 file = fcheck_files(files, fd);
39 if (file) {
40 struct fdtable *fdt = files_fdtable(files);
41
42 f_flags = file->f_flags;
43 if (close_on_exec(fd, fdt))
44 f_flags |= O_CLOEXEC;
45
46 get_file(file);
47 ret = 0;
48 }
49 spin_unlock(&files->file_lock);
50 put_files_struct(files);
51 }
52
53 if (ret)
54 return ret;
55
56 seq_printf(m, "pos:\t%lli\nflags:\t0%o\nmnt_id:\t%i\n",
57 (long long)file->f_pos, f_flags,
58 real_mount(file->f_path.mnt)->mnt_id);
59
60 show_fd_locks(m, file, files);
61 if (seq_has_overflowed(m))
62 goto out;
63
64 if (file->f_op->show_fdinfo)
65 file->f_op->show_fdinfo(m, file);
66
67 out:
68 fput(file);
69 return 0;
70 }
71
seq_fdinfo_open(struct inode * inode,struct file * file)72 static int seq_fdinfo_open(struct inode *inode, struct file *file)
73 {
74 return single_open(file, seq_show, inode);
75 }
76
77 static const struct file_operations proc_fdinfo_file_operations = {
78 .open = seq_fdinfo_open,
79 .read = seq_read,
80 .llseek = seq_lseek,
81 .release = single_release,
82 };
83
tid_fd_mode(struct task_struct * task,unsigned fd,fmode_t * mode)84 static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
85 {
86 struct files_struct *files = get_files_struct(task);
87 struct file *file;
88
89 if (!files)
90 return false;
91
92 rcu_read_lock();
93 file = fcheck_files(files, fd);
94 if (file)
95 *mode = file->f_mode;
96 rcu_read_unlock();
97 put_files_struct(files);
98 return !!file;
99 }
100
tid_fd_update_inode(struct task_struct * task,struct inode * inode,fmode_t f_mode)101 static void tid_fd_update_inode(struct task_struct *task, struct inode *inode,
102 fmode_t f_mode)
103 {
104 task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
105
106 if (S_ISLNK(inode->i_mode)) {
107 unsigned i_mode = S_IFLNK;
108 if (f_mode & FMODE_READ)
109 i_mode |= S_IRUSR | S_IXUSR;
110 if (f_mode & FMODE_WRITE)
111 i_mode |= S_IWUSR | S_IXUSR;
112 inode->i_mode = i_mode;
113 }
114 security_task_to_inode(task, inode);
115 }
116
tid_fd_revalidate(struct dentry * dentry,unsigned int flags)117 static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
118 {
119 struct task_struct *task;
120 struct inode *inode;
121 unsigned int fd;
122
123 if (flags & LOOKUP_RCU)
124 return -ECHILD;
125
126 inode = d_inode(dentry);
127 task = get_proc_task(inode);
128 fd = proc_fd(inode);
129
130 if (task) {
131 fmode_t f_mode;
132 if (tid_fd_mode(task, fd, &f_mode)) {
133 tid_fd_update_inode(task, inode, f_mode);
134 put_task_struct(task);
135 return 1;
136 }
137 put_task_struct(task);
138 }
139 return 0;
140 }
141
142 static const struct dentry_operations tid_fd_dentry_operations = {
143 .d_revalidate = tid_fd_revalidate,
144 .d_delete = pid_delete_dentry,
145 };
146
proc_fd_link(struct dentry * dentry,struct path * path)147 static int proc_fd_link(struct dentry *dentry, struct path *path)
148 {
149 struct files_struct *files = NULL;
150 struct task_struct *task;
151 int ret = -ENOENT;
152
153 task = get_proc_task(d_inode(dentry));
154 if (task) {
155 files = get_files_struct(task);
156 put_task_struct(task);
157 }
158
159 if (files) {
160 unsigned int fd = proc_fd(d_inode(dentry));
161 struct file *fd_file;
162
163 spin_lock(&files->file_lock);
164 fd_file = fcheck_files(files, fd);
165 if (fd_file) {
166 *path = fd_file->f_path;
167 path_get(&fd_file->f_path);
168 ret = 0;
169 }
170 spin_unlock(&files->file_lock);
171 put_files_struct(files);
172 }
173
174 return ret;
175 }
176
177 struct fd_data {
178 fmode_t mode;
179 unsigned fd;
180 };
181
proc_fd_instantiate(struct dentry * dentry,struct task_struct * task,const void * ptr)182 static struct dentry *proc_fd_instantiate(struct dentry *dentry,
183 struct task_struct *task, const void *ptr)
184 {
185 const struct fd_data *data = ptr;
186 struct proc_inode *ei;
187 struct inode *inode;
188
189 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFLNK);
190 if (!inode)
191 return ERR_PTR(-ENOENT);
192
193 ei = PROC_I(inode);
194 ei->fd = data->fd;
195
196 inode->i_op = &proc_pid_link_inode_operations;
197 inode->i_size = 64;
198
199 ei->op.proc_get_link = proc_fd_link;
200 tid_fd_update_inode(task, inode, data->mode);
201
202 d_set_d_op(dentry, &tid_fd_dentry_operations);
203 return d_splice_alias(inode, dentry);
204 }
205
proc_lookupfd_common(struct inode * dir,struct dentry * dentry,instantiate_t instantiate)206 static struct dentry *proc_lookupfd_common(struct inode *dir,
207 struct dentry *dentry,
208 instantiate_t instantiate)
209 {
210 struct task_struct *task = get_proc_task(dir);
211 struct fd_data data = {.fd = name_to_int(&dentry->d_name)};
212 struct dentry *result = ERR_PTR(-ENOENT);
213
214 if (!task)
215 goto out_no_task;
216 if (data.fd == ~0U)
217 goto out;
218 if (!tid_fd_mode(task, data.fd, &data.mode))
219 goto out;
220
221 result = instantiate(dentry, task, &data);
222 out:
223 put_task_struct(task);
224 out_no_task:
225 return result;
226 }
227
proc_readfd_common(struct file * file,struct dir_context * ctx,instantiate_t instantiate)228 static int proc_readfd_common(struct file *file, struct dir_context *ctx,
229 instantiate_t instantiate)
230 {
231 struct task_struct *p = get_proc_task(file_inode(file));
232 struct files_struct *files;
233 unsigned int fd;
234
235 if (!p)
236 return -ENOENT;
237
238 if (!dir_emit_dots(file, ctx))
239 goto out;
240 files = get_files_struct(p);
241 if (!files)
242 goto out;
243
244 rcu_read_lock();
245 for (fd = ctx->pos - 2;
246 fd < files_fdtable(files)->max_fds;
247 fd++, ctx->pos++) {
248 struct file *f;
249 struct fd_data data;
250 char name[10 + 1];
251 unsigned int len;
252
253 f = fcheck_files(files, fd);
254 if (!f)
255 continue;
256 data.mode = f->f_mode;
257 rcu_read_unlock();
258 data.fd = fd;
259
260 len = snprintf(name, sizeof(name), "%u", fd);
261 if (!proc_fill_cache(file, ctx,
262 name, len, instantiate, p,
263 &data))
264 goto out_fd_loop;
265 cond_resched();
266 rcu_read_lock();
267 }
268 rcu_read_unlock();
269 out_fd_loop:
270 put_files_struct(files);
271 out:
272 put_task_struct(p);
273 return 0;
274 }
275
proc_readfd(struct file * file,struct dir_context * ctx)276 static int proc_readfd(struct file *file, struct dir_context *ctx)
277 {
278 return proc_readfd_common(file, ctx, proc_fd_instantiate);
279 }
280
281 const struct file_operations proc_fd_operations = {
282 .read = generic_read_dir,
283 .iterate_shared = proc_readfd,
284 .llseek = generic_file_llseek,
285 };
286
proc_lookupfd(struct inode * dir,struct dentry * dentry,unsigned int flags)287 static struct dentry *proc_lookupfd(struct inode *dir, struct dentry *dentry,
288 unsigned int flags)
289 {
290 return proc_lookupfd_common(dir, dentry, proc_fd_instantiate);
291 }
292
293 /*
294 * /proc/pid/fd needs a special permission handler so that a process can still
295 * access /proc/self/fd after it has executed a setuid().
296 */
proc_fd_permission(struct inode * inode,int mask)297 int proc_fd_permission(struct inode *inode, int mask)
298 {
299 struct task_struct *p;
300 int rv;
301
302 rv = generic_permission(inode, mask);
303 if (rv == 0)
304 return rv;
305
306 rcu_read_lock();
307 p = pid_task(proc_pid(inode), PIDTYPE_PID);
308 if (p && same_thread_group(p, current))
309 rv = 0;
310 rcu_read_unlock();
311
312 return rv;
313 }
314
315 const struct inode_operations proc_fd_inode_operations = {
316 .lookup = proc_lookupfd,
317 .permission = proc_fd_permission,
318 .setattr = proc_setattr,
319 };
320
proc_fdinfo_instantiate(struct dentry * dentry,struct task_struct * task,const void * ptr)321 static struct dentry *proc_fdinfo_instantiate(struct dentry *dentry,
322 struct task_struct *task, const void *ptr)
323 {
324 const struct fd_data *data = ptr;
325 struct proc_inode *ei;
326 struct inode *inode;
327
328 inode = proc_pid_make_inode(dentry->d_sb, task, S_IFREG | S_IRUSR);
329 if (!inode)
330 return ERR_PTR(-ENOENT);
331
332 ei = PROC_I(inode);
333 ei->fd = data->fd;
334
335 inode->i_fop = &proc_fdinfo_file_operations;
336 tid_fd_update_inode(task, inode, 0);
337
338 d_set_d_op(dentry, &tid_fd_dentry_operations);
339 return d_splice_alias(inode, dentry);
340 }
341
342 static struct dentry *
proc_lookupfdinfo(struct inode * dir,struct dentry * dentry,unsigned int flags)343 proc_lookupfdinfo(struct inode *dir, struct dentry *dentry, unsigned int flags)
344 {
345 return proc_lookupfd_common(dir, dentry, proc_fdinfo_instantiate);
346 }
347
proc_readfdinfo(struct file * file,struct dir_context * ctx)348 static int proc_readfdinfo(struct file *file, struct dir_context *ctx)
349 {
350 return proc_readfd_common(file, ctx,
351 proc_fdinfo_instantiate);
352 }
353
354 const struct inode_operations proc_fdinfo_inode_operations = {
355 .lookup = proc_lookupfdinfo,
356 .setattr = proc_setattr,
357 };
358
359 const struct file_operations proc_fdinfo_operations = {
360 .read = generic_read_dir,
361 .iterate_shared = proc_readfdinfo,
362 .llseek = generic_file_llseek,
363 };
364