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2024-05-16 8d2a02b24d66aa359e83eebc1ed3c0f85367a1cb

 kernel/fs/seq_file.c
..
..
@@ -6,6 +6,8 @@
6
6
  * initial implementation -- AV, Oct 2001.
7
7
  */
8
8
 
9
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10
+
9
11
 #include <linux/cache.h>
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12
 #include <linux/fs.h>
11
13
 #include <linux/export.h>
..
..
@@ -16,6 +18,7 @@
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18
 #include <linux/mm.h>
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19
 #include <linux/printk.h>
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20
 #include <linux/string_helpers.h>
21
+#include <linux/uio.h>
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22
 
20
23
 #include <linux/uaccess.h>
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24
 #include <asm/page.h>
..
..
@@ -71,13 +74,6 @@
71
74
 	p->file = file;
72
75
 
73
76
 	/*
74
-	 * Wrappers around seq_open(e.g. swaps_open) need to be
75
-	 * aware of this. If they set f_version themselves, they
76
-	 * should call seq_open first and then set f_version.
77
-	 */
78
-	file->f_version = 0;
79
-
80
-	/*
81
77
 	 * seq_files support lseek() and pread().  They do not implement
82
78
 	 * write() at all, but we clear FMODE_PWRITE here for historical
83
79
 	 * reasons.
..
..
@@ -97,7 +93,6 @@
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93
 	int error = 0;
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94
 	void *p;
99
95
 
100
-	m->version = 0;
101
96
 	m->index = 0;
102
97
 	m->count = m->from = 0;
103
98
 	if (!offset)
..
..
@@ -155,50 +150,58 @@
155
150
  */
156
151
 ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
157
152
 {
158
-	struct seq_file *m = file->private_data;
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+	struct iovec iov = { .iov_base = buf, .iov_len = size};
154
+	struct kiocb kiocb;
155
+	struct iov_iter iter;
156
+	ssize_t ret;
157
+
158
+	init_sync_kiocb(&kiocb, file);
159
+	iov_iter_init(&iter, READ, &iov, 1, size);
160
+
161
+	kiocb.ki_pos = *ppos;
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+	ret = seq_read_iter(&kiocb, &iter);
163
+	*ppos = kiocb.ki_pos;
164
+	return ret;
165
+}
166
+EXPORT_SYMBOL(seq_read);
167
+
168
+/*
169
+ * Ready-made ->f_op->read_iter()
170
+ */
171
+ssize_t seq_read_iter(struct kiocb *iocb, struct iov_iter *iter)
172
+{
173
+	struct seq_file *m = iocb->ki_filp->private_data;
159
174
 	size_t copied = 0;
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175
 	size_t n;
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176
 	void *p;
162
177
 	int err = 0;
163
178
 
164
-	mutex_lock(&m->lock);
179
+	if (!iov_iter_count(iter))
180
+		return 0;
165
181
 
166
-	/*
167
-	 * seq_file->op->..m_start/m_stop/m_next may do special actions
168
-	 * or optimisations based on the file->f_version, so we want to
169
-	 * pass the file->f_version to those methods.
170
-	 *
171
-	 * seq_file->version is just copy of f_version, and seq_file
172
-	 * methods can treat it simply as file version.
173
-	 * It is copied in first and copied out after all operations.
174
-	 * It is convenient to have it as  part of structure to avoid the
175
-	 * need of passing another argument to all the seq_file methods.
176
-	 */
177
-	m->version = file->f_version;
182
+	mutex_lock(&m->lock);
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183
 
179
184
 	/*
180
185
 	 * if request is to read from zero offset, reset iterator to first
181
186
 	 * record as it might have been already advanced by previous requests
182
187
 	 */
183
-	if (*ppos == 0) {
188
+	if (iocb->ki_pos == 0) {
184
189
 		m->index = 0;
185
-		m->version = 0;
186
190
 		m->count = 0;
187
191
 	}
188
192
 
189
-	/* Don't assume *ppos is where we left it */
190
-	if (unlikely(*ppos != m->read_pos)) {
191
-		while ((err = traverse(m, *ppos)) == -EAGAIN)
193
+	/* Don't assume ki_pos is where we left it */
194
+	if (unlikely(iocb->ki_pos != m->read_pos)) {
195
+		while ((err = traverse(m, iocb->ki_pos)) == -EAGAIN)
192
196
 			;
193
197
 		if (err) {
194
198
 			/* With prejudice... */
195
199
 			m->read_pos = 0;
196
-			m->version = 0;
197
200
 			m->index = 0;
198
201
 			m->count = 0;
199
202
 			goto Done;
200
203
 		} else {
201
-			m->read_pos = *ppos;
204
+			m->read_pos = iocb->ki_pos;
202
205
 		}
203
206
 	}
204
207
 
..
..
@@ -208,99 +211,91 @@
208
211
 		if (!m->buf)
209
212
 			goto Enomem;
210
213
 	}
211
-	/* if not empty - flush it first */
214
+	// something left in the buffer - copy it out first
212
215
 	if (m->count) {
213
-		n = min(m->count, size);
214
-		err = copy_to_user(buf, m->buf + m->from, n);
215
-		if (err)
216
-			goto Efault;
216
+		n = copy_to_iter(m->buf + m->from, m->count, iter);
217
217
 		m->count -= n;
218
218
 		m->from += n;
219
-		size -= n;
220
-		buf += n;
221
219
 		copied += n;
222
-		if (!size)
220
+		if (m->count)	// hadn't managed to copy everything
223
221
 			goto Done;
224
222
 	}
225
-	/* we need at least one record in buffer */
223
+	// get a non-empty record in the buffer
226
224
 	m->from = 0;
227
225
 	p = m->op->start(m, &m->index);
228
226
 	while (1) {
229
227
 		err = PTR_ERR(p);
230
-		if (!p || IS_ERR(p))
228
+		if (!p || IS_ERR(p))	// EOF or an error
231
229
 			break;
232
230
 		err = m->op->show(m, p);
233
-		if (err < 0)
231
+		if (err < 0)		// hard error
234
232
 			break;
235
-		if (unlikely(err))
233
+		if (unlikely(err))	// ->show() says "skip it"
236
234
 			m->count = 0;
237
-		if (unlikely(!m->count)) {
235
+		if (unlikely(!m->count)) { // empty record
238
236
 			p = m->op->next(m, p, &m->index);
239
237
 			continue;
240
238
 		}
241
-		if (m->count < m->size)
239
+		if (!seq_has_overflowed(m)) // got it
242
240
 			goto Fill;
241
+		// need a bigger buffer
243
242
 		m->op->stop(m, p);
244
243
 		kvfree(m->buf);
245
244
 		m->count = 0;
246
245
 		m->buf = seq_buf_alloc(m->size <<= 1);
247
246
 		if (!m->buf)
248
247
 			goto Enomem;
249
-		m->version = 0;
250
248
 		p = m->op->start(m, &m->index);
251
249
 	}
250
+	// EOF or an error
252
251
 	m->op->stop(m, p);
253
252
 	m->count = 0;
254
253
 	goto Done;
255
254
 Fill:
256
-	/* they want more? let's try to get some more */
255
+	// one non-empty record is in the buffer; if they want more,
256
+	// try to fit more in, but in any case we need to advance
257
+	// the iterator once for every record shown.
257
258
 	while (1) {
258
259
 		size_t offs = m->count;
259
260
 		loff_t pos = m->index;
260
261
 
261
262
 		p = m->op->next(m, p, &m->index);
262
-		if (pos == m->index)
263
-			/* Buggy ->next function */
263
+		if (pos == m->index) {
264
+			pr_info_ratelimited("buggy .next function %ps did not update position index\n",
265
+					    m->op->next);
264
266
 			m->index++;
265
-		if (!p || IS_ERR(p)) {
266
-			err = PTR_ERR(p);
267
-			break;
268
267
 		}
269
-		if (m->count >= size)
268
+		if (!p || IS_ERR(p))	// no next record for us
269
+			break;
270
+		if (m->count >= iov_iter_count(iter))
270
271
 			break;
271
272
 		err = m->op->show(m, p);
272
-		if (seq_has_overflowed(m) || err) {
273
+		if (err > 0) {		// ->show() says "skip it"
273
274
 			m->count = offs;
274
-			if (likely(err <= 0))
275
-				break;
275
+		} else if (err || seq_has_overflowed(m)) {
276
+			m->count = offs;
277
+			break;
276
278
 		}
277
279
 	}
278
280
 	m->op->stop(m, p);
279
-	n = min(m->count, size);
280
-	err = copy_to_user(buf, m->buf, n);
281
-	if (err)
282
-		goto Efault;
281
+	n = copy_to_iter(m->buf, m->count, iter);
283
282
 	copied += n;
284
283
 	m->count -= n;
285
284
 	m->from = n;
286
285
 Done:
287
-	if (!copied)
288
-		copied = err;
289
-	else {
290
-		*ppos += copied;
286
+	if (unlikely(!copied)) {
287
+		copied = m->count ? -EFAULT : err;
288
+	} else {
289
+		iocb->ki_pos += copied;
291
290
 		m->read_pos += copied;
292
291
 	}
293
-	file->f_version = m->version;
294
292
 	mutex_unlock(&m->lock);
295
293
 	return copied;
296
294
 Enomem:
297
295
 	err = -ENOMEM;
298
296
 	goto Done;
299
-Efault:
300
-	err = -EFAULT;
301
-	goto Done;
302
297
 }
303
-EXPORT_SYMBOL(seq_read);
298
+EXPORT_SYMBOL(seq_read_iter);
304
299
 
305
300
 /**
306
301
  *	seq_lseek -	->llseek() method for sequential files.
..
..
@@ -316,10 +311,10 @@
316
311
 	loff_t retval = -EINVAL;
317
312
 
318
313
 	mutex_lock(&m->lock);
319
-	m->version = file->f_version;
320
314
 	switch (whence) {
321
315
 	case SEEK_CUR:
322
316
 		offset += file->f_pos;
317
+		fallthrough;
323
318
 	case SEEK_SET:
324
319
 		if (offset < 0)
325
320
 			break;
..
..
@@ -331,7 +326,6 @@
331
326
 				/* with extreme prejudice... */
332
327
 				file->f_pos = 0;
333
328
 				m->read_pos = 0;
334
-				m->version = 0;
335
329
 				m->index = 0;
336
330
 				m->count = 0;
337
331
 			} else {
..
..
@@ -342,7 +336,6 @@
342
336
 			file->f_pos = offset;
343
337
 		}
344
338
 	}
345
-	file->f_version = m->version;
346
339
 	mutex_unlock(&m->lock);
347
340
 	return retval;
348
341
 }
..
..
@@ -386,6 +379,17 @@
386
379
 }
387
380
 EXPORT_SYMBOL(seq_escape);
388
381
 
382
+void seq_escape_mem_ascii(struct seq_file *m, const char *src, size_t isz)
383
+{
384
+	char *buf;
385
+	size_t size = seq_get_buf(m, &buf);
386
+	int ret;
387
+
388
+	ret = string_escape_mem_ascii(src, isz, buf, size);
389
+	seq_commit(m, ret < size ? ret : -1);
390
+}
391
+EXPORT_SYMBOL(seq_escape_mem_ascii);
392
+
389
393
 void seq_vprintf(struct seq_file *m, const char *f, va_list args)
390
394
 {
391
395
 	int len;