1// SPDX-License-Identifier: GPL-2.0
2// Author: Kirill Smelkov (kirr@nexedi.com)
3//
4// Search for stream-like files that are using nonseekable_open and convert
5// them to stream_open. A stream-like file is a file that does not use ppos in
6// its read and write. Rationale for the conversion is to avoid deadlock in
7// between read and write.
8
9virtual report
10virtual patch
11virtual explain  // explain decisions in the patch (SPFLAGS="-D explain")
12
13// stream-like reader & writer - ones that do not depend on f_pos.
14@ stream_reader @
15identifier readstream, ppos;
16identifier f, buf, len;
17type loff_t;
18@@
19  ssize_t readstream(struct file *f, char *buf, size_t len, loff_t *ppos)
20  {
21    ... when != ppos
22  }
23
24@ stream_writer @
25identifier writestream, ppos;
26identifier f, buf, len;
27type loff_t;
28@@
29  ssize_t writestream(struct file *f, const char *buf, size_t len, loff_t *ppos)
30  {
31    ... when != ppos
32  }
33
34
35// a function that blocks
36@ blocks @
37identifier block_f;
38identifier wait_event =~ "^wait_event_.*";
39@@
40  block_f(...) {
41    ... when exists
42    wait_event(...)
43    ... when exists
44  }
45
46// stream_reader that can block inside.
47//
48// XXX wait_* can be called not directly from current function (e.g. func -> f -> g -> wait())
49// XXX currently reader_blocks supports only direct and 1-level indirect cases.
50@ reader_blocks_direct @
51identifier stream_reader.readstream;
52identifier wait_event =~ "^wait_event_.*";
53@@
54  readstream(...)
55  {
56    ... when exists
57    wait_event(...)
58    ... when exists
59  }
60
61@ reader_blocks_1 @
62identifier stream_reader.readstream;
63identifier blocks.block_f;
64@@
65  readstream(...)
66  {
67    ... when exists
68    block_f(...)
69    ... when exists
70  }
71
72@ reader_blocks depends on reader_blocks_direct || reader_blocks_1 @
73identifier stream_reader.readstream;
74@@
75  readstream(...) {
76    ...
77  }
78
79
80// file_operations + whether they have _any_ .read, .write, .llseek ... at all.
81//
82// XXX add support for file_operations xxx[N] = ...	(sound/core/pcm_native.c)
83@ fops0 @
84identifier fops;
85@@
86  struct file_operations fops = {
87    ...
88  };
89
90@ has_read @
91identifier fops0.fops;
92identifier read_f;
93@@
94  struct file_operations fops = {
95    .read = read_f,
96  };
97
98@ has_read_iter @
99identifier fops0.fops;
100identifier read_iter_f;
101@@
102  struct file_operations fops = {
103    .read_iter = read_iter_f,
104  };
105
106@ has_write @
107identifier fops0.fops;
108identifier write_f;
109@@
110  struct file_operations fops = {
111    .write = write_f,
112  };
113
114@ has_write_iter @
115identifier fops0.fops;
116identifier write_iter_f;
117@@
118  struct file_operations fops = {
119    .write_iter = write_iter_f,
120  };
121
122@ has_llseek @
123identifier fops0.fops;
124identifier llseek_f;
125@@
126  struct file_operations fops = {
127    .llseek = llseek_f,
128  };
129
130@ has_no_llseek @
131identifier fops0.fops;
132@@
133  struct file_operations fops = {
134    .llseek = no_llseek,
135  };
136
137@ has_mmap @
138identifier fops0.fops;
139identifier mmap_f;
140@@
141  struct file_operations fops = {
142    .mmap = mmap_f,
143  };
144
145@ has_copy_file_range @
146identifier fops0.fops;
147identifier copy_file_range_f;
148@@
149  struct file_operations fops = {
150    .copy_file_range = copy_file_range_f,
151  };
152
153@ has_remap_file_range @
154identifier fops0.fops;
155identifier remap_file_range_f;
156@@
157  struct file_operations fops = {
158    .remap_file_range = remap_file_range_f,
159  };
160
161@ has_splice_read @
162identifier fops0.fops;
163identifier splice_read_f;
164@@
165  struct file_operations fops = {
166    .splice_read = splice_read_f,
167  };
168
169@ has_splice_write @
170identifier fops0.fops;
171identifier splice_write_f;
172@@
173  struct file_operations fops = {
174    .splice_write = splice_write_f,
175  };
176
177
178// file_operations that is candidate for stream_open conversion - it does not
179// use mmap and other methods that assume @offset access to file.
180//
181// XXX for simplicity require no .{read/write}_iter and no .splice_{read/write} for now.
182// XXX maybe_steam.fops cannot be used in other rules - it gives "bad rule maybe_stream or bad variable fops".
183@ maybe_stream depends on (!has_llseek || has_no_llseek) && !has_mmap && !has_copy_file_range && !has_remap_file_range && !has_read_iter && !has_write_iter && !has_splice_read && !has_splice_write @
184identifier fops0.fops;
185@@
186  struct file_operations fops = {
187  };
188
189
190// ---- conversions ----
191
192// XXX .open = nonseekable_open -> .open = stream_open
193// XXX .open = func -> openfunc -> nonseekable_open
194
195// read & write
196//
197// if both are used in the same file_operations together with an opener -
198// under that conditions we can use stream_open instead of nonseekable_open.
199@ fops_rw depends on maybe_stream @
200identifier fops0.fops, openfunc;
201identifier stream_reader.readstream;
202identifier stream_writer.writestream;
203@@
204  struct file_operations fops = {
205      .open  = openfunc,
206      .read  = readstream,
207      .write = writestream,
208  };
209
210@ report_rw depends on report @
211identifier fops_rw.openfunc;
212position p1;
213@@
214  openfunc(...) {
215    <...
216     nonseekable_open@p1
217    ...>
218  }
219
220@ script:python depends on report && reader_blocks @
221fops << fops0.fops;
222p << report_rw.p1;
223@@
224coccilib.report.print_report(p[0],
225  "ERROR: %s: .read() can deadlock .write(); change nonseekable_open -> stream_open to fix." % (fops,))
226
227@ script:python depends on report && !reader_blocks @
228fops << fops0.fops;
229p << report_rw.p1;
230@@
231coccilib.report.print_report(p[0],
232  "WARNING: %s: .read() and .write() have stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
233
234
235@ explain_rw_deadlocked depends on explain && reader_blocks @
236identifier fops_rw.openfunc;
237@@
238  openfunc(...) {
239    <...
240-    nonseekable_open
241+    nonseekable_open /* read & write (was deadlock) */
242    ...>
243  }
244
245
246@ explain_rw_nodeadlock depends on explain && !reader_blocks @
247identifier fops_rw.openfunc;
248@@
249  openfunc(...) {
250    <...
251-    nonseekable_open
252+    nonseekable_open /* read & write (no direct deadlock) */
253    ...>
254  }
255
256@ patch_rw depends on patch @
257identifier fops_rw.openfunc;
258@@
259  openfunc(...) {
260    <...
261-   nonseekable_open
262+   stream_open
263    ...>
264  }
265
266
267// read, but not write
268@ fops_r depends on maybe_stream && !has_write @
269identifier fops0.fops, openfunc;
270identifier stream_reader.readstream;
271@@
272  struct file_operations fops = {
273      .open  = openfunc,
274      .read  = readstream,
275  };
276
277@ report_r depends on report @
278identifier fops_r.openfunc;
279position p1;
280@@
281  openfunc(...) {
282    <...
283    nonseekable_open@p1
284    ...>
285  }
286
287@ script:python depends on report @
288fops << fops0.fops;
289p << report_r.p1;
290@@
291coccilib.report.print_report(p[0],
292  "WARNING: %s: .read() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
293
294@ explain_r depends on explain @
295identifier fops_r.openfunc;
296@@
297  openfunc(...) {
298    <...
299-   nonseekable_open
300+   nonseekable_open /* read only */
301    ...>
302  }
303
304@ patch_r depends on patch @
305identifier fops_r.openfunc;
306@@
307  openfunc(...) {
308    <...
309-   nonseekable_open
310+   stream_open
311    ...>
312  }
313
314
315// write, but not read
316@ fops_w depends on maybe_stream && !has_read @
317identifier fops0.fops, openfunc;
318identifier stream_writer.writestream;
319@@
320  struct file_operations fops = {
321      .open  = openfunc,
322      .write = writestream,
323  };
324
325@ report_w depends on report @
326identifier fops_w.openfunc;
327position p1;
328@@
329  openfunc(...) {
330    <...
331    nonseekable_open@p1
332    ...>
333  }
334
335@ script:python depends on report @
336fops << fops0.fops;
337p << report_w.p1;
338@@
339coccilib.report.print_report(p[0],
340  "WARNING: %s: .write() has stream semantic; safe to change nonseekable_open -> stream_open." % (fops,))
341
342@ explain_w depends on explain @
343identifier fops_w.openfunc;
344@@
345  openfunc(...) {
346    <...
347-   nonseekable_open
348+   nonseekable_open /* write only */
349    ...>
350  }
351
352@ patch_w depends on patch @
353identifier fops_w.openfunc;
354@@
355  openfunc(...) {
356    <...
357-   nonseekable_open
358+   stream_open
359    ...>
360  }
361
362
363// no read, no write - don't change anything
364