Bug Summary

File:src/usr.bin/lex/filter.c
Warning:line 56, column 17
Access to field 'filter_func' results in a dereference of a null pointer (loaded from variable 'f')

Annotated Source Code

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clang -cc1 -cc1 -triple amd64-unknown-openbsd7.0 -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name filter.c -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -setup-static-analyzer -mrelocation-model pic -pic-level 1 -pic-is-pie -mframe-pointer=all -relaxed-aliasing -fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu x86-64 -target-feature +retpoline-indirect-calls -target-feature +retpoline-indirect-branches -tune-cpu generic -debugger-tuning=gdb -fcoverage-compilation-dir=/usr/src/usr.bin/lex/obj -resource-dir /usr/local/lib/clang/13.0.0 -I . -I /usr/src/usr.bin/lex -D HAVE_CONFIG_H -internal-isystem /usr/local/lib/clang/13.0.0/include -internal-externc-isystem /usr/include -O2 -fdebug-compilation-dir=/usr/src/usr.bin/lex/obj -ferror-limit 19 -fwrapv -D_RET_PROTECTOR -ret-protector -fgnuc-version=4.2.1 -vectorize-loops -vectorize-slp -fno-builtin-malloc -fno-builtin-calloc -fno-builtin-realloc -fno-builtin-valloc -fno-builtin-free -fno-builtin-strdup -fno-builtin-strndup -analyzer-output=html -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /home/ben/Projects/vmm/scan-build/2022-01-12-194120-40624-1 -x c /usr/src/usr.bin/lex/filter.c
1/* $OpenBSD: filter.c,v 1.9 2017/08/30 02:54:07 lteo Exp $ */
2
3/* filter - postprocessing of flex output through filters */
4
5/* This file is part of flex. */
6
7/* Redistribution and use in source and binary forms, with or without */
8/* modification, are permitted provided that the following conditions */
9/* are met: */
10
11/* 1. Redistributions of source code must retain the above copyright */
12/* notice, this list of conditions and the following disclaimer. */
13/* 2. Redistributions in binary form must reproduce the above copyright */
14/* notice, this list of conditions and the following disclaimer in the */
15/* documentation and/or other materials provided with the distribution. */
16
17/* Neither the name of the University nor the names of its contributors */
18/* may be used to endorse or promote products derived from this software */
19/* without specific prior written permission. */
20
21/* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR */
22/* IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED */
23/* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR */
24/* PURPOSE. */
25
26#include "flexdef.h"
27static const char *check_4_gnu_m4 =
28"m4_dnl ifdef(`__gnu__', ,"
29"`errprint(Flex requires GNU M4. Set the PATH or set the M4 environment variable to its path name.)"
30" m4exit(2)')\n";
31
32
33/** global chain. */
34struct filter *output_chain = NULL((void *)0);
35
36/* Allocate and initialize an external filter.
37 * @param chain the current chain or NULL for new chain
38 * @param cmd the command to execute.
39 * @param ... a NULL terminated list of (const char*) arguments to command,
40 * not including argv[0].
41 * @return newest filter in chain
42 */
43struct filter *
44filter_create_ext(struct filter * chain, const char *cmd,
45 ...)
46{
47 struct filter *f;
48 int max_args;
49 const char *s;
50 va_list ap;
51
52 /* allocate and initialize new filter */
53 f = calloc(sizeof(struct filter), 1);
1
Value assigned to 'f'
→
54 if (!f)
2
←
Assuming 'f' is null
→
3
←
Taking true branch
→
55 flexerror(_("calloc failed (f) in filter_create_ext")"calloc failed (f) in filter_create_ext");
56 f->filter_func = NULL((void *)0);
4
←
Access to field 'filter_func' results in a dereference of a null pointer (loaded from variable 'f')
57 f->extra = NULL((void *)0);
58 f->next = NULL((void *)0);
59 f->argc = 0;
60
61 if (chain != NULL((void *)0)) {
62 /* append f to end of chain */
63 while (chain->next)
64 chain = chain->next;
65 chain->next = f;
66 }
67 /* allocate argv, and populate it with the argument list. */
68 max_args = 8;
69 f->argv = malloc(sizeof(char *) * (max_args + 1));
70 if (!f->argv)
71 flexerror(_("malloc failed (f->argv) in filter_create_ext")"malloc failed (f->argv) in filter_create_ext");
72 f->argv[f->argc++] = cmd;
73
74 va_start(ap, cmd)__builtin_va_start(ap, cmd);
75 while ((s = va_arg(ap, const char *)__builtin_va_arg(ap, const char *)) != NULL((void *)0)) {
76 if (f->argc >= max_args) {
77 max_args += 8;
78 f->argv = realloc(f->argv,
79 sizeof(char *) * (max_args + 1));
80 }
81 f->argv[f->argc++] = s;
82 }
83 f->argv[f->argc] = NULL((void *)0);
84
85 va_end(ap)__builtin_va_end(ap);
86 return f;
87}
88
89/* Allocate and initialize an internal filter.
90 * @param chain the current chain or NULL for new chain
91 * @param filter_func The function that will perform the filtering.
92 * filter_func should return 0 if successful, and -1
93 * if an error occurs -- or it can simply exit().
94 * @param extra optional user-defined data to pass to the filter.
95 * @return newest filter in chain
96 */
97struct filter *
98filter_create_int(struct filter * chain,
99 int (*filter_func) (struct filter *),
100 void *extra)
101{
102 struct filter *f;
103
104 /* allocate and initialize new filter */
105 f = calloc(sizeof(struct filter), 1);
106 if (!f)
107 flexerror(_("calloc failed in filter_create_int")"calloc failed in filter_create_int");
108 f->next = NULL((void *)0);
109 f->argc = 0;
110 f->argv = NULL((void *)0);
111
112 f->filter_func = filter_func;
113 f->extra = extra;
114
115 if (chain != NULL((void *)0)) {
116 /* append f to end of chain */
117 while (chain->next)
118 chain = chain->next;
119 chain->next = f;
120 }
121 return f;
122}
123
124/** Fork and exec entire filter chain.
125 * @param chain The head of the chain.
126 * @return true on success.
127 */
128bool_Bool
129filter_apply_chain(struct filter * chain)
130{
131 int pid, pipes[2];
132
133 /*
134 * Tricky recursion, since we want to begin the chain at the END.
135 * Why? Because we need all the forked processes to be children of
136 * the main flex process.
137 */
138 if (chain)
139 filter_apply_chain(chain->next);
140 else
141 return true1;
142
143 /*
144 * Now we are the right-most unprocessed link in the chain.
145 */
146
147 fflush(stdout(&__sF[1]));
148 fflush(stderr(&__sF[2]));
149
150
151 if (pipe(pipes) == -1)
152 flexerror(_("pipe failed")"pipe failed");
153
154 if ((pid = fork()) == -1)
155 flexerror(_("fork failed")"fork failed");
156
157 if (pid == 0) {
158 /* child */
159
160 /*
161 * We need stdin (the FILE* stdin) to connect to this new
162 * pipe. There is no portable way to set stdin to a new file
163 * descriptor, as stdin is not an lvalue on some systems
164 * (BSD). So we dup the new pipe onto the stdin descriptor
165 * and use a no-op fseek to sync the stream. This is a Hail
166 * Mary situation. It seems to work.
167 */
168 close(pipes[1]);
169 clearerr(stdin)(!__isthreaded ? ((void)(((&__sF[0]))->_flags &= ~
(0x0040|0x0020))) : (clearerr)((&__sF[0])));
170 if (dup2(pipes[0], fileno(stdin)(!__isthreaded ? (((&__sF[0]))->_file) : (fileno)((&
__sF[0])))) == -1)
171 flexfatal(_("dup2(pipes[0],0)")"dup2(pipes[0],0)");
172 close(pipes[0]);
173 fseek(stdin(&__sF[0]), 0, SEEK_CUR1);
174
175 /* run as a filter, either internally or by exec */
176 if (chain->filter_func) {
177 if (chain->filter_func(chain) == -1)
178 flexfatal(_("filter_func failed")"filter_func failed");
179 exit(0);
180 } else {
181 execvp(chain->argv[0],
182 (char **const) (chain->argv));
183 lerrsf_fatal(_("exec of %s failed")"exec of %s failed",
184 chain->argv[0]);
185 }
186
187 exit(1);
188 }
189 /* Parent */
190 close(pipes[0]);
191 if (dup2(pipes[1], fileno(stdout)(!__isthreaded ? (((&__sF[1]))->_file) : (fileno)((&
__sF[1])))) == -1)
192 flexfatal(_("dup2(pipes[1],1)")"dup2(pipes[1],1)");
193 close(pipes[1]);
194 fseek(stdout(&__sF[1]), 0, SEEK_CUR1);
195
196 return true1;
197}
198
199/** Truncate the chain to max_len number of filters.
200 * @param chain the current chain.
201 * @param max_len the maximum length of the chain.
202 * @return the resulting length of the chain.
203 */
204int
205filter_truncate(struct filter * chain, int max_len)
206{
207 int len = 1;
208
209 if (!chain)
210 return 0;
211
212 while (chain->next && len < max_len) {
213 chain = chain->next;
214 ++len;
215 }
216
217 chain->next = NULL((void *)0);
218 return len;
219}
220
221/** Splits the chain in order to write to a header file.
222 * Similar in spirit to the 'tee' program.
223 * The header file name is in extra.
224 * @return 0 (zero) on success, and -1 on failure.
225 */
226int
227filter_tee_header(struct filter * chain)
228{
229 /*
230 * This function reads from stdin and writes to both the C file and
231 * the header file at the same time.
232 */
233
234 const int readsz = 512;
235 char *buf;
236 int to_cfd = -1;
237 FILE *to_c = NULL((void *)0), *to_h = NULL((void *)0);
238 bool_Bool write_header;
239
240 write_header = (chain->extra != NULL((void *)0));
241
242 /*
243 * Store a copy of the stdout pipe, which is already piped to C file
244 * through the running chain. Then create a new pipe to the H file as
245 * stdout, and fork the rest of the chain again.
246 */
247
248 if ((to_cfd = dup(1)) == -1)
249 flexfatal(_("dup(1) failed")"dup(1) failed");
250 to_c = fdopen(to_cfd, "w");
251
252 if (write_header) {
253 if (freopen((char *) chain->extra, "w", stdout(&__sF[1])) == NULL((void *)0))
254 flexfatal(_("freopen(headerfilename) failed")"freopen(headerfilename) failed");
255
256 filter_apply_chain(chain->next);
257 to_h = stdout(&__sF[1]);
258 }
259 /*
260 * Now to_c is a pipe to the C branch, and to_h is a pipe to the H
261 * branch.
262 */
263
264 if (write_header) {
265 fputs(check_4_gnu_m4, to_h);
266 fputs("m4_changecom`'m4_dnl\n", to_h);
267 fputs("m4_changequote`'m4_dnl\n", to_h);
268 fputs("m4_changequote([[,]])[[]]m4_dnl\n", to_h);
269 fputs("m4_define([[M4_YY_NOOP]])[[]]m4_dnl\n", to_h);
270 fputs("m4_define( [[M4_YY_IN_HEADER]],[[]])m4_dnl\n",
271 to_h);
272 fprintf(to_h, "#ifndef %sHEADER_H\n", prefix);
273 fprintf(to_h, "#define %sHEADER_H 1\n", prefix);
274 fprintf(to_h, "#define %sIN_HEADER 1\n\n", prefix);
275 fprintf(to_h,
276 "m4_define( [[M4_YY_OUTFILE_NAME]],[[%s]])m4_dnl\n",
277 headerfilename ? headerfilename : "<stdout>");
278
279 }
280 fputs(check_4_gnu_m4, to_c);
281 fputs("m4_changecom`'m4_dnl\n", to_c);
282 fputs("m4_changequote`'m4_dnl\n", to_c);
283 fputs("m4_changequote([[,]])[[]]m4_dnl\n", to_c);
284 fputs("m4_define([[M4_YY_NOOP]])[[]]m4_dnl\n", to_c);
285 fprintf(to_c, "m4_define( [[M4_YY_OUTFILE_NAME]],[[%s]])m4_dnl\n",
286 outfilename ? outfilename : "<stdout>");
287
288 buf = malloc(readsz);
289 if (!buf)
290 flexerror(_("malloc failed in filter_tee_header")"malloc failed in filter_tee_header");
291 while (fgets(buf, readsz, stdin(&__sF[0]))) {
292 fputs(buf, to_c);
293 if (write_header)
294 fputs(buf, to_h);
295 }
296
297 if (write_header) {
298 fprintf(to_h, "\n");
299
300 /*
301 * write a fake line number. It will get fixed by the linedir
302 * filter.
303 */
304 fprintf(to_h, "#line 4000 \"M4_YY_OUTFILE_NAME\"\n");
305
306 fprintf(to_h, "#undef %sIN_HEADER\n", prefix);
307 fprintf(to_h, "#endif /* %sHEADER_H */\n", prefix);
308 fputs("m4_undefine( [[M4_YY_IN_HEADER]])m4_dnl\n", to_h);
309
310 fflush(to_h);
311 if (ferror(to_h)(!__isthreaded ? (((to_h)->_flags & 0x0040) != 0) : (ferror
)(to_h)))
312 lerrsf(_("error writing output file %s")"error writing output file %s",
313 (char *) chain->extra);
314
315 else if (fclose(to_h))
316 lerrsf(_("error closing output file %s")"error closing output file %s",
317 (char *) chain->extra);
318 }
319 fflush(to_c);
320 if (ferror(to_c)(!__isthreaded ? (((to_c)->_flags & 0x0040) != 0) : (ferror
)(to_c)))
321 lerrsf(_("error writing output file %s")"error writing output file %s",
322 outfilename ? outfilename : "<stdout>");
323
324 else if (fclose(to_c))
325 lerrsf(_("error closing output file %s")"error closing output file %s",
326 outfilename ? outfilename : "<stdout>");
327
328 while (wait(0) > 0);
329
330 exit(0);
331 return 0;
332}
333
334/** Adjust the line numbers in the #line directives of the generated scanner.
335 * After the m4 expansion, the line numbers are incorrect since the m4 macros
336 * can add or remove lines. This only adjusts line numbers for generated code,
337 * not user code. This also happens to be a good place to squeeze multiple
338 * blank lines into a single blank line.
339 */
340int
341filter_fix_linedirs(struct filter * chain)
342{
343 char *buf;
344 const int readsz = 512;
345 int lineno = 1;
346 bool_Bool in_gen = true1; /* in generated code */
347 bool_Bool last_was_blank = false0;
348
349 if (!chain)
350 return 0;
351
352 buf = malloc(readsz);
353 if (!buf)
354 flexerror(_("malloc failed in filter_fix_linedirs")"malloc failed in filter_fix_linedirs");
355
356 while (fgets(buf, readsz, stdin(&__sF[0]))) {
357
358 regmatch_t m[10];
359
360 /* Check for #line directive. */
361 if (buf[0] == '#'
362 && regexec(&regex_linedir, buf, 3, m, 0) == 0) {
363
364 int num;
365 char *fname;
366
367 /* extract the line number and filename */
368 num = regmatch_strtol(&m[1], buf, NULL((void *)0), 0);
369 fname = regmatch_dup(&m[2], buf);
370
371 if (strcmp(fname,
372 outfilename ? outfilename : "<stdout>") == 0 ||
373 strcmp(fname, headerfilename ? headerfilename :
374 "<stdout>") == 0) {
375
376 char *s1, *s2;
377 char filename[MAXLINE2048];
378
379 s1 = fname;
380 s2 = filename;
381
382 while ((s2 - filename) < (MAXLINE2048 - 1) && *s1) {
383 /* Escape the backslash */
384 if (*s1 == '\\')
385 *s2++ = '\\';
386 /* Escape the double quote */
387 if (*s1 == '\"')
388 *s2++ = '\\';
389 /* Copy the character as usual */
390 *s2++ = *s1++;
391 }
392
393 *s2 = '\0';
394
395 /* Adjust the line directives. */
396 in_gen = true1;
397 snprintf(buf, readsz, "#line %d \"%s\"\n",
398 lineno + 1, filename);
399 } else {
400 /*
401 * it's a #line directive for code we didn't
402 * write
403 */
404 in_gen = false0;
405 }
406
407 free(fname);
408 last_was_blank = false0;
409 }
410 /* squeeze blank lines from generated code */
411 else if (in_gen &&
412 regexec(&regex_blank_line, buf, 0, NULL((void *)0), 0) == 0) {
413 if (last_was_blank)
414 continue;
415 else
416 last_was_blank = true1;
417 } else {
418 /* it's a line of normal, non-empty code. */
419 last_was_blank = false0;
420 }
421
422 fputs(buf, stdout(&__sF[1]));
423 lineno++;
424 }
425 fflush(stdout(&__sF[1]));
426 if (ferror(stdout)(!__isthreaded ? ((((&__sF[1]))->_flags & 0x0040) !=
0) : (ferror)((&__sF[1]))))
427 lerrsf(_("error writing output file %s")"error writing output file %s",
428 outfilename ? outfilename : "<stdout>");
429
430 else if (fclose(stdout(&__sF[1])))
431 lerrsf(_("error closing output file %s")"error closing output file %s",
432 outfilename ? outfilename : "<stdout>");
433
434 return 0;
435}