@@ -52,6 +52,25 @@ static void __init find_tempdir(void)
5252 strcat (tempdir , "/" );
5353}
5454
55+ /*
56+ * Remove bytes from the front of the buffer and refill it so that if there's a
57+ * partial string that we care about, it will be completed, and we can recognize
58+ * it.
59+ */
60+ static int pop (int fd , char * buf , size_t size , size_t npop )
61+ {
62+ ssize_t n ;
63+ size_t len = strlen (& buf [npop ]);
64+
65+ memmove (buf , & buf [npop ], len + 1 );
66+ n = read (fd , & buf [len ], size - len - 1 );
67+ if (n < 0 )
68+ return - errno ;
69+
70+ buf [len + n ] = '\0' ;
71+ return 1 ;
72+ }
73+
5574/*
5675 * This will return 1, with the first character in buf being the
5776 * character following the next instance of c in the file. This will
@@ -61,7 +80,6 @@ static void __init find_tempdir(void)
6180static int next (int fd , char * buf , size_t size , char c )
6281{
6382 ssize_t n ;
64- size_t len ;
6583 char * ptr ;
6684
6785 while ((ptr = strchr (buf , c )) == NULL ) {
@@ -74,20 +92,129 @@ static int next(int fd, char *buf, size_t size, char c)
7492 buf [n ] = '\0' ;
7593 }
7694
77- ptr ++ ;
78- len = strlen (ptr );
79- memmove (buf , ptr , len + 1 );
95+ return pop (fd , buf , size , ptr - buf + 1 );
96+ }
97+
98+ /*
99+ * Decode an octal-escaped and space-terminated path of the form used by
100+ * /proc/mounts. May be used to decode a path in-place. "out" must be at least
101+ * as large as the input. The output is always null-terminated. "len" gets the
102+ * length of the output, excluding the trailing null. Returns 0 if a full path
103+ * was successfully decoded, otherwise an error.
104+ */
105+ static int decode_path (const char * in , char * out , size_t * len )
106+ {
107+ char * first = out ;
108+ int c ;
109+ int i ;
110+ int ret = - EINVAL ;
111+ while (1 ) {
112+ switch (* in ) {
113+ case '\0' :
114+ goto out ;
115+
116+ case ' ' :
117+ ret = 0 ;
118+ goto out ;
119+
120+ case '\\' :
121+ in ++ ;
122+ c = 0 ;
123+ for (i = 0 ; i < 3 ; i ++ ) {
124+ if (* in < '0' || * in > '7' )
125+ goto out ;
126+ c = (c << 3 ) | (* in ++ - '0' );
127+ }
128+ * (unsigned char * )out ++ = (unsigned char ) c ;
129+ break ;
130+
131+ default :
132+ * out ++ = * in ++ ;
133+ break ;
134+ }
135+ }
136+
137+ out :
138+ * out = '\0' ;
139+ * len = out - first ;
140+ return ret ;
141+ }
142+
143+ /*
144+ * Computes the length of s when encoded with three-digit octal escape sequences
145+ * for the characters in chars.
146+ */
147+ static size_t octal_encoded_length (const char * s , const char * chars )
148+ {
149+ size_t len = strlen (s );
150+ while ((s = strpbrk (s , chars )) != NULL ) {
151+ len += 3 ;
152+ s ++ ;
153+ }
154+
155+ return len ;
156+ }
157+
158+ enum {
159+ OUTCOME_NOTHING_MOUNTED ,
160+ OUTCOME_TMPFS_MOUNT ,
161+ OUTCOME_NON_TMPFS_MOUNT ,
162+ };
163+
164+ /* Read a line of /proc/mounts data looking for a tmpfs mount at "path". */
165+ static int read_mount (int fd , char * buf , size_t bufsize , const char * path ,
166+ int * outcome )
167+ {
168+ int found ;
169+ int match ;
170+ char * space ;
171+ size_t len ;
172+
173+ enum {
174+ MATCH_NONE ,
175+ MATCH_EXACT ,
176+ MATCH_PARENT ,
177+ };
178+
179+ found = next (fd , buf , bufsize , ' ' );
180+ if (found != 1 )
181+ return found ;
80182
81183 /*
82- * Refill the buffer so that if there's a partial string that we care
83- * about, it will be completed, and we can recognize it .
184+ * If there's no following space in the buffer, then this path is
185+ * truncated, so it can't be the one we're looking for .
84186 */
85- n = read (fd , & buf [len ], size - len - 1 );
86- if (n < 0 )
87- return - errno ;
187+ space = strchr (buf , ' ' );
188+ if (space ) {
189+ match = MATCH_NONE ;
190+ if (!decode_path (buf , buf , & len )) {
191+ if (!strcmp (buf , path ))
192+ match = MATCH_EXACT ;
193+ else if (!strncmp (buf , path , len )
194+ && (path [len ] == '/' || !strcmp (buf , "/" )))
195+ match = MATCH_PARENT ;
196+ }
197+
198+ found = pop (fd , buf , bufsize , space - buf + 1 );
199+ if (found != 1 )
200+ return found ;
201+
202+ switch (match ) {
203+ case MATCH_EXACT :
204+ if (!strncmp (buf , "tmpfs" , strlen ("tmpfs" )))
205+ * outcome = OUTCOME_TMPFS_MOUNT ;
206+ else
207+ * outcome = OUTCOME_NON_TMPFS_MOUNT ;
208+ break ;
88209
89- buf [len + n ] = '\0' ;
90- return 1 ;
210+ case MATCH_PARENT :
211+ /* This mount obscures any previous ones. */
212+ * outcome = OUTCOME_NOTHING_MOUNTED ;
213+ break ;
214+ }
215+ }
216+
217+ return next (fd , buf , bufsize , '\n' );
91218}
92219
93220/* which_tmpdir is called only during early boot */
@@ -106,8 +233,12 @@ static int checked_tmpdir = 0;
106233 */
107234static void which_tmpdir (void )
108235{
109- int fd , found ;
110- char buf [128 ] = { '\0' };
236+ int fd ;
237+ int found ;
238+ int outcome ;
239+ char * path ;
240+ char * buf ;
241+ size_t bufsize ;
111242
112243 if (checked_tmpdir )
113244 return ;
@@ -116,49 +247,66 @@ static void which_tmpdir(void)
116247
117248 printf ("Checking for tmpfs mount on /dev/shm..." );
118249
250+ path = realpath ("/dev/shm" , NULL );
251+ if (!path ) {
252+ printf ("failed to check real path, errno = %d\n" , errno );
253+ return ;
254+ }
255+ printf ("%s..." , path );
256+
257+ /*
258+ * The buffer needs to be able to fit the full octal-escaped path, a
259+ * space, and a trailing null in order to successfully decode it.
260+ */
261+ bufsize = octal_encoded_length (path , " \t\n\\" ) + 2 ;
262+
263+ if (bufsize < 128 )
264+ bufsize = 128 ;
265+
266+ buf = malloc (bufsize );
267+ if (!buf ) {
268+ printf ("malloc failed, errno = %d\n" , errno );
269+ goto out ;
270+ }
271+ buf [0 ] = '\0' ;
272+
119273 fd = open ("/proc/mounts" , O_RDONLY );
120274 if (fd < 0 ) {
121275 printf ("failed to open /proc/mounts, errno = %d\n" , errno );
122- return ;
276+ goto out1 ;
123277 }
124278
279+ outcome = OUTCOME_NOTHING_MOUNTED ;
125280 while (1 ) {
126- found = next (fd , buf , ARRAY_SIZE (buf ), ' ' );
127- if (found != 1 )
128- break ;
129-
130- if (!strncmp (buf , "/dev/shm" , strlen ("/dev/shm" )))
131- goto found ;
132-
133- found = next (fd , buf , ARRAY_SIZE (buf ), '\n' );
281+ found = read_mount (fd , buf , bufsize , path , & outcome );
134282 if (found != 1 )
135283 break ;
136284 }
137285
138- err :
139- if (found == 0 )
140- printf ("nothing mounted on /dev/shm\n" );
141- else if (found < 0 )
286+ if (found < 0 ) {
142287 printf ("read returned errno %d\n" , - found );
288+ } else {
289+ switch (outcome ) {
290+ case OUTCOME_TMPFS_MOUNT :
291+ printf ("OK\n" );
292+ default_tmpdir = "/dev/shm" ;
293+ break ;
143294
144- out :
145- close (fd );
146-
147- return ;
148-
149- found :
150- found = next (fd , buf , ARRAY_SIZE (buf ), ' ' );
151- if (found != 1 )
152- goto err ;
295+ case OUTCOME_NON_TMPFS_MOUNT :
296+ printf ("not tmpfs\n" );
297+ break ;
153298
154- if (strncmp (buf , "tmpfs" , strlen ("tmpfs" ))) {
155- printf ("not tmpfs\n" );
156- goto out ;
299+ default :
300+ printf ("nothing mounted on /dev/shm\n" );
301+ break ;
302+ }
157303 }
158304
159- printf ("OK\n" );
160- default_tmpdir = "/dev/shm" ;
161- goto out ;
305+ close (fd );
306+ out1 :
307+ free (buf );
308+ out :
309+ free (path );
162310}
163311
164312static int __init make_tempfile (const char * template , char * * out_tempname ,
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