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authorLennart Poettering <lennart@poettering.net>2016-04-20 19:27:32 +0200
committerLennart Poettering <lennart@poettering.net>2016-04-22 16:16:53 +0200
commit03532f0ae0fae40f9f04091340e2bf156d0ec21a (patch)
tree52c0ad443ed1cbec01971d9284ca47ac276f00e9 /src/basic/fileio.c
parentf8591ee1b6c152055feed7a872159e67859fd83d (diff)
coredump,basic: generalize O_TMPFILE handling a bit
This moves the O_TMPFILE handling from the coredumping code into common library code, and generalizes it as open_tmpfile_linkable() + link_tmpfile(). The existing open_tmpfile() function (which creates an unlinked temporary file that cannot be linked into the fs) is renamed to open_tmpfile_unlinkable(), to make the distinction clear. Thus, code may now choose between: a) open_tmpfile_linkable() + link_tmpfile() b) open_tmpfile_unlinkable() Depending on whether they want a file that may be linked back into the fs later on or not. In a later commit we should probably convert fopen_temporary() to make use of open_tmpfile_linkable(). Followup for: #3065
Diffstat (limited to 'src/basic/fileio.c')
-rw-r--r--src/basic/fileio.c124
1 files changed, 100 insertions, 24 deletions
diff --git a/src/basic/fileio.c b/src/basic/fileio.c
index 69590941e5..2a9b6e46ad 100644
--- a/src/basic/fileio.c
+++ b/src/basic/fileio.c
@@ -1083,30 +1083,6 @@ int mkostemp_safe(char *pattern, int flags) {
return fd;
}
-int open_tmpfile(const char *path, int flags) {
- char *p;
- int fd;
-
- assert(path);
-
-#ifdef O_TMPFILE
- /* Try O_TMPFILE first, if it is supported */
- fd = open(path, flags|O_TMPFILE|O_EXCL, S_IRUSR|S_IWUSR);
- if (fd >= 0)
- return fd;
-#endif
-
- /* Fall back to unguessable name + unlinking */
- p = strjoina(path, "/systemd-tmp-XXXXXX");
-
- fd = mkostemp_safe(p, flags);
- if (fd < 0)
- return fd;
-
- unlink(p);
- return fd;
-}
-
int tempfn_xxxxxx(const char *p, const char *extra, char **ret) {
const char *fn;
char *t;
@@ -1278,3 +1254,103 @@ int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space)
return fputs(s, f);
}
+
+int open_tmpfile_unlinkable(const char *directory, int flags) {
+ char *p;
+ int fd;
+
+ assert(directory);
+
+ /* Returns an unlinked temporary file that cannot be linked into the file system anymore */
+
+#ifdef O_TMPFILE
+ /* Try O_TMPFILE first, if it is supported */
+ fd = open(directory, flags|O_TMPFILE|O_EXCL, S_IRUSR|S_IWUSR);
+ if (fd >= 0)
+ return fd;
+#endif
+
+ /* Fall back to unguessable name + unlinking */
+ p = strjoina(directory, "/systemd-tmp-XXXXXX");
+
+ fd = mkostemp_safe(p, flags);
+ if (fd < 0)
+ return fd;
+
+ (void) unlink(p);
+
+ return fd;
+}
+
+int open_tmpfile_linkable(const char *target, int flags, char **ret_path) {
+ _cleanup_free_ char *tmp = NULL;
+ int r, fd;
+
+ assert(target);
+ assert(ret_path);
+
+ /* Don't allow O_EXCL, as that has a special meaning for O_TMPFILE */
+ assert((flags & O_EXCL) == 0);
+
+ /* Creates a temporary file, that shall be renamed to "target" later. If possible, this uses O_TMPFILE – in
+ * which case "ret_path" will be returned as NULL. If not possible a the tempoary path name used is returned in
+ * "ret_path". Use link_tmpfile() below to rename the result after writing the file in full. */
+
+#ifdef O_TMPFILE
+ {
+ _cleanup_free_ char *dn = NULL;
+
+ dn = dirname_malloc(target);
+ if (!dn)
+ return -ENOMEM;
+
+ fd = open(dn, O_TMPFILE|flags, 0640);
+ if (fd >= 0) {
+ *ret_path = NULL;
+ return fd;
+ }
+
+ log_debug_errno(errno, "Failed to use O_TMPFILE on %s: %m", dn);
+ }
+#endif
+
+ r = tempfn_random(target, NULL, &tmp);
+ if (r < 0)
+ return r;
+
+ fd = open(tmp, O_CREAT|O_EXCL|O_NOFOLLOW|O_NOCTTY|flags, 0640);
+ if (fd < 0)
+ return -errno;
+
+ *ret_path = tmp;
+ tmp = NULL;
+
+ return fd;
+}
+
+int link_tmpfile(int fd, const char *path, const char *target) {
+
+ assert(fd >= 0);
+ assert(target);
+
+ /* Moves a temporary file created with open_tmpfile() above into its final place. if "path" is NULL an fd
+ * created with O_TMPFILE is assumed, and linkat() is used. Otherwise it is assumed O_TMPFILE is not supported
+ * on the directory, and renameat2() is used instead.
+ *
+ * Note that in both cases we will not replace existing files. This is because linkat() dos not support this
+ * operation currently (renameat2() does), and there is no nice way to emulate this. */
+
+ if (path) {
+ if (rename_noreplace(AT_FDCWD, path, AT_FDCWD, target) < 0)
+ return -errno;
+ } else {
+ char proc_fd_path[strlen("/proc/self/fd/") + DECIMAL_STR_MAX(fd) + 1];
+
+ xsprintf(proc_fd_path, "/proc/self/fd/%i", fd);
+
+ if (linkat(AT_FDCWD, proc_fd_path, AT_FDCWD, target, AT_SYMLINK_FOLLOW) < 0)
+ return -errno;
+ }
+
+ return 0;
+}