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authorZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2014-01-25 23:35:28 -0500
committerZbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl>2014-01-27 23:17:02 -0500
commit65b3903ff576488eaabb51d3c4fbf9c73d867d7c (patch)
tree0343e9d79057f6ca67acb87d6cc06f45ab7a1384 /src/shared
parent8e33886ec582336564ae11b80023abe93d7599c0 (diff)
journal: guarantee async-signal-safety in sd_journald_sendv
signal(7) provides a list of functions which may be called from a signal handler. Other functions, which only call those functions and don't access global memory and are reentrant are also safe. sd_j_sendv was mostly OK, but would call mkostemp and writev in a fallback path, which are unsafe. Being able to call sd_j_sendv in a async-signal-safe way is important because it allows it be used in signal handlers. Safety is achieved by replacing mkostemp with open(O_TMPFILE) and an open-coded writev replacement which uses write. Unfortunately, O_TMPFILE is only available on kernels >= 3.11. When O_TMPFILE is unavailable, an open-coded mkostemp is used. https://bugzilla.gnome.org/show_bug.cgi?id=722889
Diffstat (limited to 'src/shared')
-rw-r--r--src/shared/def.h1
-rw-r--r--src/shared/missing.h16
-rw-r--r--src/shared/util.c54
-rw-r--r--src/shared/util.h3
4 files changed, 63 insertions, 11 deletions
diff --git a/src/shared/def.h b/src/shared/def.h
index a2304fddda..7777756aad 100644
--- a/src/shared/def.h
+++ b/src/shared/def.h
@@ -44,6 +44,7 @@
#define LOWERCASE_LETTERS "abcdefghijklmnopqrstuvwxyz"
#define UPPERCASE_LETTERS "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
#define LETTERS LOWERCASE_LETTERS UPPERCASE_LETTERS
+#define ALPHANUMERICAL LETTERS DIGITS
#define REBOOT_PARAM_FILE "/run/systemd/reboot-param"
diff --git a/src/shared/missing.h b/src/shared/missing.h
index 6c038d9f08..4e62100030 100644
--- a/src/shared/missing.h
+++ b/src/shared/missing.h
@@ -301,25 +301,29 @@ static inline int name_to_handle_at(int fd, const char *name, struct file_handle
#endif
#ifndef CIFS_MAGIC_NUMBER
-#define CIFS_MAGIC_NUMBER 0xFF534D42
+# define CIFS_MAGIC_NUMBER 0xFF534D42
#endif
#ifndef TFD_TIMER_CANCEL_ON_SET
-#define TFD_TIMER_CANCEL_ON_SET (1 << 1)
+# define TFD_TIMER_CANCEL_ON_SET (1 << 1)
#endif
#ifndef SO_REUSEPORT
-#define SO_REUSEPORT 15
+# define SO_REUSEPORT 15
#endif
#ifndef EVIOCREVOKE
-#define EVIOCREVOKE _IOW('E', 0x91, int)
+# define EVIOCREVOKE _IOW('E', 0x91, int)
#endif
#ifndef DRM_IOCTL_SET_MASTER
-#define DRM_IOCTL_SET_MASTER _IO('d', 0x1e)
+# define DRM_IOCTL_SET_MASTER _IO('d', 0x1e)
#endif
#ifndef DRM_IOCTL_DROP_MASTER
-#define DRM_IOCTL_DROP_MASTER _IO('d', 0x1f)
+# define DRM_IOCTL_DROP_MASTER _IO('d', 0x1f)
+#endif
+
+#ifndef TMP_MAX
+# define TMP_MAX 238328
#endif
diff --git a/src/shared/util.c b/src/shared/util.c
index 27fc9594cd..a437d9b127 100644
--- a/src/shared/util.c
+++ b/src/shared/util.c
@@ -6109,6 +6109,53 @@ int getpeersec(int fd, char **ret) {
return 0;
}
+int writev_safe(int fd, const struct iovec *w, int j) {
+ for (int i = 0; i < j; i++) {
+ size_t written = 0;
+
+ while (written < w[i].iov_len) {
+ ssize_t r;
+
+ r = write(fd, (char*) w[i].iov_base + written, w[i].iov_len - written);
+ if (r < 0 && errno != -EINTR)
+ return -errno;
+
+ written += r;
+ }
+ }
+
+ return 0;
+}
+
+int mkostemp_safe(char *pattern, int flags) {
+ char *s = pattern + strlen(pattern) - 6;
+ uint64_t tries = TMP_MAX;
+ int randfd, fd, i;
+
+ assert(streq(s, "XXXXXX"));
+
+ randfd = open("/dev/urandom", O_RDONLY);
+ if (randfd < 0)
+ return -ENOSYS;
+
+ while (tries--) {
+ fd = read(randfd, s, 6);
+ if (fd == 0)
+ return -ENOSYS;
+
+ for (i = 0; i < 6; i++)
+ s[i] = ALPHANUMERICAL[(unsigned) s[i] % strlen(ALPHANUMERICAL)];
+
+ fd = open(pattern, flags|O_EXCL|O_CREAT, S_IRUSR|S_IWUSR);
+ if (fd >= 0)
+ return fd;
+ if (!IN_SET(errno, EEXIST, EINTR))
+ return -errno;
+ }
+
+ return -EEXIST;
+}
+
int open_tmpfile(const char *path, int flags) {
int fd;
char *p;
@@ -6120,12 +6167,9 @@ int open_tmpfile(const char *path, int flags) {
#endif
p = strappenda(path, "/systemd-tmp-XXXXXX");
- RUN_WITH_UMASK(0077) {
- fd = mkostemp(p, O_RDWR|O_CLOEXEC);
- }
-
+ fd = mkostemp_safe(p, O_RDWR|O_CLOEXEC);
if (fd < 0)
- return -errno;
+ return fd;
unlink(p);
return fd;
diff --git a/src/shared/util.h b/src/shared/util.h
index 630137a53a..1169864c3a 100644
--- a/src/shared/util.h
+++ b/src/shared/util.h
@@ -850,4 +850,7 @@ bool pid_valid(pid_t pid);
int getpeercred(int fd, struct ucred *ucred);
int getpeersec(int fd, char **ret);
+int writev_safe(int fd, const struct iovec *w, int j);
+
+int mkostemp_safe(char *pattern, int flags);
int open_tmpfile(const char *path, int flags);