Add failsafe against duplicate UUID's generated by threaded programs

Add in randomness based on Linux's thread id (gettid) to avoid race
conditions when two threads try to generate uuid's at the same time.
This shouldn't be an issue if /dev/urandom has proper locking and is
present, so this is just a failsafe.

Addresses SourceForge Bug: #1529672

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/ChangeLog b/ChangeLog
index b416349..f0f5641 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,7 @@
 2006-10-22  Theodore Tso  <tytso@mit.edu>
 
+       * configure, configure.in: Add test for jrand48()
+
        * MCONFIG.in: Add datarootdir definition for compatibility with
                autoconf 2.60.
 

diff --git a/configure b/configure
index a3008ef..a0aae22 100755 (executable)
--- a/configure
+++ b/configure
@@ -16306,7 +16306,8 @@ fi
 
 
 
-for ac_func in chflags getrusage llseek lseek64 open64 fstat64 getmntinfo strtoull strcasecmp srandom fchown mallinfo fdatasync strnlen strptime sysconf pathconf posix_memalign memalign valloc __secure_getenv prctl
+
+for ac_func in chflags getrusage llseek lseek64 open64 fstat64 getmntinfo strtoull strcasecmp srandom jrand48 fchown mallinfo fdatasync strnlen strptime sysconf pathconf posix_memalign memalign valloc __secure_getenv prctl
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 { echo "$as_me:$LINENO: checking for $ac_func" >&5

diff --git a/configure.in b/configure.in
index c78d03d..068d6ed 100644 (file)
--- a/configure.in
+++ b/configure.in
@@ -659,7 +659,7 @@ AC_CHECK_MEMBER(struct sockaddr.sa_len,
        [#include <sys/types.h>
         #include <sys/socket.h>])
 dnl
-AC_CHECK_FUNCS(chflags getrusage llseek lseek64 open64 fstat64 getmntinfo strtoull strcasecmp srandom fchown mallinfo fdatasync strnlen strptime sysconf pathconf posix_memalign memalign valloc __secure_getenv prctl)
+AC_CHECK_FUNCS(chflags getrusage llseek lseek64 open64 fstat64 getmntinfo strtoull strcasecmp srandom jrand48 fchown mallinfo fdatasync strnlen strptime sysconf pathconf posix_memalign memalign valloc __secure_getenv prctl)
 dnl
 dnl Check to see if -lsocket is required (solaris) to make something
 dnl that uses socket() to compile; this is needed for the UUID library

diff --git a/lib/uuid/ChangeLog b/lib/uuid/ChangeLog
index 1a1a9e8..d51b999 100644 (file)
--- a/lib/uuid/ChangeLog
+++ b/lib/uuid/ChangeLog
@@ -1,3 +1,12 @@
+2006-10-22  Theodore Tso  <tytso@mit.edu>
+
+       * gen_uuid.c (get_random_bytes): Add in randomness based on
+               Linux's thread id (gettid) to avoid race conditions when
+               two threads try to generate uuid's at the same time.  This
+               shouldn't be an issue if /dev/urandom has proper locking
+               and is present, so this is just a failsafe.  (Addresses
+               SourceForge Bug: #1529672)
+
 2006-01-06  Theodore Ts'o  <tytso@mit.edu>
 
        * gen_uuid.c (get_random_fd): Set the FD_CLOEXEC flag on the file

diff --git a/lib/uuid/gen_uuid.c b/lib/uuid/gen_uuid.c
index 421314a..61f2805 100644 (file)
--- a/lib/uuid/gen_uuid.c
+++ b/lib/uuid/gen_uuid.c
@@ -69,6 +69,9 @@
 #ifdef HAVE_NET_IF_DL_H
 #include <net/if_dl.h>
 #endif
+#ifdef __linux__
+#include <sys/syscall.h>
+#endif
 
 #include "uuidP.h"
 
@@ -77,6 +80,11 @@
 #define rand()                 random()
 #endif
 
+#if defined(__linux__) && defined(__NR_gettid) && defined(HAVE_JRAND48)
+#define DO_JRAND_MIX
+static unsigned short jrand_seed[3];
+#endif
+
 static int get_random_fd(void)
 {
        struct timeval  tv;
@@ -94,6 +102,11 @@ static int get_random_fd(void)
                                fcntl(fd, F_SETFD, i | FD_CLOEXEC);
                }
                srand((getpid() << 16) ^ getuid() ^ tv.tv_sec ^ tv.tv_usec);
+#ifdef DO_JRAND_MIX
+               jrand_seed[0] = getpid() ^ (tv.tv_sec & 0xFFFF);
+               jrand_seed[1] = getppid() ^ (tv.tv_usec & 0xFFFF);
+               jrand_seed[2] = (tv.tv_sec ^ tv.tv_usec) >> 16;
+#endif
        }
        /* Crank the random number generator a few times */
        gettimeofday(&tv, 0);
@@ -112,6 +125,7 @@ static void get_random_bytes(void *buf, int nbytes)
        int i, n = nbytes, fd = get_random_fd();
        int lose_counter = 0;
        unsigned char *cp = (unsigned char *) buf;
+       unsigned short tmp_seed[3];
 
        if (fd >= 0) {
                while (n > 0) {
@@ -133,6 +147,15 @@ static void get_random_bytes(void *buf, int nbytes)
         */
        for (cp = buf, i = 0; i < nbytes; i++)
                *cp++ ^= (rand() >> 7) & 0xFF;
+#ifdef DO_JRAND_MIX
+       memcpy(tmp_seed, jrand_seed, sizeof(tmp_seed));
+       jrand_seed[2] = jrand_seed[2] ^ syscall(__NR_gettid);
+       for (cp = buf, i = 0; i < nbytes; i++)
+               *cp++ ^= (jrand48(tmp_seed) >> 7) & 0xFF;
+       memcpy(jrand_seed, tmp_seed, 
+              sizeof(jrand_seed)-sizeof(unsigned short));
+#endif
+
        return;
 }