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| author | Noah Misch <noah@leadboat.com> | 2018-09-23 22:56:39 -0700 |
|---|---|---|
| committer | Noah Misch <noah@leadboat.com> | 2018-09-23 22:56:42 -0700 |
| commit | 89f2b64da370e7b0737760e3282f096591d6518f (patch) | |
| tree | 29a9ab29cc2c712a74f6f892e00ac71b759a0d94 | |
| parent | b1356f18b70e566da5acd9544632db7b196b3220 (diff) | |
| download | postgresql-89f2b64da370e7b0737760e3282f096591d6518f.tar.gz postgresql-89f2b64da370e7b0737760e3282f096591d6518f.zip | |
Initialize random() in bootstrap/stand-alone postgres and in initdb.
This removes a difference between the standard IsUnderPostmaster
execution environment and that of --boot and --single. In a stand-alone
backend, "SELECT random()" always started at the same seed.
On a system capable of using posix shared memory, initdb could still
conclude "selecting dynamic shared memory implementation ... sysv".
Crashed --boot or --single postgres processes orphaned shared memory
objects having names that collided with the not-actually-random names
that initdb probed. The sysv fallback appeared after ten crashes of
--boot or --single postgres. Since --boot and --single are rare in
production use, systems used for PostgreSQL development are the
principal candidate to notice this symptom.
Back-patch to 9.3 (all supported versions). PostgreSQL 9.4 introduced
dynamic shared memory, but 9.3 does share the "SELECT random()" problem.
Reviewed by Tom Lane and Kyotaro HORIGUCHI.
Discussion: https://postgr.es/m/20180915221546.GA3159382@rfd.leadboat.com
| -rw-r--r-- | src/backend/utils/init/miscinit.c | 8 | ||||
| -rw-r--r-- | src/bin/initdb/initdb.c | 3 |
2 files changed, 11 insertions, 0 deletions
diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c index 03b28c3604a..98c2c1949d4 100644 --- a/src/backend/utils/init/miscinit.c +++ b/src/backend/utils/init/miscinit.c @@ -320,6 +320,14 @@ InitStandaloneProcess(const char *argv0) MyStartTime = time(NULL); /* set our start time in case we call elog */ + /* + * Initialize random() for the first time, like PostmasterMain() would. + * In a regular IsUnderPostmaster backend, BackendRun() computes a + * high-entropy seed before any user query. Fewer distinct initial seeds + * can occur here. + */ + srandom((unsigned int) (MyProcPid ^ MyStartTime)); + /* Initialize process-local latch support */ InitializeLatchSupport(); MyLatch = &LocalLatchData; diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c index ae22e7d9fb8..a9bbc8985ea 100644 --- a/src/bin/initdb/initdb.c +++ b/src/bin/initdb/initdb.c @@ -922,6 +922,9 @@ choose_dsm_implementation(void) #ifdef HAVE_SHM_OPEN int ntries = 10; + /* Initialize random(); this function is its only user in this program. */ + srandom((unsigned int) (getpid() ^ time(NULL))); + while (ntries > 0) { uint32 handle; |