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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 22:56:39 -0700 |
| commit | d18f6674bd60e923bcdbf0fd916685b0a250c60f (patch) | |
| tree | 2a97aaa8e9f193e18c8d0d5419fe410b8303c474 | |
| parent | 73a60051379b35a0bec399edfe369c59e50cc775 (diff) | |
| download | postgresql-d18f6674bd60e923bcdbf0fd916685b0a250c60f.tar.gz postgresql-d18f6674bd60e923bcdbf0fd916685b0a250c60f.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 865119d2729..f590ecb25e8 100644 --- a/src/backend/utils/init/miscinit.c +++ b/src/backend/utils/init/miscinit.c @@ -325,6 +325,14 @@ 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 cb8c7450d9b..e155c6ae2fc 100644 --- a/src/bin/initdb/initdb.c +++ b/src/bin/initdb/initdb.c @@ -923,6 +923,9 @@ 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; |