Fix incorrect initialization of BackendActivityBuffer.

tglsfdc · tglsfdc · commit 41db97399d6b · 2018-08-07T16:00:44.000-04:00
Since commit c8e8b5a, this has been zeroed out using the wrong length. In practice the length would always be too small, leading to not zeroing the whole buffer rather than clobbering additional memory; and that's pretty harmless, both because shmem would likely start out as zeroes and because we'd reinitialize any given entry before use. Still, it's bogus, so fix it. Reported by Petru-Florin Mihancea (bug #15312) Discussion: https://postgr.es/m/153363913073.1303.6518849192351268091@wrigleys.postgresql.org
diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
@@ -2695,7 +2695,7 @@ CreateSharedBackendStatus(void)
 
 	if (!found)
 	{
-		MemSet(BackendActivityBuffer, 0, size);
+		MemSet(BackendActivityBuffer, 0, BackendActivityBufferSize);
 
 		/* Initialize st_activity pointers. */
 		buffer = BackendActivityBuffer;

Original file line number	Diff line number	Diff line change
`@@ -2695,7 +2695,7 @@ CreateSharedBackendStatus(void)`
`2695`	`2695`
`2696`	`2696`	`if (!found)`
`2697`	`2697`	`{`
`2698`		`- MemSet(BackendActivityBuffer, 0, size);`
	`2698`	`+ MemSet(BackendActivityBuffer, 0, BackendActivityBufferSize);`
`2699`	`2699`
`2700`	`2700`	`/* Initialize st_activity pointers. */`
`2701`	`2701`	`buffer = BackendActivityBuffer;`