Horton

Thread

Commits

  1. Fix incorrect initialization of BackendActivityBuffer.

  2. Try to log current the query string when a backend crashes.

  1. BUG #15312: Possible access to unintended variable in "postgres/src/backend/postmaster/pgstat.c" line 2698

    The Post Office <noreply@postgresql.org> — 2018-08-07T10:52:10Z

    The following bug has been logged on the website:

Bug reference:      15312
Logged by:          Petru-Florin Mihancea
Email address:      petrum@gmail.com
PostgreSQL version: Unsupported/Unknown
Operating system:   Macosx
Description:        

While experimenting with a CodeSonar plugin we develop, we noticed a
potential bug in file "postgres/src/backend/postmaster/pgstat.c" line 2698
function CreateSharedBackendStatus.

/* Create or attach to the shared activity buffer */
BackendActivityBufferSize = mul_size(pgstat_track_activity_query_size,
									 NumBackendStatSlots);
BackendActivityBuffer = (char *)
	ShmemInitStruct("Backend Activity Buffer",
					BackendActivityBufferSize,
					&found);
if (!found)
{
	MemSet(BackendActivityBuffer, 0, size); //HERE

	/* Initialize st_activity pointers. */
	buffer = BackendActivityBuffer;
	for (i = 0; i < NumBackendStatSlots; i++)
	{
		BackendStatusArray[i].st_activity_raw = buffer;
		buffer += pgstat_track_activity_query_size;
	}
}

Shouldn't BackendActivityBufferSize be accessed in the marked line instead
of size? 

Thanks,
Petru Florin Mihancea

  2. Re: BUG #15312: Possible access to unintended variable in "postgres/src/backend/postmaster/pgstat.c" line 2698

    Alvaro Herrera <alvherre@2ndquadrant.com> — 2018-08-07T15:31:21Z

    On 2018-Aug-07, PG Bug reporting form wrote:

> While experimenting with a CodeSonar plugin we develop, we noticed a
> potential bug in file "postgres/src/backend/postmaster/pgstat.c" line 2698
> function CreateSharedBackendStatus.

Hmm, yeah this is a bug, introduced by commit c8e8b5a6e20b AFAICS.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

  3. Re: BUG #15312: Possible access to unintended variable in "postgres/src/backend/postmaster/pgstat.c" line 2698

    Tom Lane <tgl@sss.pgh.pa.us> — 2018-08-07T18:45:22Z

    =?utf-8?q?PG_Bug_reporting_form?= <noreply@postgresql.org> writes:
> 	MemSet(BackendActivityBuffer, 0, size); //HERE

> Shouldn't BackendActivityBufferSize be accessed in the marked line instead
> of size? 

Yeah, I think you're right --- looks like a pretty obvious copy-and-paste
oversight.  It's probably harmless as long as
pgstat_track_activity_query_size is at least NAMEDATALEN, but it's
not good.

Thanks for reporting that!

			regards, tom lane