Thread: pgsql: Avoid memory size overflow when allocating backend activity buff

pgsql: Avoid memory size overflow when allocating backend activity buff

From
Michael Paquier
Date:
Avoid memory size overflow when allocating backend activity buffer

The code in charge of copying the contents of PgBackendStatus to local
memory could fail on memory allocation because of an overflow on the
amount of memory to use.  The overflow can happen when combining a high
value track_activity_query_size (max at 1MB) with a large
max_connections, when both multiplied get higher than INT32_MAX as both
parameters treated as signed integers.  This could for example trigger
with the following functions, all calling pgstat_read_current_status():
- pg_stat_get_backend_subxact()
- pg_stat_get_backend_idset()
- pg_stat_get_progress_info()
- pg_stat_get_activity()
- pg_stat_get_db_numbackends()

The change to use MemoryContextAllocHuge() has been introduced in
8d0ddccec636, so backpatch down to 12.

Author: Jakub Wartak
Discussion: https://postgr.es/m/CAKZiRmw8QSNVw2qNK-dznsatQqz+9DkCquxP0GHbbv1jMkGHMA@mail.gmail.com
Backpatch-through: 12

Branch
------
REL_13_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/a0b0136259080c0441f4ff1c7d65d8a9d08360cf

Modified Files
--------------
src/backend/postmaster/pgstat.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)