Re: [PATCH] Fix memory leak in pg_config

Sorry for the formatting in my previous email. Resending in plain text.

Hi,

While testing PostgreSQL with LeakSanitizer enabled, I found a memory
leak in pg_config.

The issue can be reproduced by running:

pg_config --version

LeakSanitizer reports 2829 bytes leaked in 47 allocations. The full
report is attached as leak_sanitizer.txt.

The relevant allocation stack is:

libc.so.6!__GI___libc_malloc(size_t bytes) (malloc.c:3288)
pg_malloc_internal(size_t size, int flags)
(src/common/fe_memutils.c:36)
palloc(Size size)
(src/common/fe_memutils.c:123)
palloc_mul(Size s1, Size s2)
(src/common/fe_memutils.c:312)
get_configdata(const char *my_exec_path, size_t *configdata_len)
(src/common/config_info.c:42)
main(int argc, char **argv)
(src/bin/pg_config/pg_config.c:157)

Although get_configdata() uses palloc_array() and pstrdup(), pg_config
is a frontend program. The frontend implementations of palloc() and
pstrdup() ultimately allocate memory using malloc() and strdup(),
through pg_malloc_internal() and pg_strdup(), respectively. These
allocations are not owned by a backend memory context and therefore
remain allocated until they are explicitly freed or the process exits.

get_configdata() allocates the ConfigData array with palloc_array() and
allocates its name and setting strings with pstrdup(). pg_config does
not release these allocations before exiting.

This leak is harmless for a short-lived process, since the operating
system releases the memory at process termination. However, it causes
LeakSanitizer failures and adds noise to sanitizer-based testing.

The attached patch adds a helper that frees every name and setting
string and then frees the ConfigData array. The helper is called on
every exit path reached after get_configdata().

After applying the patch, pg_config --version completes without a
LeakSanitizer report.

The patch is attached as:

v1-0001-Fix-memory-leak-in-pg_config.patch

--
Best wishes,
Ivan Kush
Tantor Labs LLC