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postgres_fdw: Replace buffers in RemoteAttributeMapping with pointers.

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Commit 28972b6fc ("Add support for importing statistics from remote
servers.") stored the names of local/remote columns for a foreign table
into the buffers of NAMEDATALEN bytes in this structure, without
accounting for the possibility that the remote column name in particular
could be longer than NAMEDATALEN - 1.  If it was longer than that, this
would leave it unterminated/truncated in the buffer, invoking undefined
behavior when match_attrmap() processes it, which assumes that it's
fully-contained/terminated in the buffer.

To fix, replace the buffers with char pointers, pstrdup the local/remote
column names, and store the results into the pointers.  This commit also
adds a function to clean up the nested data structure.

Per Coverity and Tom Lane.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Author: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Etsuro Fujita <etsuro.fujita@gmail.com>
Discussion: https://postgr.es/m/342868.1776017700%40sss.pgh.pa.us
This commit is contained in:
Etsuro Fujita 2026-05-16 17:55:00 +09:00
parent 8eba2edb80
commit aa1f93a338
1 changed files with 26 additions and 6 deletions
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32
contrib/postgres_fdw/postgres_fdw.c
View file

@ -325,8 +325,8 @@ typedef struct
typedef struct
{
AttrNumber local_attnum;
char local_attname[NAMEDATALEN];
char remote_attname[NAMEDATALEN];
char *local_attname;
char *remote_attname;
int res_index;
} RemoteAttributeMapping;
@ -704,6 +704,7 @@ static PGresult *fetch_attstats(PGconn *conn, int server_version_num,
const char *column_list);
static RemoteAttributeMapping *build_remattrmap(Relation relation, List *va_cols,
int *p_attrcnt, StringInfo column_list);
static void free_remattrmap(RemoteAttributeMapping *map, int len);
static bool attname_in_list(const char *attname, List *va_cols);
static int remattrmap_cmp(const void *v1, const void *v2);
static bool match_attrmap(PGresult *res,
@ -5670,8 +5671,7 @@ postgresImportForeignStatistics(Relation relation, List *va_cols, int elevel)
PQclear(remstats.rel);
PQclear(remstats.att);
if (remattrmap)
pfree(remattrmap);
free_remattrmap(remattrmap, attrcnt);
return ok;
}
@ -5957,8 +5957,8 @@ build_remattrmap(Relation relation, List *va_cols,
deparseStringLiteral(column_list, remote_attname);
remattrmap[attrcnt].local_attnum = attnum;
strncpy(remattrmap[attrcnt].local_attname, attname, NAMEDATALEN);
strncpy(remattrmap[attrcnt].remote_attname, remote_attname, NAMEDATALEN);
remattrmap[attrcnt].local_attname = pstrdup(attname);
remattrmap[attrcnt].remote_attname = pstrdup(remote_attname);
remattrmap[attrcnt].res_index = -1;
attrcnt++;
}
@ -5972,6 +5972,26 @@ build_remattrmap(Relation relation, List *va_cols,
return remattrmap;
}
/*
* Free the structure created by build_remattrmap().
*/
static void
free_remattrmap(RemoteAttributeMapping *map, int len)
{
if (!map)
return;
for (int i = 0; i < len; i++)
{
Assert(map[i].local_attname);
pfree(map[i].local_attname);
Assert(map[i].remote_attname);
pfree(map[i].remote_attname);
}
pfree(map);
}
/*
* Test if an attribute name is in the list.
*