rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Avoid possibly accessing off the end of memory in examine_attribute(). 

Since the last couple of columns of pg_type are often NULL,
sizeof(FormData_pg_type) can be an overestimate of the actual size of the
tuple data part.  Therefore memcpy'ing that much out of the catalog cache,
as analyze.c was doing, poses a small risk of copying past the end of
memory and incurring SIGSEGV.  No such crash has been identified in the
field, but we've certainly seen the equivalent happen in other code paths,
so patch this one all the way back.

Per valgrind testing by Noah Misch, though this is not his proposed patch.
I chose to use SearchSysCacheCopy1 rather than inventing special-purpose
infrastructure for copying only the minimal part of a pg_type tuple.
This commit is contained in:
Tom Lane 2011-09-06 14:36:01 -04:00
parent 1426abb516
commit 80360976e6
1 changed files with 5 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
src/backend/commands/analyze.c
View File

@ -655,14 +655,12 @@ examine_attribute(Relation onerel, int attnum)
stats = (VacAttrStats *) palloc0(sizeof(VacAttrStats));
stats->attr = (Form_pg_attribute) palloc(ATTRIBUTE_TUPLE_SIZE);
memcpy(stats->attr, attr, ATTRIBUTE_TUPLE_SIZE);
typtuple = SearchSysCache(TYPEOID,
ObjectIdGetDatum(attr->atttypid),
0, 0, 0);
typtuple = SearchSysCacheCopy(TYPEOID,
ObjectIdGetDatum(attr->atttypid),
0, 0, 0);
if (!HeapTupleIsValid(typtuple))
elog(ERROR, "cache lookup failed for type %u", attr->atttypid);
stats->attrtype = (Form_pg_type) palloc(sizeof(FormData_pg_type));
memcpy(stats->attrtype, GETSTRUCT(typtuple), sizeof(FormData_pg_type));
ReleaseSysCache(typtuple);
stats->attrtype = (Form_pg_type) GETSTRUCT(typtuple);
stats->anl_context = anl_context;
stats->tupattnum = attnum;
@ -678,7 +676,7 @@ examine_attribute(Relation onerel, int attnum)
if (!ok || stats->compute_stats == NULL || stats->minrows <= 0)
{
pfree(stats->attrtype);
heap_freetuple(typtuple);
pfree(stats->attr);
pfree(stats);
return NULL;