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Add some simple defenses against null fields in pg_largeobject, and add 

comments noting that there's an alignment assumption now that the data
field could be in 1-byte-header format.  Per discussion with Greg Stark.
This commit is contained in:
Tom Lane 2007-06-12 19:46:24 +00:00
parent ee0d34ab64
commit e976fd43c6
1 changed files with 20 additions and 5 deletions
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25
src/backend/storage/large_object/inv_api.c
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@ -5,6 +5,13 @@
* contains the user-level large object application interface routines.
*
*
* Note: we access pg_largeobject.data using its C struct declaration.
* This is safe because it immediately follows pageno which is an int4 field,
* and therefore the data field will always be 4-byte aligned, even if it
* is in the short 1-byte-header format. We have to detoast it since it's
* quite likely to be in compressed or short format. We also need to check
* for NULLs, since initdb will mark loid and pageno but not data as NOT NULL.
*
* Note: many of these routines leak memory in CurrentMemoryContext, as indeed
* does most of the backend code. We expect that CurrentMemoryContext will
* be a short-lived context. Data that must persist across function calls
@ -17,7 +24,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/large_object/inv_api.c,v 1.124 2007/04/06 04:21:42 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/large_object/inv_api.c,v 1.125 2007/06/12 19:46:24 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -330,8 +337,10 @@ inv_getsize(LargeObjectDesc *obj_desc)
bool pfreeit;
found = true;
if (HeapTupleHasNulls(tuple)) /* paranoia */
elog(ERROR, "null field found in pg_largeobject");
data = (Form_pg_largeobject) GETSTRUCT(tuple);
datafield = &(data->data);
datafield = &(data->data); /* see note at top of file */
pfreeit = false;
if (VARATT_IS_EXTENDED(datafield))
{
@ -434,6 +443,8 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
bytea *datafield;
bool pfreeit;
if (HeapTupleHasNulls(tuple)) /* paranoia */
elog(ERROR, "null field found in pg_largeobject");
data = (Form_pg_largeobject) GETSTRUCT(tuple);
/*
@ -457,7 +468,7 @@ inv_read(LargeObjectDesc *obj_desc, char *buf, int nbytes)
off = (int) (obj_desc->offset - pageoff);
Assert(off >= 0 && off < LOBLKSIZE);
datafield = &(data->data);
datafield = &(data->data); /* see note at top of file */
pfreeit = false;
if (VARATT_IS_EXTENDED(datafield))
{
@ -558,6 +569,8 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
{
if ((oldtuple = index_getnext(sd, ForwardScanDirection)) != NULL)
{
if (HeapTupleHasNulls(oldtuple)) /* paranoia */
elog(ERROR, "null field found in pg_largeobject");
olddata = (Form_pg_largeobject) GETSTRUCT(oldtuple);
Assert(olddata->pageno >= pageno);
}
@ -575,7 +588,7 @@ inv_write(LargeObjectDesc *obj_desc, const char *buf, int nbytes)
*
* First, load old data into workbuf
*/
datafield = &(olddata->data);
datafield = &(olddata->data); /* see note at top of file */
pfreeit = false;
if (VARATT_IS_EXTENDED(datafield))
{
@ -737,6 +750,8 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
olddata = NULL;
if ((oldtuple = index_getnext(sd, ForwardScanDirection)) != NULL)
{
if (HeapTupleHasNulls(oldtuple)) /* paranoia */
elog(ERROR, "null field found in pg_largeobject");
olddata = (Form_pg_largeobject) GETSTRUCT(oldtuple);
Assert(olddata->pageno >= pageno);
}
@ -749,7 +764,7 @@ inv_truncate(LargeObjectDesc *obj_desc, int len)
if (olddata != NULL && olddata->pageno == pageno)
{
/* First, load old data into workbuf */
bytea *datafield = &(olddata->data);
bytea *datafield = &(olddata->data); /* see note at top of file */
bool pfreeit = false;
int pagelen;