From 2d33cf7b8b699ea0158e27f3b8182b0731f6273b Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 19 Apr 2025 16:37:42 -0400 Subject: [PATCH] Be more wary of corrupt data in pageinspect's heap_page_items(). The original intent in heap_page_items() was to return nulls, not throw an error or crash, if an item was sufficiently corrupt that we couldn't safely extract data from it. However, commit d6061f83a utterly missed that memo, and not only put in an un-length-checked copy of the tuple's data section, but also managed to break the check on sane nulls-bitmap length. Either mistake could possibly lead to a SIGSEGV crash if the tuple is corrupt. Bug: #18896 Reported-by: Dmitry Kovalenko Author: Dmitry Kovalenko Reviewed-by: Tom Lane Discussion: https://postgr.es/m/18896-add267b8e06663e3@postgresql.org Backpatch-through: 13 --- contrib/pageinspect/heapfuncs.c | 43 ++++++++++++++++++++------------- 1 file changed, 26 insertions(+), 17 deletions(-) diff --git a/contrib/pageinspect/heapfuncs.c b/contrib/pageinspect/heapfuncs.c index 0c2e639131c..e8f43b8bdbf 100644 --- a/contrib/pageinspect/heapfuncs.c +++ b/contrib/pageinspect/heapfuncs.c @@ -212,11 +212,8 @@ heap_page_items(PG_FUNCTION_ARGS) lp_offset + lp_len <= raw_page_size) { HeapTupleHeader tuphdr; - bytea *tuple_data_bytea; - int tuple_data_len; /* Extract information from the tuple header */ - tuphdr = (HeapTupleHeader) PageGetItem(page, id); values[4] = UInt32GetDatum(HeapTupleHeaderGetRawXmin(tuphdr)); @@ -228,31 +225,32 @@ heap_page_items(PG_FUNCTION_ARGS) values[9] = UInt32GetDatum(tuphdr->t_infomask); values[10] = UInt8GetDatum(tuphdr->t_hoff); - /* Copy raw tuple data into bytea attribute */ - tuple_data_len = lp_len - tuphdr->t_hoff; - tuple_data_bytea = (bytea *) palloc(tuple_data_len + VARHDRSZ); - SET_VARSIZE(tuple_data_bytea, tuple_data_len + VARHDRSZ); - memcpy(VARDATA(tuple_data_bytea), (char *) tuphdr + tuphdr->t_hoff, - tuple_data_len); - values[13] = PointerGetDatum(tuple_data_bytea); - /* * We already checked that the item is completely within the raw * page passed to us, with the length given in the line pointer. - * Let's check that t_hoff doesn't point over lp_len, before using - * it to access t_bits and oid. + * But t_hoff could be out of range, so check it before relying on + * it to fetch additional info. */ if (tuphdr->t_hoff >= SizeofHeapTupleHeader && tuphdr->t_hoff <= lp_len && tuphdr->t_hoff == MAXALIGN(tuphdr->t_hoff)) { + int tuple_data_len; + bytea *tuple_data_bytea; + + /* Copy null bitmask and OID, if present */ if (tuphdr->t_infomask & HEAP_HASNULL) { - int bits_len; + int bitmaplen; - bits_len = - BITMAPLEN(HeapTupleHeaderGetNatts(tuphdr)) * BITS_PER_BYTE; - values[11] = CStringGetTextDatum(bits_to_text(tuphdr->t_bits, bits_len)); + bitmaplen = BITMAPLEN(HeapTupleHeaderGetNatts(tuphdr)); + /* better range-check the attribute count, too */ + if (bitmaplen <= tuphdr->t_hoff - SizeofHeapTupleHeader) + values[11] = + CStringGetTextDatum(bits_to_text(tuphdr->t_bits, + bitmaplen * BITS_PER_BYTE)); + else + nulls[11] = true; } else nulls[11] = true; @@ -261,11 +259,22 @@ heap_page_items(PG_FUNCTION_ARGS) values[12] = HeapTupleHeaderGetOidOld(tuphdr); else nulls[12] = true; + + /* Copy raw tuple data into bytea attribute */ + tuple_data_len = lp_len - tuphdr->t_hoff; + tuple_data_bytea = (bytea *) palloc(tuple_data_len + VARHDRSZ); + SET_VARSIZE(tuple_data_bytea, tuple_data_len + VARHDRSZ); + if (tuple_data_len > 0) + memcpy(VARDATA(tuple_data_bytea), + (char *) tuphdr + tuphdr->t_hoff, + tuple_data_len); + values[13] = PointerGetDatum(tuple_data_bytea); } else { nulls[11] = true; nulls[12] = true; + nulls[13] = true; } } else