Fix datalen calculation in tsvectorrecv().

tglsfdc · tglsfdc · commit 5b7b3824648d · 2023-10-01T13:16:47.000-04:00
After receiving position data for a lexeme, tsvectorrecv() advanced its "datalen" value by (npos+1)*sizeof(WordEntry) where the correct calculation is (npos+1)*sizeof(WordEntryPos). This accidentally failed to render the constructed tsvector invalid, but it did result in leaving some wasted space approximately equal to the space consumed by the position data. That could have several bad effects: * Disk space is wasted if the received tsvector is stored into a table as-is. * A legal tsvector could get rejected with "maximum total lexeme length exceeded" if the extra space pushes it over the MAXSTRPOS limit. * In edge cases, the finished tsvector could be assigned a length larger than the allocated size of its palloc chunk, conceivably leading to SIGSEGV when the tsvector gets copied somewhere else. The odds of a field failure of this sort seem low, though valgrind testing could probably have found this. While we're here, let's express the calculation as "sizeof(uint16) + npos * sizeof(WordEntryPos)" to avoid the type pun implicit in the "npos + 1" formulation. It's not wrong given that WordEntryPos had better be 2 bytes to avoid padding problems, but it seems clearer this way. Report and patch by Denis Erokhin. Back-patch to all supported versions. Discussion: https://postgr.es/m/009801d9f2d9$f29730c0$d7c59240$@datagile.ru
diff --git a/src/backend/utils/adt/tsvector.c b/src/backend/utils/adt/tsvector.c
@@ -498,7 +498,7 @@ tsvectorrecv(PG_FUNCTION_ARGS)
 		 * But make sure the buffer is large enough first.
 		 */
 		while (hdrlen + SHORTALIGN(datalen + lex_len) +
-			   (npos + 1) * sizeof(WordEntryPos) >= len)
+			   sizeof(uint16) + npos * sizeof(WordEntryPos) >= len)
 		{
 			len *= 2;
 			vec = (TSVector) repalloc(vec, len);
@@ -544,7 +544,7 @@ tsvectorrecv(PG_FUNCTION_ARGS)
 					elog(ERROR, "position information is misordered");
 			}
 
-			datalen += (npos + 1) * sizeof(WordEntry);
+			datalen += sizeof(uint16) + npos * sizeof(WordEntryPos);
 		}
 	}
 

Original file line number	Diff line number	Diff line change
`@@ -498,7 +498,7 @@ tsvectorrecv(PG_FUNCTION_ARGS)`
`498`	`498`	`* But make sure the buffer is large enough first.`
`499`	`499`	`*/`
`500`	`500`	`while (hdrlen + SHORTALIGN(datalen + lex_len) +`
`501`		`- (npos + 1) * sizeof(WordEntryPos) >= len)`
	`501`	`+ sizeof(uint16) + npos * sizeof(WordEntryPos) >= len)`
`502`	`502`	`{`
`503`	`503`	`len *= 2;`
`504`	`504`	`vec = (TSVector) repalloc(vec, len);`
`@@ -544,7 +544,7 @@ tsvectorrecv(PG_FUNCTION_ARGS)`
`544`	`544`	`elog(ERROR, "position information is misordered");`
`545`	`545`	`}`
`546`	`546`
`547`		`- datalen += (npos + 1) * sizeof(WordEntry);`
	`547`	`+ datalen += sizeof(uint16) + npos * sizeof(WordEntryPos);`
`548`	`548`	`}`
`549`	`549`	`}`
`550`	`550`