From 3be381a900df75de6a085cc3a465d85ec8bf39cd Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sat, 11 Sep 2021 15:19:31 -0400 Subject: [PATCH] Make pg_regexec() robust against out-of-range search_start. If search_start is greater than the length of the string, we should just return REG_NOMATCH immediately. (Note that the equality case should *not* be rejected, since the pattern might be able to match zero characters.) This guards various internal assumptions that the min of a range of string positions is not more than the max. Violation of those assumptions could allow an attempt to fetch string[search_start-1], possibly causing a crash. Jaime Casanova pointed out that this situation is reachable with the new regexp_xxx functions that accept a user-specified start position. I don't believe it's reachable via any in-core call site in v14 and below. However, extensions could possibly call pg_regexec with an out-of-range search_start, so let's back-patch the fix anyway. Discussion: https://postgr.es/m/20210911180357.GA6870@ahch-to --- src/backend/regex/regexec.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/src/backend/regex/regexec.c b/src/backend/regex/regexec.c index 34381ff8d9..460c987a60 100644 --- a/src/backend/regex/regexec.c +++ b/src/backend/regex/regexec.c @@ -196,6 +196,8 @@ pg_regexec(regex_t *re, return REG_INVARG; if (re->re_csize != sizeof(chr)) return REG_MIXED; + if (search_start > len) + return REG_NOMATCH; /* Initialize locale-dependent support */ pg_set_regex_collation(re->re_collation);