From f71007fbb3b83fba21daae9144cc07e205f2365c Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Tue, 25 Oct 2022 15:21:42 +1300 Subject: [PATCH] Fix readlink() for non-PostgreSQL junction points on Windows. Since commit c5cb8f3b taught stat() to follow symlinks, and since initdb uses pg_mkdir_p(), and that examines parent directories, our humble readlink() implementation can now be exposed to junction points not of PostgreSQL origin. Those might be corrupted by our naive path mangling, which doesn't really understand NT paths in general. Simply decline to transform paths that don't look like a drive absolute path. That means that readlink() returns the NT path directly when checking a parent directory of PGDATA that happen to point to a drive using "rooted" format. That works for the purposes of our stat() emulation. Reported-by: Roman Zharkov Reviewed-by: Roman Zharkov Discussion: https://postgr.es/m/4590c37927d7b8ee84f9855d83229018%40postgrespro.ru Discussion: https://postgr.es/m/CA%2BhUKG%2BajSQ_8eu2AogTncOnZ5me2D-Cn66iN_-wZnRjLN%2Bicg%40mail.gmail.com --- src/port/dirmod.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/src/port/dirmod.c b/src/port/dirmod.c index 398787360a2..d83316d6a2a 100644 --- a/src/port/dirmod.c +++ b/src/port/dirmod.c @@ -363,10 +363,21 @@ pgreadlink(const char *path, char *buf, size_t size) r -= 1; /* - * If the path starts with "\??\", which it will do in most (all?) cases, - * strip those out. + * If the path starts with "\??\" followed by a "drive absolute" path + * (known to Windows APIs as RtlPathTypeDriveAbsolute), then strip that + * prefix. This undoes some of the transformation performed by + * pqsymlink(), to get back to a format that users are used to seeing. We + * don't know how to transform other path types that might be encountered + * outside PGDATA, so we just return them directly. */ - if (r > 4 && strncmp(buf, "\\??\\", 4) == 0) + if (r >= 7 && + buf[0] == '\\' && + buf[1] == '?' && + buf[2] == '?' && + buf[3] == '\\' && + isalpha(buf[4]) && + buf[5] == ':' && + buf[6] == '\\') { memmove(buf, buf + 4, strlen(buf + 4) + 1); r -= 4; -- 2.30.2