From 6ed3edc77275aa51d1d0b1012c0a36db65735d39 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Thu, 11 Aug 2022 10:42:13 +1200 Subject: [PATCH v2 1/2] Fix readlink() for general Windows junction points. Our symlink() and readlink() replacements perform a naive transformation from DOS paths to NT paths and back, as required by the junction point APIs. This was enough for the "drive absolute" paths we expect users to provide for tablespaces, for example "d:\my\fast\storage". 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 Discussion: https://postgr.es/m/4590c37927d7b8ee84f9855d83229018%40postgrespro.ru --- src/port/dirmod.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/src/port/dirmod.c b/src/port/dirmod.c index 2818bfd2e9..53310baafb 100644 --- a/src/port/dirmod.c +++ b/src/port/dirmod.c @@ -199,7 +199,11 @@ pgsymlink(const char *oldpath, const char *newpath) if (dirhandle == INVALID_HANDLE_VALUE) return -1; - /* make sure we have an unparsed native win32 path */ + /* + * We expect either an NT path or a "drive absolute" path like "C:\..." + * that we convert to an NT path by bolting on a prefix and converting any + * Unix-style path delimiters to NT-style. + */ if (memcmp("\\??\\", oldpath, 4) != 0) snprintf(nativeTarget, sizeof(nativeTarget), "\\??\\%s", oldpath); else @@ -351,10 +355,21 @@ pgreadlink(const char *path, char *buf, size_t size) } /* - * 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; -- 2.35.1