Fix multiple bugs in tablespace symlink removal.

Don't try to examine S_ISLNK(st.st_mode) after a failed lstat().
It's undefined.

Also, if the lstat() reported ENOENT, we do not wish that to be a hard
error, but the code might nonetheless treat it as one (giving an entirely
misleading error message, too) depending on luck-of-the-draw as to what
S_ISLNK() returned.

Don't throw error for ENOENT from rmdir(), either.  (We're not really
expecting ENOENT because we just stat'd the file successfully; but
if we're going to allow ENOENT in the symlink code path, surely the
directory code path should too.)

Generate an appropriate errcode for its-the-wrong-type-of-file complaints.
(ERRCODE_SYSTEM_ERROR doesn't seem appropriate, and failing to write
errcode() around it certainly doesn't work, and not writing an errcode
at all is not per project policy.)

Valgrind noticed the undefined S_ISLNK result; the other problems emerged
while reading the code in the area.

All of this appears to have been introduced in 8f15f74a44f68f9c.
Back-patch to 9.5 where that commit appeared.

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 1ff57285e5949b6a8c80c98c2415ebe66c830dc9..7902d433d552e4b627f975f74167b90c19d95d1d 100644 (file)
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -773,13 +773,26 @@ destroy_tablespace_directories(Oid tablespaceoid, bool redo)
 remove_symlink:
    linkloc = pstrdup(linkloc_with_version_dir);
    get_parent_directory(linkloc);
-   if (lstat(linkloc, &st) == 0 && S_ISDIR(st.st_mode))
+   if (lstat(linkloc, &st) < 0)
+   {
+       int         saved_errno = errno;
+
+       ereport(redo ? LOG : (saved_errno == ENOENT ? WARNING : ERROR),
+               (errcode_for_file_access(),
+                errmsg("could not stat file \"%s\": %m",
+                       linkloc)));
+   }
+   else if (S_ISDIR(st.st_mode))
    {
        if (rmdir(linkloc) < 0)
-           ereport(redo ? LOG : ERROR,
+       {
+           int         saved_errno = errno;
+
+           ereport(redo ? LOG : (saved_errno == ENOENT ? WARNING : ERROR),
                    (errcode_for_file_access(),
                     errmsg("could not remove directory \"%s\": %m",
                            linkloc)));
+       }
    }
 #ifdef S_ISLNK
    else if (S_ISLNK(st.st_mode))
@@ -799,7 +812,7 @@ remove_symlink:
    {
        /* Refuse to remove anything that's not a directory or symlink */
        ereport(redo ? LOG : ERROR,
-               (ERRCODE_SYSTEM_ERROR,
+               (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("\"%s\" is not a directory or symbolic link",
                        linkloc)));
    }
@@ -851,7 +864,7 @@ remove_tablespace_symlink(const char *linkloc)
 {
    struct stat st;
 
-   if (lstat(linkloc, &st) != 0)
+   if (lstat(linkloc, &st) < 0)
    {
        if (errno == ENOENT)
            return;
@@ -863,10 +876,10 @@ remove_tablespace_symlink(const char *linkloc)
    if (S_ISDIR(st.st_mode))
    {
        /*
-        * This will fail if the directory isn't empty, but not
-        * if it's a junction point.
+        * This will fail if the directory isn't empty, but not if it's a
+        * junction point.
         */
-       if (rmdir(linkloc) < 0)
+       if (rmdir(linkloc) < 0 && errno != ENOENT)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not remove directory \"%s\": %m",
@@ -878,7 +891,7 @@ remove_tablespace_symlink(const char *linkloc)
        if (unlink(linkloc) < 0 && errno != ENOENT)
            ereport(ERROR,
                    (errcode_for_file_access(),
-                       errmsg("could not remove symbolic link \"%s\": %m",
+                    errmsg("could not remove symbolic link \"%s\": %m",
                            linkloc)));
    }
 #endif
@@ -886,7 +899,8 @@ remove_tablespace_symlink(const char *linkloc)
    {
        /* Refuse to remove anything that's not a directory or symlink */
        ereport(ERROR,
-               (errmsg("\"%s\" is not a directory or symbolic link",
+               (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+                errmsg("\"%s\" is not a directory or symbolic link",
                        linkloc)));
    }
 }