Here's a patch to fix a race condition that Dan Hipschman and I
thought of while walking across the courtyard to Boelter Hall at UCLA.
The problem is that a signal can come in while cleanup is running
during a premature exit (e.g., due to an I/O error), causing 'sort' to
unlink a file that has already been unlinked. This might in theory
cause 'sort' to unlink some other process's temp file.
Dan wrote the initial version of the patch and I tweaked it a bit. I
thought it a bit cleaner to have a single cleanup function than
multiple calls to atexit, since we should not invoke some of this
stuff until the signal mask is known.
2007-01-19 Dan Hipschman <[EMAIL PROTECTED]>
and Paul Eggert <[EMAIL PROTECTED]>
* src/sort.c (cleanup): Clear temphead at the end.
(exit_cleanup): New function.
(main): Don't invoke atexit until we're ready.
Invoke it with exit_cleanup, not with cleanup and close_stdout,
to avoid a race condition with cleanup and signal handling.
diff --git a/src/sort.c b/src/sort.c
index f03237c..326866f 100644
--- a/src/sort.c
+++ b/src/sort.c
@@ -417,6 +417,25 @@ cleanup (void)
for (node = temphead; node; node = node->next)
unlink (node->name);
+ temphead = NULL;
+}
+
+/* Cleanup actions to take when exiting. */
+
+static void
+exit_cleanup (void)
+{
+ if (temphead)
+ {
+ /* Clean up any remaining temporary files in a critical section so
+ that a signal handler does not try to clean them too. */
+ sigset_t oldset;
+ sigprocmask (SIG_BLOCK, &caught_signals, &oldset);
+ cleanup ();
+ sigprocmask (SIG_SETMASK, &oldset, NULL);
+ }
+
+ close_stdout ();
}
/* Create a new temporary file, returning its newly allocated name.
@@ -2302,10 +2321,7 @@ main (int argc, char **argv)
bindtextdomain (PACKAGE, LOCALEDIR);
textdomain (PACKAGE);
- atexit (cleanup);
-
initialize_exit_failure (SORT_FAILURE);
- atexit (close_stdout);
hard_LC_COLLATE = hard_locale (LC_COLLATE);
#if HAVE_NL_LANGINFO
@@ -2365,6 +2381,9 @@ main (int argc, char **argv)
#endif
}
+ /* The signal mask is known, so it is safe to invoke exit_cleanup. */
+ atexit (exit_cleanup);
+
gkey.sword = gkey.eword = SIZE_MAX;
gkey.ignore = NULL;
gkey.translate = NULL;
M ChangeLog
M src/sort.c
Committed as 600ef4a9207574c4459963a7948faa67de142e9c
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