From: Rich Felker <dalias@aerifal.cx>
Date: Fri, 19 Sep 2014 16:28:45 +0000 (-0400)
Subject: fix linked list corruption in flockfile lists
X-Git-Tag: v1.1.5~14
X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=3e936ce81bbbcc968f576aedbd5203621839f152;p=oweals%2Fmusl.git

fix linked list corruption in flockfile lists

commit 5345c9b884e7c4e73eb2c8bb83b8d0df20f95afb added a linked list to
track the FILE streams currently locked (via flockfile) by a thread.
due to a failure to fully link newly added members, removal from the
list could leave behind references which could later result in writes
to already-freed memory and possibly other memory corruption.

implicit stdio locking was unaffected; the list is only used in
conjunction with explicit flockfile locking.

this bug was not present in any releases; it was introduced and fixed
during the same release cycle.

patch by Timo Teräs, who discovered and tracked down the bug.
---

diff --git a/src/stdio/ftrylockfile.c b/src/stdio/ftrylockfile.c
index 6f9a4b88..eb13c839 100644
--- a/src/stdio/ftrylockfile.c
+++ b/src/stdio/ftrylockfile.c
@@ -34,6 +34,7 @@ int ftrylockfile(FILE *f)
 	f->lockcount = 1;
 	f->prev_locked = 0;
 	f->next_locked = self->stdio_locks;
+	if (f->next_locked) f->next_locked->prev_locked = f;
 	self->stdio_locks = f;
 	return 0;
 }