linux-kernel - [PATCH] bcache: safeguard a dangerous addressing in closure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20171012143737.24577-1-liangchen.linux@gmail.com>
Date:   Thu, 12 Oct 2017 22:37:37 +0800
From:   Liang Chen <liangchen.linux@...il.com>
To:     linux-bcache@...r.kernel.org
Cc:     mlyle@...e.org, i@...y.li, kent.overstreet@...il.com,
        linux-kernel@...r.kernel.org,
        Liang Chen <liangchen.linux@...il.com>
Subject: [PATCH] bcache: safeguard a dangerous addressing in closure_queue

The use of the union reduces the size of closure struct by taking advantage
of the current size of its members. The offset of func in work_struct equals
the size of the first three members, so that work.work_func will just
reference the forth member - fn.

This is smart but dangerous. It can be broken if work_struct or the other
structs get changed, and can be a bit difficult to debug.

Signed-off-by: Liang Chen <liangchen.linux@...il.com>
---
Replacing all occurences of closure_fn to work_func_fn seems to be an option
but that would end up with a big lenghty and error prone patch.

 drivers/md/bcache/closure.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h
index 295b7e4..dbff8f4 100644
--- a/drivers/md/bcache/closure.h
+++ b/drivers/md/bcache/closure.h
@@ -251,6 +251,11 @@ static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
 static inline void closure_queue(struct closure *cl)
 {
 	struct workqueue_struct *wq = cl->wq;
+	/**
+	 * Changes made to closure, work_struct, or a couple of other structs
+	 * may cause work.func not pointing to the right location.
+	 */
+	BUG_ON((unsigned long)cl->fn != (unsigned long)cl->work.func);
 	if (wq) {
 		INIT_WORK(&cl->work, cl->work.func);
 		BUG_ON(!queue_work(wq, &cl->work));
-- 
1.8.3.1