linux-kernel - [PATCH 35/91] svcrpc: fix list-corrupting race on nfsd shutdown

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

Message-Id: <20120205220950.939819397@pcw.home.local>
Date:	Sun, 05 Feb 2012 23:10:24 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	gnb@...h.org, "J. Bruce Fields" <bfields@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>
Subject: [PATCH 35/91] svcrpc: fix list-corrupting race on nfsd shutdown

2.6.27-longterm review patch.  If anyone has any objections, please let us know.

------------------

commit ebc63e531cc6a457595dd110b07ac530eae788c3 upstream.

After commit 3262c816a3d7fb1eaabce633caa317887ed549ae "[PATCH] knfsd:
split svc_serv into pools", svc_delete_xprt (then svc_delete_socket) no
longer removed its xpt_ready (then sk_ready) field from whatever list it
was on, noting that there was no point since the whole list was about to
be destroyed anyway.

That was mostly true, but forgot that a few svc_xprt_enqueue()'s might
still be hanging around playing with the about-to-be-destroyed list, and
could get themselves into trouble writing to freed memory if we left
this xprt on the list after freeing it.

(This is actually functionally identical to a patch made first by Ben
Greear, but with more comments.)

Cc: gnb@...h.org
Reported-by: Ben Greear <greearb@...delatech.com>
Tested-by: Ben Greear <greearb@...delatech.com>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 net/sunrpc/svc_xprt.c |   11 ++++++-----
 1 files changed, 6 insertions(+), 5 deletions(-)

Index: longterm-2.6.27/net/sunrpc/svc_xprt.c
===================================================================
--- longterm-2.6.27.orig/net/sunrpc/svc_xprt.c	2012-02-05 22:34:33.947915241 +0100
+++ longterm-2.6.27/net/sunrpc/svc_xprt.c	2012-02-05 22:34:39.823917910 +0100
@@ -830,12 +830,13 @@
 	if (!test_and_set_bit(XPT_DETACHED, &xprt->xpt_flags))
 		list_del_init(&xprt->xpt_list);
 	/*
-	 * We used to delete the transport from whichever list
-	 * it's sk_xprt.xpt_ready node was on, but we don't actually
-	 * need to.  This is because the only time we're called
-	 * while still attached to a queue, the queue itself
-	 * is about to be destroyed (in svc_destroy).
+	 * The only time we're called while xpt_ready is still on a list
+	 * is while the list itself is about to be destroyed (in
+	 * svc_destroy).  BUT svc_xprt_enqueue could still be attempting
+	 * to add new entries to the sp_sockets list, so we can't leave
+	 * a freed xprt on it.
 	 */
+	list_del_init(&xprt->xpt_ready);
 	if (test_bit(XPT_TEMP, &xprt->xpt_flags))
 		serv->sv_tmpcnt--;
 


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/