linux-kernel - [PATCH] clk: prevent erronous parsing of children during rate change

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: <1408628866-32351-1-git-send-email-t-kristo@ti.com>
Date:	Thu, 21 Aug 2014 16:47:45 +0300
From:	Tero Kristo <t-kristo@...com>
To:	<linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<tony@...mide.com>, <nm@...com>, <mturquette@...aro.org>
CC:	<linux-arm-kernel@...ts.infradead.org>
Subject: [PATCH] clk: prevent erronous parsing of children during rate change

In some cases, clocks can switch their parent with clk_set_rate, for
example clk_mux can do this in some cases. Current implementation of
clk_change_rate uses un-safe list iteration on the clock children, which
will cause wrong clocks to be parsed in case any of the clock children
change their parents during the change rate operation. Fixed by using
the safe list iterator instead.

The problem was detected due to some divide by zero errors generated
by clock init on dra7-evm board, see discussion under
http://article.gmane.org/gmane.linux.ports.arm.kernel/349180 for details.

Signed-off-by: Tero Kristo <t-kristo@...com>
To: Mike Turquette <mturquette@...aro.org>
Reported-by: Nishanth Menon <nm@...com>
---
 drivers/clk/clk.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b76fa69..bacc06f 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1467,6 +1467,7 @@ static struct clk *clk_propagate_rate_change(struct clk *clk, unsigned long even
 static void clk_change_rate(struct clk *clk)
 {
 	struct clk *child;
+	struct hlist_node *tmp;
 	unsigned long old_rate;
 	unsigned long best_parent_rate = 0;
 	bool skip_set_rate = false;
@@ -1502,7 +1503,11 @@ static void clk_change_rate(struct clk *clk)
 	if (clk->notifier_count && old_rate != clk->rate)
 		__clk_notify(clk, POST_RATE_CHANGE, old_rate, clk->rate);
 
-	hlist_for_each_entry(child, &clk->children, child_node) {
+	/*
+	 * Use safe iteration, as change_rate can actually swap parents
+	 * for certain clock types.
+	 */
+	hlist_for_each_entry_safe(child, tmp, &clk->children, child_node) {
 		/* Skip children who will be reparented to another clock */
 		if (child->new_parent && child->new_parent != clk)
 			continue;
-- 
1.7.9.5

--
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/