[PATCH 5.11 167/210] clk: fix invalid usage of list cursor in unregister

Greg Kroah-Hartman
2021-04-12T09:43:34Z

From: Lukasz Bartosik <lb@semihalf.com>

[ Upstream commit 7045465500e465b09f09d6e5bdc260a9f1aab97b ]

Fix invalid usage of a list_for_each_entry cursor in
clk_notifier_unregister(). When list is empty or if the list
is completely traversed (without breaking from the loop on one
of the entries) then the list cursor does not point to a valid
entry and therefore should not be used. The patch fixes a logical
bug that hasn't been seen in pratice however it is analogus
to the bug fixed in clk_notifier_register().

The issue was dicovered when running 5.12-rc1 kernel on x86_64
with KASAN enabled:
BUG: KASAN: global-out-of-bounds in clk_notifier_register+0xab/0x230
Read of size 8 at addr ffffffffa0d10588 by task swapper/0/1

CPU: 1 PID: 1 Comm: swapper/0 Not tainted 5.12.0-rc1 #1
Hardware name: Google Caroline/Caroline,
BIOS Google_Caroline.7820.430.0 07/20/2018
Call Trace:
dump_stack+0xee/0x15c
print_address_description+0x1e/0x2dc
kasan_report+0x188/0x1ce
? clk_notifier_register+0xab/0x230
? clk_prepare_lock+0x15/0x7b
? clk_notifier_register+0xab/0x230
clk_notifier_register+0xab/0x230
dw8250_probe+0xc01/0x10d4
...
Memory state around the buggy address:
ffffffffa0d10480: 00 00 00 00 00 03 f9 f9 f9 f9 f9 f9 00 00 00 00
ffffffffa0d10500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9
>ffffffffa0d10580: f9 f9 f9 f9 00 00 00 00 00 00 00 00 00 00 00 00
^
ffffffffa0d10600: 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9 00 00 00 00
ffffffffa0d10680: 00 00 00 00 00 00 00 00 f9 f9 f9 f9 00 00 00 00
==================================================================

Fixes: b2476490ef11 ("clk: introduce the common clock framework")
Reported-by: Lukasz Majczak <lma@semihalf.com>
Signed-off-by: Lukasz Bartosik <lb@semihalf.com>
Link: https://lore.kernel.org/r/20210401225149.18826-2-lb@semihalf.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/clk/clk.c | 30 +++++++++++++-----------------
1 file changed, 13 insertions(+), 17 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index e08274020944..571ae066e548 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -4373,32 +4373,28 @@ EXPORT_SYMBOL_GPL(clk_notifier_register);
*/
int clk_notifier_unregister(struct clk *clk, struct notifier_block *nb)
{
- struct clk_notifier *cn = NULL;
- int ret = -EINVAL;
+ struct clk_notifier *cn;
+ int ret = -ENOENT;

if (!clk || !nb)
return -EINVAL;

clk_prepare_lock();

- list_for_each_entry(cn, &clk_notifier_list, node)
- if (cn->clk == clk)
- break;
-
- if (cn->clk == clk) {
- ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);
+ list_for_each_entry(cn, &clk_notifier_list, node) {
+ if (cn->clk == clk) {
+ ret = srcu_notifier_chain_unregister(&cn->notifier_head, nb);

- clk->core->notifier_count--;
+ clk->core->notifier_count--;

- /* XXX the notifier code should handle this better */
- if (!cn->notifier_head.head) {
- srcu_cleanup_notifier_head(&cn->notifier_head);
- list_del(&cn->node);
- kfree(cn);
+ /* XXX the notifier code should handle this better */
+ if (!cn->notifier_head.head) {
+ srcu_cleanup_notifier_head(&cn->notifier_head);
+ list_del(&cn->node);
+ kfree(cn);
+ }
+ break;
}
-
- } else {
- ret = -ENOENT;
}

clk_prepare_unlock();
--
2.30.2