[PATCH 5.11 166/210] clk: fix invalid usage of list cursor in register

Greg Kroah-Hartman
2021-04-12T09:43:36Z

From: Lukasz Bartosik <lb@semihalf.com>

[ Upstream commit 8d3c0c01cb2e36b2bf3c06a82b18b228d0c8f5d0 ]

Fix invalid usage of a list_for_each_entry cursor in
clk_notifier_register(). 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 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/20210401225149.18826-1-lb@semihalf.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/clk/clk.c | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 8c1d04db990d..e08274020944 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -4336,20 +4336,19 @@ int clk_notifier_register(struct clk *clk, struct notifier_block *nb)
/* search the list of notifiers for this clk */
list_for_each_entry(cn, &clk_notifier_list, node)
if (cn->clk == clk)
- break;
+ goto found;

/* if clk wasn't in the notifier list, allocate new clk_notifier */
- if (cn->clk != clk) {
- cn = kzalloc(sizeof(*cn), GFP_KERNEL);
- if (!cn)
- goto out;
+ cn = kzalloc(sizeof(*cn), GFP_KERNEL);
+ if (!cn)
+ goto out;

- cn->clk = clk;
- srcu_init_notifier_head(&cn->notifier_head);
+ cn->clk = clk;
+ srcu_init_notifier_head(&cn->notifier_head);

- list_add(&cn->node, &clk_notifier_list);
- }
+ list_add(&cn->node, &clk_notifier_list);

+found:
ret = srcu_notifier_chain_register(&cn->notifier_head, nb);

clk->core->notifier_count++;
--
2.30.2