linux-kernel - [PATCH] clk: spacemit: fix UBSAN warning during probe

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Message-ID: <20251117190329.1337250-1-cmirabil@redhat.com>
Date: Mon, 17 Nov 2025 14:03:29 -0500
From: Charles Mirabile <cmirabil@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: spacemit@...ts.linux.dev,
	linux-riscv@...ts.infradead.org,
	linux-clk@...r.kernel.org,
	mturquette@...libre.com,
	sboyd@...nel.org,
	dlan@...too.org,
	heylenay@....org,
	elder@...cstar.com,
	troy.mitchell@...ux.spacemit.com,
	inochiama@...look.com,
	Charles Mirabile <cmirabil@...hat.com>,
	Yanko Kaneti <yaneti@...lera.com>
Subject: [PATCH] clk: spacemit: fix UBSAN warning during probe

When booting with KASAN enabled the following splat is encountered during
probe of the k1 clock driver:

UBSAN: array-index-out-of-bounds in drivers/clk/spacemit/ccu-k1.c:1044:16
index 0 is out of range for type 'clk_hw *[*]'
CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.18.0-rc5+ #1 PREEMPT(lazy)
Hardware name: Unknown Unknown Product/Unknown Product, BIOS 2022.10spacemit 10/01/2022
Call Trace:
[<ffffffff8002b628>] dump_backtrace+0x28/0x38
[<ffffffff800027d2>] show_stack+0x3a/0x50
[<ffffffff800220c2>] dump_stack_lvl+0x5a/0x80
[<ffffffff80022100>] dump_stack+0x18/0x20
[<ffffffff800164b8>] ubsan_epilogue+0x10/0x48
[<ffffffff8099034e>] __ubsan_handle_out_of_bounds+0xa6/0xa8
[<ffffffff80acbfa6>] k1_ccu_probe+0x37e/0x420
[<ffffffff80b79e6e>] platform_probe+0x56/0x98
[<ffffffff80b76a7e>] really_probe+0x9e/0x350
[<ffffffff80b76db0>] __driver_probe_device+0x80/0x138
[<ffffffff80b76f52>] driver_probe_device+0x3a/0xd0
[<ffffffff80b771c4>] __driver_attach+0xac/0x1b8
[<ffffffff80b742fc>] bus_for_each_dev+0x6c/0xc8
[<ffffffff80b76296>] driver_attach+0x26/0x38
[<ffffffff80b759ae>] bus_add_driver+0x13e/0x268
[<ffffffff80b7836a>] driver_register+0x52/0x100
[<ffffffff80b79a78>] __platform_driver_register+0x28/0x38
[<ffffffff814585da>] k1_ccu_driver_init+0x22/0x38
[<ffffffff80023a8a>] do_one_initcall+0x62/0x2a0
[<ffffffff81401c60>] do_initcalls+0x170/0x1a8
[<ffffffff81401e7a>] kernel_init_freeable+0x16a/0x1e0
[<ffffffff811f7534>] kernel_init+0x2c/0x180
[<ffffffff80025f56>] ret_from_fork_kernel+0x16/0x1d8
[<ffffffff81205336>] ret_from_fork_kernel_asm+0x16/0x18
---[ end trace ]---

This is bogus and is simply a result of KASAN consulting the `.num` member
of the struct for bounds information (as it should due to `__counted_by`)
and finding 0 set by kzalloc because it has not been initialized before
the loop that fills in the array. The easy fix is to just move the line
that sets `num` to before the loop that fills the array so that KASAN has
the information it needs to accurately conclude that the access is valid.


Fixes: 1b72c59db0add ("clk: spacemit: Add clock support for SpacemiT K1 SoC")
Tested-by: Yanko Kaneti <yaneti@...lera.com>

Signed-off-by: Charles Mirabile <cmirabil@...hat.com>
---
 drivers/clk/spacemit/ccu-k1.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/clk/spacemit/ccu-k1.c b/drivers/clk/spacemit/ccu-k1.c
index f5a9fe6ba1859..4761bc1e3b6e6 100644
--- a/drivers/clk/spacemit/ccu-k1.c
+++ b/drivers/clk/spacemit/ccu-k1.c
@@ -1018,6 +1018,8 @@ static int spacemit_ccu_register(struct device *dev,
 	if (!clk_data)
 		return -ENOMEM;
 
+	clk_data->num = data->num;
+
 	for (i = 0; i < data->num; i++) {
 		struct clk_hw *hw = data->hws[i];
 		struct ccu_common *common;
@@ -1044,8 +1046,6 @@ static int spacemit_ccu_register(struct device *dev,
 		clk_data->hws[i] = hw;
 	}
 
-	clk_data->num = data->num;
-
 	ret = devm_of_clk_add_hw_provider(dev, of_clk_hw_onecell_get, clk_data);
 	if (ret)
 		dev_err(dev, "failed to add clock hardware provider (%d)\n", ret);

base-commit: 6a23ae0a96a600d1d12557add110e0bb6e32730c
-- 
2.51.1