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Message-ID: <0a59a721d54b557076cc94eabeb694d463773204.1697076650.git.gustavoars@kernel.org>
Date: Wed, 11 Oct 2023 20:17:36 -0600
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Michael Turquette <mturquette@...libre.com>,
Stephen Boyd <sboyd@...nel.org>,
Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@...hiba.co.jp>
Cc: Kees Cook <keescook@...omium.org>, linux-clk@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
"Gustavo A. R. Silva" <gustavoars@...nel.org>,
linux-hardening@...r.kernel.org
Subject: [PATCH 1/2][next] clk: visconti: Fix undefined behavior bug in
struct visconti_pll_provider
`struct clk_hw_onecell_data` is a flexible structure, which means that
it contains flexible-array member at the bottom, in this case array
`hws`:
include/linux/clk-provider.h:
1380 struct clk_hw_onecell_data {
1381 unsigned int num;
1382 struct clk_hw *hws[] __counted_by(num);
1383 };
This could potentially lead to an overwrite of the objects following
`clk_data` in `struct visconti_pll_provider`, in this case
`struct device_node *node;`, at run-time:
drivers/clk/visconti/pll.h:
16 struct visconti_pll_provider {
17 void __iomem *reg_base;
18 struct clk_hw_onecell_data clk_data;
19 struct device_node *node;
20 };
Notice that a total of 56 bytes are allocated for flexible-array `hws`
at line 328. See below:
include/dt-bindings/clock/toshiba,tmpv770x.h:
14 #define TMPV770X_NR_PLL 7
drivers/clk/visconti/pll-tmpv770x.c:
69 ctx = visconti_init_pll(np, reg_base, TMPV770X_NR_PLL);
drivers/clk/visconti/pll.c:
321 struct visconti_pll_provider * __init visconti_init_pll(struct device_node *np,
322 void __iomem *base,
323 unsigned long nr_plls)
324 {
325 struct visconti_pll_provider *ctx;
...
328 ctx = kzalloc(struct_size(ctx, clk_data.hws, nr_plls), GFP_KERNEL);
`struct_size(ctx, clk_data.hws, nr_plls)` above translates to
sizeof(struct visconti_pll_provider) + sizeof(struct clk_hw *) * 7 ==
24 + 8 * 7 == 24 + 56
^^^^
|
allocated bytes for flex array `hws`
$ pahole -C visconti_pll_provider drivers/clk/visconti/pll.o
struct visconti_pll_provider {
void * reg_base; /* 0 8 */
struct clk_hw_onecell_data clk_data; /* 8 8 */
struct device_node * node; /* 16 8 */
/* size: 24, cachelines: 1, members: 3 */
/* last cacheline: 24 bytes */
};
And then, after the allocation, some data is written into all members
of `struct visconti_pll_provider`:
332 for (i = 0; i < nr_plls; ++i)
333 ctx->clk_data.hws[i] = ERR_PTR(-ENOENT);
334
335 ctx->node = np;
336 ctx->reg_base = base;
337 ctx->clk_data.num = nr_plls;
Fix all these by placing the declaration of object `clk_data` at the
end of `struct visconti_pll_provider`. Also, add a comment to make it
clear that this object must always be last in the structure, and
prevent this bug from being introduced again in the future.
Fixes: b4cbe606dc36 ("clk: visconti: Add support common clock driver and reset driver")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
drivers/clk/visconti/pll.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/clk/visconti/pll.h b/drivers/clk/visconti/pll.h
index 01d07f1bf01b..c4bd40676da4 100644
--- a/drivers/clk/visconti/pll.h
+++ b/drivers/clk/visconti/pll.h
@@ -15,8 +15,10 @@
struct visconti_pll_provider {
void __iomem *reg_base;
- struct clk_hw_onecell_data clk_data;
struct device_node *node;
+
+ /* Must be last */
+ struct clk_hw_onecell_data clk_data;
};
#define VISCONTI_PLL_RATE(_rate, _dacen, _dsmen, \
--
2.34.1
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