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R. Silva" To: Dinh Nguyen , Michael Turquette , Stephen Boyd Cc: Kees Cook , linux-kernel@vger.kernel.org, "Gustavo A. R. Silva" , linux-hardening@vger.kernel.org Subject: [PATCH v2 1/2][next] clk: socfpga: Fix undefined behavior bug in struct stratix10_clock_data Message-ID: References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Spam-Status: No, score=-1.2 required=5.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on morse.vger.email Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (morse.vger.email [0.0.0.0]); Mon, 16 Oct 2023 15:07:42 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1779951536346861951 X-GMAIL-MSGID: 1779951536346861951 `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 stratix10_clock_data`, in this case `void __iomem *base;` at run-time: drivers/clk/socfpga/stratix10-clk.h: 9 struct stratix10_clock_data { 10 struct clk_hw_onecell_data clk_data; 11 void __iomem *base; 12 }; There are currently three different places where memory is allocated for `struct stratix10_clock_data`, including the flex-array `hws` in `struct clk_hw_onecell_data`: drivers/clk/socfpga/clk-agilex.c: 469 clk_data = devm_kzalloc(dev, struct_size(clk_data, clk_data.hws, 470 num_clks), GFP_KERNEL); drivers/clk/socfpga/clk-agilex.c: 509 clk_data = devm_kzalloc(dev, struct_size(clk_data, clk_data.hws, 510 num_clks), GFP_KERNEL); drivers/clk/socfpga/clk-s10.c: 400 clk_data = devm_kzalloc(dev, struct_size(clk_data, clk_data.hws, 401 num_clks), GFP_KERNEL); I'll use just one of them to describe the issue. See below. Notice that a total of 440 bytes are allocated for flexible-array member `hws` at line 469: include/dt-bindings/clock/agilex-clock.h: 70 #define AGILEX_NUM_CLKS 55 drivers/clk/socfpga/clk-agilex.c: 459 struct stratix10_clock_data *clk_data; 460 void __iomem *base; ... 466 467 num_clks = AGILEX_NUM_CLKS; 468 469 clk_data = devm_kzalloc(dev, struct_size(clk_data, clk_data.hws, 470 num_clks), GFP_KERNEL); `struct_size(clk_data, clk_data.hws, num_clks)` above translates to sizeof(struct stratix10_clock_data) + sizeof(struct clk_hw *) * 55 == 16 + 8 * 55 == 16 + 440 ^^^ | allocated bytes for flex-array `hws` 474 for (i = 0; i < num_clks; i++) 475 clk_data->clk_data.hws[i] = ERR_PTR(-ENOENT); 476 477 clk_data->base = base; and then some data is written into both `hws` and `base` objects. Fix this by placing the declaration of object `clk_data` at the end of `struct stratix10_clock_data`. Also, add a comment to make it clear that this object must always be last in the structure. -Wflex-array-member-not-at-end is coming in GCC-14, and we are getting ready to enable it globally. Fixes: ba7e258425ac ("clk: socfpga: Convert to s10/agilex/n5x to use clk_hw") Cc: stable@vger.kernel.org Reviewed-by: Kees Cook Signed-off-by: Gustavo A. R. Silva --- Changes in v2: - Mention -Wflex-array-member-not-at-end in the changelog text. v1: - Link: https://lore.kernel.org/linux-hardening/5dd8483177dc8cd91d021170b6717f2e570bab03.1697059539.git.gustavoars@kernel.org/ drivers/clk/socfpga/stratix10-clk.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/clk/socfpga/stratix10-clk.h b/drivers/clk/socfpga/stratix10-clk.h index 75234e0783e1..83fe4eb3133c 100644 --- a/drivers/clk/socfpga/stratix10-clk.h +++ b/drivers/clk/socfpga/stratix10-clk.h @@ -7,8 +7,10 @@ #define __STRATIX10_CLK_H struct stratix10_clock_data { - struct clk_hw_onecell_data clk_data; void __iomem *base; + + /* Must be last */ + struct clk_hw_onecell_data clk_data; }; struct stratix10_pll_clock {