linux-kernel - [PATCH for-next 02/25] powerpc: Split memset() to avoid multi-field overflow

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Message-Id: <20210822075122.864511-3-keescook@chromium.org>
Date:   Sun, 22 Aug 2021 00:50:59 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Qinglang Miao <miaoqinglang@...wei.com>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Hulk Robot <hulkci@...wei.com>,
        Wang Wensheng <wangwensheng4@...wei.com>,
        linuxppc-dev@...ts.ozlabs.org,
        Michael Ellerman <mpe@...erman.id.au>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Daniel Micay <danielmicay@...il.com>,
        Francis Laniel <laniel_francis@...vacyrequired.com>,
        Bart Van Assche <bvanassche@....org>,
        David Gow <davidgow@...gle.com>, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com, linux-hardening@...r.kernel.org
Subject: [PATCH for-next 02/25] powerpc: Split memset() to avoid multi-field overflow

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Instead of writing across a field boundary with memset(), move the call
to just the array, and an explicit zeroing of the prior field.

Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Qinglang Miao <miaoqinglang@...wei.com>
Cc: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Hulk Robot <hulkci@...wei.com>
Cc: Wang Wensheng <wangwensheng4@...wei.com>
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Kees Cook <keescook@...omium.org>
Reviewed-by: Michael Ellerman <mpe@...erman.id.au>
Link: https://lore.kernel.org/lkml/87czqsnmw9.fsf@mpe.ellerman.id.au
---
 drivers/macintosh/smu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/macintosh/smu.c b/drivers/macintosh/smu.c
index 94fb63a7b357..3e2b25ea58a3 100644
--- a/drivers/macintosh/smu.c
+++ b/drivers/macintosh/smu.c
@@ -848,7 +848,8 @@ int smu_queue_i2c(struct smu_i2c_cmd *cmd)
 	cmd->read = cmd->info.devaddr & 0x01;
 	switch(cmd->info.type) {
 	case SMU_I2C_TRANSFER_SIMPLE:
-		memset(&cmd->info.sublen, 0, 4);
+		cmd->info.sublen = 0;
+		memset(cmd->info.subaddr, 0, sizeof(cmd->info.subaddr));
 		break;
 	case SMU_I2C_TRANSFER_COMBINED:
 		cmd->info.devaddr &= 0xfe;
-- 
2.30.2