linux-hardening - [PATCH v2 61/63] powerpc: Split memset() to avoid multi-field overflow

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Message-Id: <20210818060533.3569517-62-keescook@chromium.org>
Date:   Tue, 17 Aug 2021 23:05:31 -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>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linux-staging@...ts.linux.dev,
        linux-block@...r.kernel.org, linux-kbuild@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        linux-hardening@...r.kernel.org
Subject: [PATCH v2 61/63] 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..59ce431da7ef 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, 3);
 		break;
 	case SMU_I2C_TRANSFER_COMBINED:
 		cmd->info.devaddr &= 0xfe;
-- 
2.30.2