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

[Kees Cook]

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 at kernel.crashing.org>
Cc: Qinglang Miao <miaoqinglang at huawei.com>
Cc: "Gustavo A. R. Silva" <gustavoars at kernel.org>
Cc: Hulk Robot <hulkci at huawei.com>
Cc: Wang Wensheng <wangwensheng4 at huawei.com>
Cc: linuxppc-dev at lists.ozlabs.org
Signed-off-by: Kees Cook <keescook at chromium.org>
Reviewed-by: Michael Ellerman <mpe at ellerman.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