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

Kees Cook
2021-08-18T06:15:19Z

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