diff mbox series

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

Message ID 20210818060533.3569517-62-keescook@chromium.org (mailing list archive)
State Not Applicable
Delegated to: Netdev Maintainers
Headers show
Series Introduce strict memcpy() bounds checking | expand

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Commit Message

Kees Cook Aug. 18, 2021, 6:05 a.m. UTC 
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(-)

Comments

Christophe Leroy Aug. 18, 2021, 6:42 a.m. UTC | #1 
Le 18/08/2021 à 08:05, Kees Cook a écrit :
> 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);

subaddr[] is a table, should the & be avoided ?
And while at it, why not use sizeof(subaddr) instead of 3 ?


>   		break;
>   	case SMU_I2C_TRANSFER_COMBINED:
>   		cmd->info.devaddr &= 0xfe;
>
Kees Cook Aug. 18, 2021, 10:30 p.m. UTC | #2 
On Wed, Aug 18, 2021 at 08:42:18AM +0200, Christophe Leroy wrote:
> 
> 
> Le 18/08/2021 à 08:05, Kees Cook a écrit :
> > 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);
> 
> subaddr[] is a table, should the & be avoided ?

It results in the same thing, but it's better form to not have the &; I
will fix this.

> And while at it, why not use sizeof(subaddr) instead of 3 ?

Agreed. :)

Thanks!
diff mbox series

Patch

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;