[PATCH 02/10] drbd: Remove uninitialized_var() usage

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Kees Cook

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Jun 3, 2020, 7:32:16 PM6/3/20
to linux-...@vger.kernel.org, Kees Cook, Linus Torvalds, Miguel Ojeda, Alexander Potapenko, Joe Perches, Andy Whitcroft, x...@kernel.org, drbd...@lists.linbit.com, linux...@vger.kernel.org, b43...@lists.infradead.org, net...@vger.kernel.org, linux-w...@vger.kernel.org, linu...@vger.kernel.org, linu...@vger.kernel.org, linu...@vger.kernel.org, linu...@kvack.org, clang-bu...@googlegroups.com
Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings (e.g.
"unused variable"). If the compiler thinks it is uninitialized, either
simply initialize the variable or make compiler changes. As a precursor
to removing[2] this[3] macro[4], just initialize this variable to NULL.

[1] https://lore.kernel.org/lkml/20200603174714....@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK...@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpz...@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN...@mail.gmail.com/

Signed-off-by: Kees Cook <kees...@chromium.org>
---
drivers/block/drbd/drbd_state.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index eeaa3b49b264..0067d328f0b5 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -1604,7 +1604,7 @@ static void broadcast_state_change(struct drbd_state_change *state_change)
unsigned int n_device, n_connection, n_peer_device, n_peer_devices;
void (*last_func)(struct sk_buff *, unsigned int, void *,
enum drbd_notification_type) = NULL;
- void *uninitialized_var(last_arg);
+ void *last_arg = NULL;

#define HAS_CHANGED(state) ((state)[OLD] != (state)[NEW])
#define FINAL_STATE_CHANGE(type) \
--
2.25.1

Nick Desaulniers

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Jun 4, 2020, 3:56:25 PM6/4/20
to Kees Cook, LKML, Linus Torvalds, Miguel Ojeda, Alexander Potapenko, Joe Perches, Andy Whitcroft, maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT), drbd...@lists.linbit.com, linux...@vger.kernel.org, b43...@lists.infradead.org, Network Development, linux-wireless, linu...@vger.kernel.org, linu...@vger.kernel.org, linu...@vger.kernel.org, Linux Memory Management List, clang-built-linux
On Wed, Jun 3, 2020 at 4:32 PM Kees Cook <kees...@chromium.org> wrote:
>
> Using uninitialized_var() is dangerous as it papers over real bugs[1]
> (or can in the future), and suppresses unrelated compiler warnings (e.g.
> "unused variable"). If the compiler thinks it is uninitialized, either
> simply initialize the variable or make compiler changes. As a precursor
> to removing[2] this[3] macro[4], just initialize this variable to NULL.
>
> [1] https://lore.kernel.org/lkml/20200603174714....@google.com/
> [2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK...@mail.gmail.com/
> [3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpz...@mail.gmail.com/
> [4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN...@mail.gmail.com/
>
> Signed-off-by: Kees Cook <kees...@chromium.org>

Reviewed-by: Nick Desaulniers <ndesau...@google.com>
Fixes: a29728463b25 ("drbd: Backport the "events2" command")

> ---
> drivers/block/drbd/drbd_state.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
> index eeaa3b49b264..0067d328f0b5 100644
> --- a/drivers/block/drbd/drbd_state.c
> +++ b/drivers/block/drbd/drbd_state.c
> @@ -1604,7 +1604,7 @@ static void broadcast_state_change(struct drbd_state_change *state_change)
> unsigned int n_device, n_connection, n_peer_device, n_peer_devices;
> void (*last_func)(struct sk_buff *, unsigned int, void *,
> enum drbd_notification_type) = NULL;
> - void *uninitialized_var(last_arg);
> + void *last_arg = NULL;
>
> #define HAS_CHANGED(state) ((state)[OLD] != (state)[NEW])
> #define FINAL_STATE_CHANGE(type) \
> --
> 2.25.1
>
> --
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--
Thanks,
~Nick Desaulniers
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