On Mon, Mar 2, 2020 at 5:04 AM <glider@xxxxxxxxxx> wrote:
>
> With CONFIG_INIT_STACK_ALL enabled, the local __wq_entry is initialized
> twice. Because Clang is currently unable to optimize the automatic
> initialization away (init_wait_entry() is defined in another translation
> unit), remove it with the __no_initialize annotation.
>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
>
> ---
> v2:
> - changed __do_not_initialize to __no_initialize as requested by Kees
> Cook
> ---
> drivers/android/binder.c | 4 ++--
> include/linux/wait.h | 3 ++-
> 2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index a59871532ff6b..66984e7c33094 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -4827,7 +4827,7 @@ static int binder_ioctl_write_read(struct file *filp,
> struct binder_proc *proc = filp->private_data;
> unsigned int size = _IOC_SIZE(cmd);
> void __user *ubuf = (void __user *)arg;
> - struct binder_write_read bwr __no_initialize;
> + struct binder_write_read bwr;
How did __no_initialize get set so that it can be removed here? Should
the addition of __no_initilize be removed earlier in the series (tip
doesn't have the __no_initialize).
>
> if (size != sizeof(struct binder_write_read)) {
> ret = -EINVAL;
> @@ -5026,7 +5026,7 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> goto err;
> break;
> case BINDER_SET_MAX_THREADS: {
> - int max_threads;
> + int max_threads __no_initialize;
Is this really needed? A single integer in a rarely called ioctl()
being initialized twice doesn't warrant this optimization.
>
> if (copy_from_user(&max_threads, ubuf,
> sizeof(max_threads))) {
> diff --git a/include/linux/wait.h b/include/linux/wait.h
> index 3283c8d021377..b52a9bb2c7727 100644
> --- a/include/linux/wait.h
> +++ b/include/linux/wait.h
> @@ -262,7 +262,8 @@ extern void init_wait_entry(struct wait_queue_entry *wq_entry, int flags);
> #define ___wait_event(wq_head, condition, state, exclusive, ret, cmd) \
> ({ \
> __label__ __out; \
> - struct wait_queue_entry __wq_entry; \
> + /* Unconditionally initialized by init_wait_entry(). */ \
> + struct wait_queue_entry __wq_entry __no_initialize; \
> long __ret = ret; /* explicit shadow */ \
> \
> init_wait_entry(&__wq_entry, exclusive ? WQ_FLAG_EXCLUSIVE : 0); \
> --
> 2.25.0.265.gbab2e86ba0-goog
>
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