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SubjectRe: [PATCH] exec: Copy oldsighand->action under spin-lock
On Mon, Jun 07, 2021 at 03:54:27PM +0200, Bernd Edlinger wrote:
> unshare_sighand should only access oldsighand->action
> while holding oldsighand->siglock, to make sure that
> newsighand->action is in a consistent state.
>
> Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
> ---
> fs/exec.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index d8af85f..8344fba 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -1193,11 +1193,11 @@ static int unshare_sighand(struct task_struct *me)
> return -ENOMEM;
>
> refcount_set(&newsighand->count, 1);
> - memcpy(newsighand->action, oldsighand->action,
> - sizeof(newsighand->action));
>
> write_lock_irq(&tasklist_lock);
> spin_lock(&oldsighand->siglock);
> + memcpy(newsighand->action, oldsighand->action,
> + sizeof(newsighand->action));
> rcu_assign_pointer(me->sighand, newsighand);
> spin_unlock(&oldsighand->siglock);
> write_unlock_irq(&tasklist_lock);

Oh, yeah, that's a nice catch.

Reviewed-by: Kees Cook <keescook@chromium.org>

--
Kees Cook

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