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SubjectRe: [PATCH 1/2] security/apparmor: Replace homebrew use of write_can_lock with lockdep
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On 10/03/2017 07:32 AM, Will Deacon wrote:
> The lockdep subsystem provides a robust way to assert that a lock is
> held, so use that instead of write_can_lock, which can give incorrect
> results for qrwlocks.
>
> Cc: John Johansen <john.johansen@canonical.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Will Deacon <will.deacon@arm.com>

oh nice,

Acked-by: John Johansen <john.johansen@canonical.com>



> ---
> security/apparmor/include/lib.h | 11 -----------
> security/apparmor/label.c | 8 ++++----
> 2 files changed, 4 insertions(+), 15 deletions(-)
>
> diff --git a/security/apparmor/include/lib.h b/security/apparmor/include/lib.h
> index 436b3a722357..f546707a2bbb 100644
> --- a/security/apparmor/include/lib.h
> +++ b/security/apparmor/include/lib.h
> @@ -19,17 +19,6 @@
>
> #include "match.h"
>
> -/* Provide our own test for whether a write lock is held for asserts
> - * this is because on none SMP systems write_can_lock will always
> - * resolve to true, which is what you want for code making decisions
> - * based on it, but wrong for asserts checking that the lock is held
> - */
> -#ifdef CONFIG_SMP
> -#define write_is_locked(X) !write_can_lock(X)
> -#else
> -#define write_is_locked(X) (1)
> -#endif /* CONFIG_SMP */
> -
> /*
> * DEBUG remains global (no per profile flag) since it is mostly used in sysctl
> * which is not related to profile accesses.
> diff --git a/security/apparmor/label.c b/security/apparmor/label.c
> index c5b99b954580..ad28e03a6f30 100644
> --- a/security/apparmor/label.c
> +++ b/security/apparmor/label.c
> @@ -80,7 +80,7 @@ void __aa_proxy_redirect(struct aa_label *orig, struct aa_label *new)
>
> AA_BUG(!orig);
> AA_BUG(!new);
> - AA_BUG(!write_is_locked(&labels_set(orig)->lock));
> + lockdep_assert_held_exclusive(&labels_set(orig)->lock);
>
> tmp = rcu_dereference_protected(orig->proxy->label,
> &labels_ns(orig)->lock);
> @@ -571,7 +571,7 @@ static bool __label_remove(struct aa_label *label, struct aa_label *new)
>
> AA_BUG(!ls);
> AA_BUG(!label);
> - AA_BUG(!write_is_locked(&ls->lock));
> + lockdep_assert_held_exclusive(&ls->lock);
>
> if (new)
> __aa_proxy_redirect(label, new);
> @@ -608,7 +608,7 @@ static bool __label_replace(struct aa_label *old, struct aa_label *new)
> AA_BUG(!ls);
> AA_BUG(!old);
> AA_BUG(!new);
> - AA_BUG(!write_is_locked(&ls->lock));
> + lockdep_assert_held_exclusive(&ls->lock);
> AA_BUG(new->flags & FLAG_IN_TREE);
>
> if (!label_is_stale(old))
> @@ -645,7 +645,7 @@ static struct aa_label *__label_insert(struct aa_labelset *ls,
> AA_BUG(!ls);
> AA_BUG(!label);
> AA_BUG(labels_set(label) != ls);
> - AA_BUG(!write_is_locked(&ls->lock));
> + lockdep_assert_held_exclusive(&ls->lock);
> AA_BUG(label->flags & FLAG_IN_TREE);
>
> /* Figure out where to put new node */
>

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