@@ -65,6 +65,16 @@ struct ww_acquire_ctx {
#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
+ /**
+ * @first_lock_dep_map: fake lockdep_map for first locked ww_mutex.
+ *
+ * lockdep requires the lockdep_map for the first locked ww_mutex
+ * in a ww transaction to remain in memory until all ww_mutexes of
+ * the transaction have been unlocked. Ensure this by keeping a
+ * fake locked ww_mutex lockdep map between ww_acquire_init() and
+ * ww_acquire_fini().
+ */
+ struct lockdep_map first_lock_dep_map;
#endif
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
unsigned int deadlock_inject_interval;
@@ -146,7 +156,10 @@ static inline void ww_acquire_init(struct ww_acquire_ctx *ctx,
debug_check_no_locks_freed((void *)ctx, sizeof(*ctx));
lockdep_init_map(&ctx->dep_map, ww_class->acquire_name,
&ww_class->acquire_key, 0);
+ lockdep_init_map(&ctx->first_lock_dep_map, ww_class->mutex_name,
+ &ww_class->mutex_key, 0);
mutex_acquire(&ctx->dep_map, 0, 0, _RET_IP_);
+ mutex_acquire_nest(&ctx->first_lock_dep_map, 0, 0, &ctx->dep_map, _RET_IP_);
#endif
#ifdef CONFIG_DEBUG_WW_MUTEX_SLOWPATH
ctx->deadlock_inject_interval = 1;
@@ -185,6 +198,7 @@ static inline void ww_acquire_done(struct ww_acquire_ctx *ctx)
static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
{
#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ mutex_release(&ctx->first_lock_dep_map, _THIS_IP_);
mutex_release(&ctx->dep_map, _THIS_IP_);
#endif
#ifdef DEBUG_WW_MUTEXES
When using mutex_acquire_nest() with a nest_lock, lockdep refcounts the number of acquired lockdep_maps of mutexes of the same class, and also keeps a pointer to the first acquired lockdep_map of a class. That pointer is then used for various comparison-, printing- and checking purposes, but there is no mechanism to actively ensure that lockdep_map stays in memory. Instead, a warning is printed if the lockdep_map is freed and there are still held locks of the same lock class, even if the lockdep_map itself has been released. In the context of WW/WD transactions that means that if a user unlocks and frees a ww_mutex from within an ongoing ww transaction, and that mutex happens to be the first ww_mutex grabbed in the transaction, such a warning is printed and there might be a risk of a UAF. Note that this is only problem when lockdep is enabled and affects only dereferences of struct lockdep_map. Adjust to this by adding a fake lockdep_map to the acquired context and make sure it is the first acquired lockdep map of the associated ww_mutex class. Then hold it for the duration of the WW/WD transaction. Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Will Deacon <will@kernel.org> Cc: Waiman Long <longman@redhat.com> Cc: Boqun Feng <boqun.feng@gmail.com> Cc: Daniel Vetter <daniel.vetter@intel.com> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> Cc: Christian König <christian.koenig@amd.com> Cc: intel-xe@lists.freedesktop.org Cc: intel-gfx@lists.freedesktop.org Cc: dri-devel@lists.freedestkop.org Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com> --- include/linux/ww_mutex.h | 14 ++++++++++++++ 1 file changed, 14 insertions(+)