Merge changes Ibdc46d20,Icbcc37c2,I8c5aa13b,I10a0c2aa,Iebc150f6, ... into android-chromeos-dragon-3.18-nyc

* changes:
  ecryptfs: don't allow mmap when the lower fs doesn't support it
  Revert "ecryptfs: forbid opening files without mmap handler"
  UPSTREAM: arm64: make sys_call_table const
  ion: blacklist %p kptr_restrict
  binder: blacklist %p kptr_restrict
  BACKPORT: android: binder: fix binder mmap failures
  BACKPORT: perf: Fix event->ctx locking
  UPSTREAM: perf: Fix events installation during moving group
  perf: protect group_leader from races that cause ctx double-free
  UPSTREAM: staging/android/ion : fix a race condition in the ion driver
  drm/tegra: Check args->num_syncpts limit

8 files changed, 322 insertions, 98 deletions

diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
index 3fa98ff14f0e..df20b7918854 100644
--- a/arch/arm64/kernel/sys.c
+++ b/arch/arm64/kernel/sys.c
@@ -50,7 +50,7 @@ asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
  * The sys_call_table array must be 4K aligned to be accessible from
  * kernel/entry.S.
  */
-void *sys_call_table[__NR_syscalls] __aligned(4096) = {
+void * const sys_call_table[__NR_syscalls] __aligned(4096) = {
 	[0 ... __NR_syscalls - 1] = sys_ni_syscall,
 #include <asm/unistd.h>
 };
diff --git a/drivers/gpu/drm/tegra/drm.c b/drivers/gpu/drm/tegra/drm.c
index 8ba928c96d7b..0991569cf7fb 100644
--- a/drivers/gpu/drm/tegra/drm.c
+++ b/drivers/gpu/drm/tegra/drm.c
@@ -468,9 +468,10 @@ int tegra_drm_submit(struct tegra_drm_context *context,
 
 	/*
 	 * Doesn't make sense to submit a job without synchronizing on at least
-	 * one syncpt.
+	 * one syncpt.  Also check client num_syncpts limit.
 	 */
-	if (!args->num_syncpts)
+	if (!args->num_syncpts ||
+	    (args->num_syncpts > context->client->base.num_syncpts))
 		return -EINVAL;
 
 	job = host1x_job_alloc(context->channel, args->num_cmdbufs,
diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c
index ed770e420824..c7415b4b4446 100644
--- a/drivers/staging/android/binder.c
+++ b/drivers/staging/android/binder.c
@@ -536,7 +536,7 @@ static void binder_insert_free_buffer(struct binder_proc *proc,
 	new_buffer_size = binder_buffer_size(proc, new_buffer);
 
 	binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-		     "%d: add free buffer, size %zd, at %p\n",
+		     "%d: add free buffer, size %zd, at %pK\n",
 		      proc->pid, new_buffer_size, new_buffer);
 
 	while (*p) {
@@ -610,12 +610,11 @@ static int binder_update_page_range(struct binder_proc *proc, int allocate,
 {
 	void *page_addr;
 	unsigned long user_page_addr;
-	struct vm_struct tmp_area;
 	struct page **page;
 	struct mm_struct *mm;
 
 	binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-		     "%d: %s pages %p-%p\n", proc->pid,
+		     "%d: %s pages %pK-%pK\n", proc->pid,
 		     allocate ? "allocate" : "free", start, end);
 
 	if (end <= start)
@@ -649,7 +648,6 @@ static int binder_update_page_range(struct binder_proc *proc, int allocate,
 		goto err_no_vma;
 	}
 
-	memset(&tmp_area, 0, sizeof(tmp_area));
 	for (page_addr = start; page_addr < end; page_addr += PAGE_SIZE) {
 		int ret;
 
@@ -658,15 +656,16 @@ static int binder_update_page_range(struct binder_proc *proc, int allocate,
 		BUG_ON(*page);
 		*page = alloc_page(GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO);
 		if (*page == NULL) {
-			pr_err("%d: binder_alloc_buf failed for page at %p\n",
+			pr_err("%d: binder_alloc_buf failed for page at %pK\n",
 				proc->pid, page_addr);
 			goto err_alloc_page_failed;
 		}
-		tmp_area.addr = page_addr;
-		tmp_area.size = PAGE_SIZE + PAGE_SIZE /* guard page? */;
-		ret = map_vm_area(&tmp_area, PAGE_KERNEL, page);
-		if (ret) {
-			pr_err("%d: binder_alloc_buf failed to map page at %p in kernel\n",
+		ret = map_kernel_range_noflush((unsigned long)page_addr,
+					PAGE_SIZE, PAGE_KERNEL, page);
+		flush_cache_vmap((unsigned long)page_addr,
+				(unsigned long)page_addr + PAGE_SIZE);
+		if (ret != 1) {
+			pr_err("%d: binder_alloc_buf failed to map page at %pK in kernel\n",
 			       proc->pid, page_addr);
 			goto err_map_kernel_failed;
 		}
@@ -776,7 +775,7 @@ static struct binder_buffer *binder_alloc_buf(struct binder_proc *proc,
 	}
 
 	binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-		     "%d: binder_alloc_buf size %zd got buffer %p size %zd\n",
+		     "%d: binder_alloc_buf size %zd got buffer %pK size %zd\n",
 		      proc->pid, size, buffer, buffer_size);
 
 	has_page_addr =
@@ -806,7 +805,7 @@ static struct binder_buffer *binder_alloc_buf(struct binder_proc *proc,
 		binder_insert_free_buffer(proc, new_buffer);
 	}
 	binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-		     "%d: binder_alloc_buf size %zd got %p\n",
+		     "%d: binder_alloc_buf size %zd got %pK\n",
 		      proc->pid, size, buffer);
 	buffer->data_size = data_size;
 	buffer->offsets_size = offsets_size;
@@ -846,7 +845,7 @@ static void binder_delete_free_buffer(struct binder_proc *proc,
 		if (buffer_end_page(prev) == buffer_end_page(buffer))
 			free_page_end = 0;
 		binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-			     "%d: merge free, buffer %p share page with %p\n",
+			     "%d: merge free, buffer %pK share page with %pK\n",
 			      proc->pid, buffer, prev);
 	}
 
@@ -859,14 +858,14 @@ static void binder_delete_free_buffer(struct binder_proc *proc,
 			    buffer_start_page(buffer))
 				free_page_start = 0;
 			binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-				     "%d: merge free, buffer %p share page with %p\n",
+				     "%d: merge free, buffer %pK share page with %pK\n",
 				      proc->pid, buffer, prev);
 		}
 	}
 	list_del(&buffer->entry);
 	if (free_page_start || free_page_end) {
 		binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-			     "%d: merge free, buffer %p do not share page%s%s with %p or %p\n",
+			     "%d: merge free, buffer %pK do not share page%s%s with %pK or %pK\n",
 			     proc->pid, buffer, free_page_start ? "" : " end",
 			     free_page_end ? "" : " start", prev, next);
 		binder_update_page_range(proc, 0, free_page_start ?
@@ -887,7 +886,7 @@ static void binder_free_buf(struct binder_proc *proc,
 		ALIGN(buffer->offsets_size, sizeof(void *));
 
 	binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-		     "%d: binder_free_buf %p size %zd buffer_size %zd\n",
+		     "%d: binder_free_buf %pK size %zd buffer_size %zd\n",
 		      proc->pid, buffer, size, buffer_size);
 
 	BUG_ON(buffer->free);
@@ -1317,7 +1316,7 @@ static void binder_transaction_buffer_release(struct binder_proc *proc,
 	int debug_id = buffer->debug_id;
 
 	binder_debug(BINDER_DEBUG_TRANSACTION,
-		     "%d buffer release %d, size %zd-%zd, failed at %p\n",
+		     "%d buffer release %d, size %zd-%zd, failed at %pK\n",
 		     proc->pid, buffer->debug_id,
 		     buffer->data_size, buffer->offsets_size, failed_at);
 
@@ -2172,7 +2171,7 @@ static int binder_thread_write(struct binder_proc *proc,
 				}
 			}
 			binder_debug(BINDER_DEBUG_DEAD_BINDER,
-				     "%d:%d BC_DEAD_BINDER_DONE %016llx found %p\n",
+				     "%d:%d BC_DEAD_BINDER_DONE %016llx found %pK\n",
 				     proc->pid, thread->pid, (u64)cookie,
 				     death);
 			if (death == NULL) {
@@ -2977,7 +2976,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
 #ifdef CONFIG_CPU_CACHE_VIPT
 	if (cache_is_vipt_aliasing()) {
 		while (CACHE_COLOUR((vma->vm_start ^ (uint32_t)proc->buffer))) {
-			pr_info("binder_mmap: %d %lx-%lx maps %p bad alignment\n", proc->pid, vma->vm_start, vma->vm_end, proc->buffer);
+			pr_info("binder_mmap: %d %lx-%lx maps %pK bad alignment\n", proc->pid, vma->vm_start, vma->vm_end, proc->buffer);
 			vma->vm_start += PAGE_SIZE;
 		}
 	}
@@ -3013,7 +3012,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
 	proc->vma = vma;
 	proc->vma_vm_mm = vma->vm_mm;
 
-	/*pr_info("binder_mmap: %d %lx-%lx maps %p\n",
+	/*pr_info("binder_mmap: %d %lx-%lx maps %pK\n",
 		 proc->pid, vma->vm_start, vma->vm_end, proc->buffer);*/
 	return 0;
 
@@ -3239,7 +3238,7 @@ static void binder_deferred_release(struct binder_proc *proc)
 
 			page_addr = proc->buffer + i * PAGE_SIZE;
 			binder_debug(BINDER_DEBUG_BUFFER_ALLOC,
-				     "%s: %d: page %d at %p not freed\n",
+				     "%s: %d: page %d at %pK not freed\n",
 				     __func__, proc->pid, i, page_addr);
 			unmap_kernel_range((unsigned long)page_addr, PAGE_SIZE);
 			__free_page(proc->pages[i]);
@@ -3324,7 +3323,7 @@ static void print_binder_transaction(struct seq_file *m, const char *prefix,
 				     struct binder_transaction *t)
 {
 	seq_printf(m,
-		   "%s %d: %p from %d:%d to %d:%d code %x flags %x pri %ld r%d",
+		   "%s %d: %pK from %d:%d to %d:%d code %x flags %x pri %ld r%d",
 		   prefix, t->debug_id, t,
 		   t->from ? t->from->proc->pid : 0,
 		   t->from ? t->from->pid : 0,
@@ -3338,7 +3337,7 @@ static void print_binder_transaction(struct seq_file *m, const char *prefix,
 	if (t->buffer->target_node)
 		seq_printf(m, " node %d",
 			   t->buffer->target_node->debug_id);
-	seq_printf(m, " size %zd:%zd data %p\n",
+	seq_printf(m, " size %zd:%zd data %pK\n",
 		   t->buffer->data_size, t->buffer->offsets_size,
 		   t->buffer->data);
 }
@@ -3346,7 +3345,7 @@ static void print_binder_transaction(struct seq_file *m, const char *prefix,
 static void print_binder_buffer(struct seq_file *m, const char *prefix,
 				struct binder_buffer *buffer)
 {
-	seq_printf(m, "%s %d: %p size %zd:%zd %s\n",
+	seq_printf(m, "%s %d: %pK size %zd:%zd %s\n",
 		   prefix, buffer->debug_id, buffer->data,
 		   buffer->data_size, buffer->offsets_size,
 		   buffer->transaction ? "active" : "delivered");
diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
index a22521df6480..06dcd41c4a50 100644
--- a/drivers/staging/android/ion/ion.c
+++ b/drivers/staging/android/ion/ion.c
@@ -420,13 +420,22 @@ static void ion_handle_get(struct ion_handle *handle)
 	kref_get(&handle->ref);
 }
 
-static int ion_handle_put(struct ion_handle *handle)
+static int ion_handle_put_nolock(struct ion_handle *handle)
+{
+	int ret;
+
+	ret = kref_put(&handle->ref, ion_handle_destroy);
+
+	return ret;
+}
+
+int ion_handle_put(struct ion_handle *handle)
 {
 	struct ion_client *client = handle->client;
 	int ret;
 
 	mutex_lock(&client->lock);
-	ret = kref_put(&handle->ref, ion_handle_destroy);
+	ret = ion_handle_put_nolock(handle);
 	mutex_unlock(&client->lock);
 
 	return ret;
@@ -450,20 +459,30 @@ static struct ion_handle *ion_handle_lookup(struct ion_client *client,
 	return ERR_PTR(-EINVAL);
 }
 
-static struct ion_handle *ion_handle_get_by_id(struct ion_client *client,
+static struct ion_handle *ion_handle_get_by_id_nolock(struct ion_client *client,
 						int id)
 {
 	struct ion_handle *handle;
 
-	mutex_lock(&client->lock);
 	handle = idr_find(&client->idr, id);
 	if (handle)
 		ion_handle_get(handle);
-	mutex_unlock(&client->lock);
 
 	return handle ? handle : ERR_PTR(-EINVAL);
 }
 
+struct ion_handle *ion_handle_get_by_id(struct ion_client *client,
+						int id)
+{
+	struct ion_handle *handle;
+
+	mutex_lock(&client->lock);
+	handle = ion_handle_get_by_id_nolock(client, id);
+	mutex_unlock(&client->lock);
+
+	return handle;
+}
+
 static bool ion_handle_validate(struct ion_client *client,
 				struct ion_handle *handle)
 {
@@ -571,22 +590,28 @@ struct ion_handle *ion_alloc(struct ion_client *client, size_t len,
 }
 EXPORT_SYMBOL(ion_alloc);
 
-void ion_free(struct ion_client *client, struct ion_handle *handle)
+static void ion_free_nolock(struct ion_client *client, struct ion_handle *handle)
 {
 	bool valid_handle;
 
 	BUG_ON(client != handle->client);
 
-	mutex_lock(&client->lock);
 	valid_handle = ion_handle_validate(client, handle);
 
 	if (!valid_handle) {
 		WARN(1, "%s: invalid handle passed to free.\n", __func__);
-		mutex_unlock(&client->lock);
 		return;
 	}
+	ion_handle_put_nolock(handle);
+}
+
+void ion_free(struct ion_client *client, struct ion_handle *handle)
+{
+	BUG_ON(client != handle->client);
+
+	mutex_lock(&client->lock);
+	ion_free_nolock(client, handle);
 	mutex_unlock(&client->lock);
-	ion_handle_put(handle);
 }
 EXPORT_SYMBOL(ion_free);
 
@@ -1167,7 +1192,7 @@ static void ion_unmap_dma_buf(struct dma_buf_attachment *attachment,
 		}
 	}
 
-	dev_warn(attachment->dev, "Not found a map(%p)\n",
+	dev_warn(attachment->dev, "Not found a map(%pK)\n",
 		 to_dma_iommu_mapping(attachment->dev));
 
 	mutex_unlock(&buffer->lock);
@@ -1258,7 +1283,7 @@ static void ion_vm_open(struct vm_area_struct *vma)
 	mutex_lock(&buffer->lock);
 	list_add(&vma_list->list, &buffer->vmas);
 	mutex_unlock(&buffer->lock);
-	pr_debug("%s: adding %p\n", __func__, vma);
+	pr_debug("%s: adding %pK\n", __func__, vma);
 }
 
 static void ion_vm_close(struct vm_area_struct *vma)
@@ -1273,7 +1298,7 @@ static void ion_vm_close(struct vm_area_struct *vma)
 			continue;
 		list_del(&vma_list->list);
 		kfree(vma_list);
-		pr_debug("%s: deleting %p\n", __func__, vma);
+		pr_debug("%s: deleting %pK\n", __func__, vma);
 		break;
 	}
 	mutex_unlock(&buffer->lock);
@@ -1395,7 +1420,7 @@ static int ion_dma_buf_set_private(struct dma_buf *dmabuf, struct device *dev,
 	imp->delete = delete;
 out:
 	mutex_unlock(&buffer->lock);
-	dev_dbg(dev, "%s() dmabuf=%p err=%d i=%d priv=%p\n",
+	dev_dbg(dev, "%s() dmabuf=%pK err=%d i=%d priv=%pK\n",
 		__func__, dmabuf, err, i, priv);
 	return err;
 }
@@ -1418,7 +1443,7 @@ static void *ion_dma_buf_get_private(struct dma_buf *dmabuf,
 		}
 	}
 	mutex_unlock(&buffer->lock);
-	dev_dbg(dev, "%s() dmabuf=%p i=%d priv=%p\n",
+	dev_dbg(dev, "%s() dmabuf=%pK i=%d priv=%pK\n",
 		__func__, dmabuf, i, priv);
 	return priv;
 }
@@ -1445,13 +1470,13 @@ static void *ion_dma_buf_vmap(struct dma_buf *dmabuf)
 {
 	void *addr = ion_dma_buf_kmap(dmabuf, 0);
 
-	pr_info("%s() %p\n", __func__, addr);
+	pr_info("%s() %pK\n", __func__, addr);
 	return addr;
 }
 
 static void ion_dma_buf_vunmap(struct dma_buf *dmabuf, void *vaddr)
 {
-	pr_info("%s() %p\n", __func__, vaddr);
+	pr_info("%s() %pK\n", __func__, vaddr);
 	ion_dma_buf_kunmap(dmabuf, 0, vaddr);
 }
 
@@ -1786,11 +1811,15 @@ static long ion_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	{
 		struct ion_handle *handle;
 
-		handle = ion_handle_get_by_id(client, data.handle.handle);
-		if (IS_ERR(handle))
+		mutex_lock(&client->lock);
+		handle = ion_handle_get_by_id_nolock(client, data.handle.handle);
+		if (IS_ERR(handle)) {
+			mutex_unlock(&client->lock);
 			return PTR_ERR(handle);
-		ion_free(client, handle);
-		ion_handle_put(handle);
+		}
+		ion_free_nolock(client, handle);
+		ion_handle_put_nolock(handle);
+		mutex_unlock(&client->lock);
 		break;
 	}
 	case ION_IOC_SHARE:
diff --git a/fs/ecryptfs/file.c b/fs/ecryptfs/file.c
index f5bce9096555..644dc16fa11a 100644
--- a/fs/ecryptfs/file.c
+++ b/fs/ecryptfs/file.c
@@ -177,6 +177,19 @@ out:
 	return rc;
 }
 
+static int ecryptfs_mmap(struct file *file, struct vm_area_struct *vma)
+{
+	struct file *lower_file = ecryptfs_file_to_lower(file);
+	/*
+	 * Don't allow mmap on top of file systems that don't support it
+	 * natively.  If FILESYSTEM_MAX_STACK_DEPTH > 2 or ecryptfs
+	 * allows recursive mounting, this will need to be extended.
+	 */
+	if (!lower_file->f_op->mmap)
+		return -ENODEV;
+	return generic_file_mmap(file, vma);
+}
+
 /**
  * ecryptfs_open
  * @inode: inode speciying file to open
@@ -360,7 +373,7 @@ const struct file_operations ecryptfs_main_fops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = ecryptfs_compat_ioctl,
 #endif
-	.mmap = generic_file_mmap,
+	.mmap = ecryptfs_mmap,
 	.open = ecryptfs_open,
 	.flush = ecryptfs_flush,
 	.release = ecryptfs_release,
diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c
index 9b661a4ccee7..f1ea610362c6 100644
--- a/fs/ecryptfs/kthread.c
+++ b/fs/ecryptfs/kthread.c
@@ -25,7 +25,6 @@
 #include <linux/slab.h>
 #include <linux/wait.h>
 #include <linux/mount.h>
-#include <linux/file.h>
 #include "ecryptfs_kernel.h"
 
 struct ecryptfs_open_req {
@@ -148,7 +147,7 @@ int ecryptfs_privileged_open(struct file **lower_file,
 	flags |= IS_RDONLY(lower_dentry->d_inode) ? O_RDONLY : O_RDWR;
 	(*lower_file) = dentry_open(&req.path, flags, cred);
 	if (!IS_ERR(*lower_file))
-		goto have_file;
+		goto out;
 	if ((flags & O_ACCMODE) == O_RDONLY) {
 		rc = PTR_ERR((*lower_file));
 		goto out;
@@ -166,16 +165,8 @@ int ecryptfs_privileged_open(struct file **lower_file,
 	mutex_unlock(&ecryptfs_kthread_ctl.mux);
 	wake_up(&ecryptfs_kthread_ctl.wait);
 	wait_for_completion(&req.done);
-	if (IS_ERR(*lower_file)) {
+	if (IS_ERR(*lower_file))
 		rc = PTR_ERR(*lower_file);
-		goto out;
-	}
-have_file:
-	if ((*lower_file)->f_op->mmap == NULL) {
-		fput(*lower_file);
-		*lower_file = NULL;
-		rc = -EMEDIUMTYPE;
-	}
 out:
 	return rc;
 }
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 948b07d0cd71..15970d1ba73f 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -337,6 +337,12 @@ struct perf_event {
 	int				nr_siblings;
 	int				group_flags;
 	struct perf_event		*group_leader;
+
+	/*
+	 * Protect the pmu, attributes and context of a group leader.
+	 * Note: does not protect the pointer to the group_leader.
+	 */
+	struct mutex			group_leader_mutex;
 	struct pmu			*pmu;
 
 	enum perf_event_active_state	state;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6ac16003c284..2cc213668cf6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -912,6 +912,77 @@ static void put_ctx(struct perf_event_context *ctx)
 }
 
 /*
+ * Because of perf_event::ctx migration in sys_perf_event_open::move_group and
+ * perf_pmu_migrate_context() we need some magic.
+ *
+ * Those places that change perf_event::ctx will hold both
+ * perf_event_ctx::mutex of the 'old' and 'new' ctx value.
+ *
+ * Lock ordering is by mutex address. There is one other site where
+ * perf_event_context::mutex nests and that is put_event(). But remember that
+ * that is a parent<->child context relation, and migration does not affect
+ * children, therefore these two orderings should not interact.
+ *
+ * The change in perf_event::ctx does not affect children (as claimed above)
+ * because the sys_perf_event_open() case will install a new event and break
+ * the ctx parent<->child relation, and perf_pmu_migrate_context() is only
+ * concerned with cpuctx and that doesn't have children.
+ *
+ * The places that change perf_event::ctx will issue:
+ *
+ *   perf_remove_from_context();
+ *   synchronize_rcu();
+ *   perf_install_in_context();
+ *
+ * to affect the change. The remove_from_context() + synchronize_rcu() should
+ * quiesce the event, after which we can install it in the new location. This
+ * means that only external vectors (perf_fops, prctl) can perturb the event
+ * while in transit. Therefore all such accessors should also acquire
+ * perf_event_context::mutex to serialize against this.
+ *
+ * However; because event->ctx can change while we're waiting to acquire
+ * ctx->mutex we must be careful and use the below perf_event_ctx_lock()
+ * function.
+ *
+ * Lock order:
+ *	task_struct::perf_event_mutex
+ *	  perf_event_context::mutex
+ *	    perf_event_context::lock
+ *	    perf_event::child_mutex;
+ *	    perf_event::mmap_mutex
+ *	    mmap_sem
+ */
+static struct perf_event_context *perf_event_ctx_lock(struct perf_event *event)
+{
+	struct perf_event_context *ctx;
+
+again:
+	rcu_read_lock();
+	ctx = ACCESS_ONCE(event->ctx);
+	if (!atomic_inc_not_zero(&ctx->refcount)) {
+		rcu_read_unlock();
+		goto again;
+	}
+	rcu_read_unlock();
+
+	mutex_lock(&ctx->mutex);
+	if (event->ctx != ctx) {
+		mutex_unlock(&ctx->mutex);
+		put_ctx(ctx);
+		goto again;
+	}
+
+	return ctx;
+}
+
+static void perf_event_ctx_unlock(struct perf_event *event,
+				  struct perf_event_context *ctx)
+{
+	mutex_unlock(&ctx->mutex);
+	put_ctx(ctx);
+}
+
+/*
  * This must be done under the ctx->lock, such as to serialize against
  * context_equiv(), therefore we cannot call put_ctx() since that might end up
  * calling scheduler related locks and ctx->lock nests inside those.
@@ -1659,7 +1730,7 @@ int __perf_event_disable(void *info)
  * is the current context on this CPU and preemption is disabled,
  * hence we can't get into perf_event_task_sched_out for this context.
  */
-void perf_event_disable(struct perf_event *event)
+static void _perf_event_disable(struct perf_event *event)
 {
 	struct perf_event_context *ctx = event->ctx;
 	struct task_struct *task = ctx->task;
@@ -1700,6 +1771,19 @@ retry:
 	}
 	raw_spin_unlock_irq(&ctx->lock);
 }
+
+/*
+ * Strictly speaking kernel users cannot create groups and therefore this
+ * interface does not need the perf_event_ctx_lock() magic.
+ */
+void perf_event_disable(struct perf_event *event)
+{
+	struct perf_event_context *ctx;
+
+	ctx = perf_event_ctx_lock(event);
+	_perf_event_disable(event);
+	perf_event_ctx_unlock(event, ctx);
+}
 EXPORT_SYMBOL_GPL(perf_event_disable);
 
 static void perf_set_shadow_time(struct perf_event *event,
@@ -2163,7 +2247,7 @@ unlock:
  * perf_event_for_each_child or perf_event_for_each as described
  * for perf_event_disable.
  */
-void perf_event_enable(struct perf_event *event)
+static void _perf_event_enable(struct perf_event *event)
 {
 	struct perf_event_context *ctx = event->ctx;
 	struct task_struct *task = ctx->task;
@@ -2219,9 +2303,21 @@ retry:
 out:
 	raw_spin_unlock_irq(&ctx->lock);
 }
+
+/*
+ * See perf_event_disable();
+ */
+void perf_event_enable(struct perf_event *event)
+{
+	struct perf_event_context *ctx;
+
+	ctx = perf_event_ctx_lock(event);
+	_perf_event_enable(event);
+	perf_event_ctx_unlock(event, ctx);
+}
 EXPORT_SYMBOL_GPL(perf_event_enable);
 
-int perf_event_refresh(struct perf_event *event, int refresh)
+static int _perf_event_refresh(struct perf_event *event, int refresh)
 {
 	/*
 	 * not supported on inherited events
@@ -2230,10 +2326,25 @@ int perf_event_refresh(struct perf_event *event, int refresh)
 		return -EINVAL;
 
 	atomic_add(refresh, &event->event_limit);
-	perf_event_enable(event);
+	_perf_event_enable(event);
 
 	return 0;
 }
+
+/*
+ * See perf_event_disable()
+ */
+int perf_event_refresh(struct perf_event *event, int refresh)
+{
+	struct perf_event_context *ctx;
+	int ret;
+
+	ctx = perf_event_ctx_lock(event);
+	ret = _perf_event_refresh(event, refresh);
+	perf_event_ctx_unlock(event, ctx);
+
+	return ret;
+}
 EXPORT_SYMBOL_GPL(perf_event_refresh);
 
 static void ctx_sched_out(struct perf_event_context *ctx,
@@ -3426,7 +3537,16 @@ static void perf_remove_from_owner(struct perf_event *event)
 	rcu_read_unlock();
 
 	if (owner) {
-		mutex_lock(&owner->perf_event_mutex);
+		/*
+		 * If we're here through perf_event_exit_task() we're already
+		 * holding ctx->mutex which would be an inversion wrt. the
+		 * normal lock order.
+		 *
+		 * However we can safely take this lock because its the child
+		 * ctx->mutex.
+		 */
+		mutex_lock_nested(&owner->perf_event_mutex, SINGLE_DEPTH_NESTING);
+
 		/*
 		 * We have to re-check the event->owner field, if it is cleared
 		 * we raced with perf_event_exit_task(), acquiring the mutex
@@ -3552,12 +3672,13 @@ static int perf_event_read_group(struct perf_event *event,
 				   u64 read_format, char __user *buf)
 {
 	struct perf_event *leader = event->group_leader, *sub;
-	int n = 0, size = 0, ret = -EFAULT;
 	struct perf_event_context *ctx = leader->ctx;
-	u64 values[5];
+	int n = 0, size = 0, ret;
 	u64 count, enabled, running;
+	u64 values[5];
+
+	lockdep_assert_held(&ctx->mutex);
 
-	mutex_lock(&ctx->mutex);
 	count = perf_event_read_value(leader, &enabled, &running);
 
 	values[n++] = 1 + leader->nr_siblings;
@@ -3572,7 +3693,7 @@ static int perf_event_read_group(struct perf_event *event,
 	size = n * sizeof(u64);
 
 	if (copy_to_user(buf, values, size))
-		goto unlock;
+		return -EFAULT;
 
 	ret = size;
 
@@ -3586,14 +3707,11 @@ static int perf_event_read_group(struct perf_event *event,
 		size = n * sizeof(u64);
 
 		if (copy_to_user(buf + ret, values, size)) {
-			ret = -EFAULT;
-			goto unlock;
+			return -EFAULT;
 		}
 
 		ret += size;
 	}
-unlock:
-	mutex_unlock(&ctx->mutex);
 
 	return ret;
 }
@@ -3665,8 +3783,14 @@ static ssize_t
 perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 {
 	struct perf_event *event = file->private_data;
+	struct perf_event_context *ctx;
+	int ret;
 
-	return perf_read_hw(event, buf, count);
+	ctx = perf_event_ctx_lock(event);
+	ret = perf_read_hw(event, buf, count);
+	perf_event_ctx_unlock(event, ctx);
+
+	return ret;
 }
 
 static unsigned int perf_poll(struct file *file, poll_table *wait)
@@ -3692,7 +3816,7 @@ static unsigned int perf_poll(struct file *file, poll_table *wait)
 	return events;
 }
 
-static void perf_event_reset(struct perf_event *event)
+static void _perf_event_reset(struct perf_event *event)
 {
 	(void)perf_event_read(event);
 	local64_set(&event->count, 0);
@@ -3711,6 +3835,7 @@ static void perf_event_for_each_child(struct perf_event *event,
 	struct perf_event *child;
 
 	WARN_ON_ONCE(event->ctx->parent_ctx);
+
 	mutex_lock(&event->child_mutex);
 	func(event);
 	list_for_each_entry(child, &event->child_list, child_list)
@@ -3724,14 +3849,13 @@ static void perf_event_for_each(struct perf_event *event,
 	struct perf_event_context *ctx = event->ctx;
 	struct perf_event *sibling;
 
-	WARN_ON_ONCE(ctx->parent_ctx);
-	mutex_lock(&ctx->mutex);
+	lockdep_assert_held(&ctx->mutex);
+
 	event = event->group_leader;
 
 	perf_event_for_each_child(event, func);
 	list_for_each_entry(sibling, &event->sibling_list, group_entry)
 		perf_event_for_each_child(sibling, func);
-	mutex_unlock(&ctx->mutex);
 }
 
 static int perf_event_period(struct perf_event *event, u64 __user *arg)
@@ -3801,25 +3925,24 @@ static int perf_event_set_output(struct perf_event *event,
 				 struct perf_event *output_event);
 static int perf_event_set_filter(struct perf_event *event, void __user *arg);
 
-static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned long arg)
 {
-	struct perf_event *event = file->private_data;
 	void (*func)(struct perf_event *);
 	u32 flags = arg;
 
 	switch (cmd) {
 	case PERF_EVENT_IOC_ENABLE:
-		func = perf_event_enable;
+		func = _perf_event_enable;
 		break;
 	case PERF_EVENT_IOC_DISABLE:
-		func = perf_event_disable;
+		func = _perf_event_disable;
 		break;
 	case PERF_EVENT_IOC_RESET:
-		func = perf_event_reset;
+		func = _perf_event_reset;
 		break;
 
 	case PERF_EVENT_IOC_REFRESH:
-		return perf_event_refresh(event, arg);
+		return _perf_event_refresh(event, arg);
 
 	case PERF_EVENT_IOC_PERIOD:
 		return perf_event_period(event, (u64 __user *)arg);
@@ -3866,6 +3989,19 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 	return 0;
 }
 
+static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct perf_event *event = file->private_data;
+	struct perf_event_context *ctx;
+	long ret;
+
+	ctx = perf_event_ctx_lock(event);
+	ret = _perf_ioctl(event, cmd, arg);
+	perf_event_ctx_unlock(event, ctx);
+
+	return ret;
+}
+
 #ifdef CONFIG_COMPAT
 static long perf_compat_ioctl(struct file *file, unsigned int cmd,
 				unsigned long arg)
@@ -3888,11 +4024,15 @@ static long perf_compat_ioctl(struct file *file, unsigned int cmd,
 
 int perf_event_task_enable(void)
 {
+	struct perf_event_context *ctx;
 	struct perf_event *event;
 
 	mutex_lock(&current->perf_event_mutex);
-	list_for_each_entry(event, &current->perf_event_list, owner_entry)
-		perf_event_for_each_child(event, perf_event_enable);
+	list_for_each_entry(event, &current->perf_event_list, owner_entry) {
+		ctx = perf_event_ctx_lock(event);
+		perf_event_for_each_child(event, _perf_event_enable);
+		perf_event_ctx_unlock(event, ctx);
+	}
 	mutex_unlock(&current->perf_event_mutex);
 
 	return 0;
@@ -3900,11 +4040,15 @@ int perf_event_task_enable(void)
 
 int perf_event_task_disable(void)
 {
+	struct perf_event_context *ctx;
 	struct perf_event *event;
 
 	mutex_lock(&current->perf_event_mutex);
-	list_for_each_entry(event, &current->perf_event_list, owner_entry)
-		perf_event_for_each_child(event, perf_event_disable);
+	list_for_each_entry(event, &current->perf_event_list, owner_entry) {
+		ctx = perf_event_ctx_lock(event);
+		perf_event_for_each_child(event, _perf_event_disable);
+		perf_event_ctx_unlock(event, ctx);
+	}
 	mutex_unlock(&current->perf_event_mutex);
 
 	return 0;
@@ -6927,6 +7071,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	if (!group_leader)
 		group_leader = event;
 
+	mutex_init(&event->group_leader_mutex);
 	mutex_init(&event->child_mutex);
 	INIT_LIST_HEAD(&event->child_list);
 
@@ -7203,6 +7348,15 @@ out:
 	return ret;
 }
 
+static void mutex_lock_double(struct mutex *a, struct mutex *b)
+{
+	if (b < a)
+		swap(a, b);
+
+	mutex_lock(a);
+	mutex_lock_nested(b, SINGLE_DEPTH_NESTING);
+}
+
 /**
  * sys_perf_event_open - open a performance event, associate it to a task/cpu
  *
@@ -7218,7 +7372,7 @@ SYSCALL_DEFINE5(perf_event_open,
 	struct perf_event *group_leader = NULL, *output_event = NULL;
 	struct perf_event *event, *sibling;
 	struct perf_event_attr attr;
-	struct perf_event_context *ctx;
+	struct perf_event_context *ctx, *uninitialized_var(gctx);
 	struct file *event_file = NULL;
 	struct fd group = {NULL, 0};
 	struct task_struct *task = NULL;
@@ -7279,6 +7433,16 @@ SYSCALL_DEFINE5(perf_event_open,
 			group_leader = NULL;
 	}
 
+	/*
+	 * Take the group_leader's group_leader_mutex before observing
+	 * anything in the group leader that leads to changes in ctx,
+	 * many of which may be changing on another thread.
+	 * In particular, we want to take this lock before deciding
+	 * whether we need to move_group.
+	 */
+	if (group_leader)
+		mutex_lock(&group_leader->group_leader_mutex);
+
 	if (pid != -1 && !(flags & PERF_FLAG_PID_CGROUP)) {
 		task = find_lively_task_by_vpid(pid);
 		if (IS_ERR(task)) {
@@ -7407,9 +7571,14 @@ SYSCALL_DEFINE5(perf_event_open,
 	}
 
 	if (move_group) {
-		struct perf_event_context *gctx = group_leader->ctx;
+		gctx = group_leader->ctx;
+
+		/*
+		 * See perf_event_ctx_lock() for comments on the details
+		 * of swizzling perf_event::ctx.
+		 */
+		mutex_lock_double(&gctx->mutex, &ctx->mutex);
 
-		mutex_lock(&gctx->mutex);
 		perf_remove_from_context(group_leader, false);
 
 		/*
@@ -7424,27 +7593,38 @@ SYSCALL_DEFINE5(perf_event_open,
 			perf_event__state_init(sibling);
 			put_ctx(gctx);
 		}
-		mutex_unlock(&gctx->mutex);
-		put_ctx(gctx);
+	} else {
+		mutex_lock(&ctx->mutex);
 	}
 
 	WARN_ON_ONCE(ctx->parent_ctx);
-	mutex_lock(&ctx->mutex);
 
 	if (move_group) {
+		/*
+		 * Wait for everybody to stop referencing the events through
+		 * the old lists, before installing it on new lists.
+		 */
 		synchronize_rcu();
-		perf_install_in_context(ctx, group_leader, event->cpu);
+
+		perf_install_in_context(ctx, group_leader, group_leader->cpu);
 		get_ctx(ctx);
 		list_for_each_entry(sibling, &group_leader->sibling_list,
 				    group_entry) {
-			perf_install_in_context(ctx, sibling, event->cpu);
+			perf_install_in_context(ctx, sibling, sibling->cpu);
 			get_ctx(ctx);
 		}
 	}
 
 	perf_install_in_context(ctx, event, event->cpu);
 	perf_unpin_context(ctx);
+
+	if (move_group) {
+		mutex_unlock(&gctx->mutex);
+		put_ctx(gctx);
+	}
 	mutex_unlock(&ctx->mutex);
+	if (group_leader)
+		mutex_unlock(&group_leader->group_leader_mutex);
 
 	put_online_cpus();
 
@@ -7481,6 +7661,8 @@ err_task:
 	if (task)
 		put_task_struct(task);
 err_group_fd:
+	if (group_leader)
+		mutex_unlock(&group_leader->group_leader_mutex);
 	fdput(group);
 err_fd:
 	put_unused_fd(event_fd);
@@ -7551,7 +7733,11 @@ void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
 	src_ctx = &per_cpu_ptr(pmu->pmu_cpu_context, src_cpu)->ctx;
 	dst_ctx = &per_cpu_ptr(pmu->pmu_cpu_context, dst_cpu)->ctx;
 
-	mutex_lock(&src_ctx->mutex);
+	/*
+	 * See perf_event_ctx_lock() for comments on the details
+	 * of swizzling perf_event::ctx.
+	 */
+	mutex_lock_double(&src_ctx->mutex, &dst_ctx->mutex);
 	list_for_each_entry_safe(event, tmp, &src_ctx->event_list,
 				 event_entry) {
 		perf_remove_from_context(event, false);
@@ -7559,11 +7745,9 @@ void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
 		put_ctx(src_ctx);
 		list_add(&event->migrate_entry, &events);
 	}
-	mutex_unlock(&src_ctx->mutex);
 
 	synchronize_rcu();
 
-	mutex_lock(&dst_ctx->mutex);
 	list_for_each_entry_safe(event, tmp, &events, migrate_entry) {
 		list_del(&event->migrate_entry);
 		if (event->state >= PERF_EVENT_STATE_OFF)
@@ -7573,6 +7757,7 @@ void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
 		get_ctx(dst_ctx);
 	}
 	mutex_unlock(&dst_ctx->mutex);
+	mutex_unlock(&src_ctx->mutex);
 }
 EXPORT_SYMBOL_GPL(perf_pmu_migrate_context);