perf/core: Exit early on perf_mmap() fail

When perf_mmap() fails to allocate a buffer, it still invokes the
event_mapped() callback of the related event. On X86 this might increase
the perf_rdpmc_allowed reference counter. But nothing undoes this as
perf_mmap_close() is never called in this case, which causes another
reference count leak.

Return early on failure to prevent that.

Fixes: 1e0fb9e ("perf: Add pmu callbacks to track event mapping and unmapping")
Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Lorenzo Stoakes <[email protected]>
Cc: [email protected]

Author: KAGA-KOKO

kernel/events/core.c

@@ -7138,15 +7138,17 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 		mutex_unlock(aux_mutex);
 	mutex_unlock(&event->mmap_mutex);
 
+	if (ret)
+		return ret;
+
 	/*
 	 * Since pinned accounting is per vm we cannot allow fork() to copy our
 	 * vma.
 	 */
 	vm_flags_set(vma, VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP);
 	vma->vm_ops = &perf_mmap_vmops;
 
-	if (!ret)
-		ret = map_range(rb, vma);
+	ret = map_range(rb, vma);
 
 	mapped = get_mapped(event, event_mapped);
 	if (mapped)