binder: replace alloc->vma with alloc->mapped

It is unsafe to use alloc->vma outside of the mmap_sem. Instead, add a
new boolean alloc->mapped to save the vma state (mapped or unmmaped) and
use this as a replacement for alloc->vma to validate several paths.

Using the alloc->vma caused several performance and security issues in
the past. Now that it has been replaced with either vm_lookup() or the
alloc->mapped state, we can finally remove it.

Cc: Minchan Kim <minchan@kernel.org>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20241210143114.661252-6-cmllamas@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index d71f99189ef5c..3ebb12afd4de4 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -82,8 +82,6 @@ static inline struct list_head *page_to_lru(struct page *p)
 /**
  * struct binder_alloc - per-binder proc state for binder allocator
  * @mutex:              protects binder_alloc fields
- * @vma:                vm_area_struct passed to mmap_handler
- *                      (invariant after mmap)
  * @mm:                 copy of task->mm (invariant after open)
  * @buffer:             base of per-proc address space mapped via mmap
  * @buffers:            list of all buffers for this proc
@@ -96,6 +94,8 @@ static inline struct list_head *page_to_lru(struct page *p)
  * @buffer_size:        size of address space specified via mmap
  * @pid:                pid for associated binder_proc (invariant after init)
  * @pages_high:         high watermark of offset in @pages
+ * @mapped:             whether the vm area is mapped, each binder instance is
+ *                      allowed a single mapping throughout its lifetime
  * @oneway_spam_detected: %true if oneway spam detection fired, clear that
  * flag once the async buffer has returned to a healthy state
  *
@@ -106,7 +106,6 @@ static inline struct list_head *page_to_lru(struct page *p)
  */
 struct binder_alloc {
 	struct mutex mutex;
-	struct vm_area_struct *vma;
 	struct mm_struct *mm;
 	unsigned long buffer;
 	struct list_head buffers;
@@ -117,6 +116,7 @@ struct binder_alloc {
 	size_t buffer_size;
 	int pid;
 	size_t pages_high;
+	bool mapped;
 	bool oneway_spam_detected;
 };