linux-kernel - [PATCH 6/8] binder: remove cached alloc->vma pointer

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Message-ID: <20241105200258.2380168-7-cmllamas@google.com>
Date: Tue,  5 Nov 2024 20:02:48 +0000
From: Carlos Llamas <cmllamas@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	"Arve Hjønnevåg" <arve@...roid.com>, Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joel@...lfernandes.org>, Christian Brauner <brauner@...nel.org>, 
	Carlos Llamas <cmllamas@...gle.com>, Suren Baghdasaryan <surenb@...gle.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...roid.com, 
	Minchan Kim <minchan@...nel.org>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Matthew Wilcox <willy@...radead.org>
Subject: [PATCH 6/8] binder: remove cached alloc->vma pointer

All usage of the alloc->vma pointer has been removed from binder.
Instead, paths has been refactored to use either vma_lookup() or the
alloc->mapped state. Using the alloc->vma was unsafe and required the
mmap_sem in exclusive mode, which caused several performance and
security issues in the past.

Cc: Minchan Kim <minchan@...nel.org>
Cc: Liam R. Howlett <Liam.Howlett@...cle.com>
Cc: Matthew Wilcox <willy@...radead.org>
Cc: Suren Baghdasaryan <surenb@...gle.com>
Signed-off-by: Carlos Llamas <cmllamas@...gle.com>
---
 drivers/android/binder_alloc.c | 14 --------------
 drivers/android/binder_alloc.h |  3 ---
 2 files changed, 17 deletions(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index aa299cbdab92..a4b7bf8696dd 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -369,20 +369,6 @@ static void binder_lru_freelist_del(struct binder_alloc *alloc,
 	}
 }
 
-static inline void binder_alloc_set_vma(struct binder_alloc *alloc,
-		struct vm_area_struct *vma)
-{
-	/* pairs with smp_load_acquire in binder_alloc_get_vma() */
-	smp_store_release(&alloc->vma, vma);
-}
-
-static inline struct vm_area_struct *binder_alloc_get_vma(
-		struct binder_alloc *alloc)
-{
-	/* pairs with smp_store_release in binder_alloc_set_vma() */
-	return smp_load_acquire(&alloc->vma);
-}
-
 static void debug_no_space_locked(struct binder_alloc *alloc)
 {
 	size_t largest_alloc_size = 0;
diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index 89f6fa25c670..b9e2e9dc90b3 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -61,8 +61,6 @@ struct binder_buffer {
 /**
  * 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
@@ -86,7 +84,6 @@ struct binder_buffer {
  */
 struct binder_alloc {
 	struct mutex mutex;
-	struct vm_area_struct *vma;
 	struct mm_struct *mm;
 	unsigned long buffer;
 	struct list_head buffers;
-- 
2.47.0.199.ga7371fff76-goog