This is a note to let you know that I've just added the patch titled
Revert "android: binder: stop saving a pointer to the VMA"
to the 6.3-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-android-binder-stop-saving-a-pointer-to-the-vma.patch
and it can be found in the queue-6.3 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From c0fd2101781ef761b636769b2f445351f71c3626 Mon Sep 17 00:00:00 2001
From: Carlos Llamas <cmllamas@xxxxxxxxxx>
Date: Tue, 2 May 2023 20:12:18 +0000
Subject: Revert "android: binder: stop saving a pointer to the VMA"
From: Carlos Llamas <cmllamas@xxxxxxxxxx>
commit c0fd2101781ef761b636769b2f445351f71c3626 upstream.
This reverts commit a43cfc87caaf46710c8027a8c23b8a55f1078f19.
This patch fixed an issue reported by syzkaller in [1]. However, this
turned out to be only a band-aid in binder. The root cause, as bisected
by syzkaller, was fixed by commit 5789151e48ac ("mm/mmap: undo ->mmap()
when mas_preallocate() fails"). We no longer need the patch for binder.
Reverting such patch allows us to have a lockless access to alloc->vma
in specific cases where the mmap_lock is not required. This approach
avoids the contention that caused a performance regression.
[1] https://lore.kernel.org/all/0000000000004a0dbe05e1d749e0@xxxxxxxxxx
[cmllamas: resolved conflicts with rework of alloc->mm and removal of
binder_alloc_set_vma() also fixed comment section]
Fixes: a43cfc87caaf ("android: binder: stop saving a pointer to the VMA")
Cc: Liam Howlett <liam.howlett@xxxxxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Carlos Llamas <cmllamas@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230502201220.1756319-2-cmllamas@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/android/binder_alloc.c | 17 +++++++++--------
drivers/android/binder_alloc.h | 4 ++--
drivers/android/binder_alloc_selftest.c | 2 +-
3 files changed, 12 insertions(+), 11 deletions(-)
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -213,7 +213,7 @@ static int binder_update_page_range(stru
if (mm) {
mmap_read_lock(mm);
- vma = vma_lookup(mm, alloc->vma_addr);
+ vma = alloc->vma;
}
if (!vma && need_mm) {
@@ -314,9 +314,11 @@ static inline struct vm_area_struct *bin
{
struct vm_area_struct *vma = NULL;
- if (alloc->vma_addr)
- vma = vma_lookup(alloc->mm, alloc->vma_addr);
-
+ if (alloc->vma) {
+ /* Look at description in binder_alloc_set_vma */
+ smp_rmb();
+ vma = alloc->vma;
+ }
return vma;
}
@@ -775,7 +777,7 @@ int binder_alloc_mmap_handler(struct bin
buffer->free = 1;
binder_insert_free_buffer(alloc, buffer);
alloc->free_async_space = alloc->buffer_size / 2;
- alloc->vma_addr = vma->vm_start;
+ alloc->vma = vma;
return 0;
@@ -805,8 +807,7 @@ void binder_alloc_deferred_release(struc
buffers = 0;
mutex_lock(&alloc->mutex);
- BUG_ON(alloc->vma_addr &&
- vma_lookup(alloc->mm, alloc->vma_addr));
+ BUG_ON(alloc->vma);
while ((n = rb_first(&alloc->allocated_buffers))) {
buffer = rb_entry(n, struct binder_buffer, rb_node);
@@ -958,7 +959,7 @@ int binder_alloc_get_allocated_count(str
*/
void binder_alloc_vma_close(struct binder_alloc *alloc)
{
- alloc->vma_addr = 0;
+ alloc->vma = 0;
}
/**
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -75,7 +75,7 @@ struct binder_lru_page {
/**
* struct binder_alloc - per-binder proc state for binder allocator
* @mutex: protects binder_alloc fields
- * @vma_addr: vm_area_struct->vm_start passed to mmap_handler
+ * @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
@@ -99,7 +99,7 @@ struct binder_lru_page {
*/
struct binder_alloc {
struct mutex mutex;
- unsigned long vma_addr;
+ struct vm_area_struct *vma;
struct mm_struct *mm;
void __user *buffer;
struct list_head buffers;
--- a/drivers/android/binder_alloc_selftest.c
+++ b/drivers/android/binder_alloc_selftest.c
@@ -287,7 +287,7 @@ void binder_selftest_alloc(struct binder
if (!binder_selftest_run)
return;
mutex_lock(&binder_selftest_lock);
- if (!binder_selftest_run || !alloc->vma_addr)
+ if (!binder_selftest_run || !alloc->vma)
goto done;
pr_info("STARTED\n");
binder_selftest_alloc_offset(alloc, end_offset, 0);
Patches currently in stable-queue which might be from cmllamas@xxxxxxxxxx are
queue-6.3/revert-android-binder-stop-saving-a-pointer-to-the-vma.patch
queue-6.3/binder-fix-uaf-of-alloc-vma-in-race-with-munmap.patch
queue-6.3/binder-fix-uaf-caused-by-faulty-buffer-cleanup.patch
queue-6.3/revert-binder_alloc-add-missing-mmap_lock-calls-when-using-the-vma.patch
queue-6.3/binder-add-lockless-binder_alloc_-set-get-_vma.patch
