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authorCarlos Llamas <cmllamas@google.com>2023-05-02 23:12:18 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2023-05-13 14:30:16 +0300
commitc0fd2101781ef761b636769b2f445351f71c3626 (patch)
tree093d23560158ab82210ba65e57f9232902ff2c6e /drivers/android
parentb15655b12ddca7ade09807f790bafb6fab61b50a (diff)
downloadlinux-c0fd2101781ef761b636769b2f445351f71c3626.tar.xz
Revert "android: binder: stop saving a pointer to the VMA"
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@google.com [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@oracle.com> Cc: Suren Baghdasaryan <surenb@google.com> Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas <cmllamas@google.com> Link: https://lore.kernel.org/r/20230502201220.1756319-2-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/android')
-rw-r--r--drivers/android/binder_alloc.c17
-rw-r--r--drivers/android/binder_alloc.h4
-rw-r--r--drivers/android/binder_alloc_selftest.c2
3 files changed, 12 insertions, 11 deletions
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c
index 92c814ec44fe..eb082b33115b 100644
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -213,7 +213,7 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate,
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 *binder_alloc_get_vma(
{
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 binder_alloc *alloc,
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(struct binder_alloc *alloc)
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(struct binder_alloc *alloc)
*/
void binder_alloc_vma_close(struct binder_alloc *alloc)
{
- alloc->vma_addr = 0;
+ alloc->vma = 0;
}
/**
diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index 0f811ac4bcff..138d1d5af9ce 100644
--- 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;
diff --git a/drivers/android/binder_alloc_selftest.c b/drivers/android/binder_alloc_selftest.c
index 43a881073a42..c2b323bc3b3a 100644
--- a/drivers/android/binder_alloc_selftest.c
+++ b/drivers/android/binder_alloc_selftest.c
@@ -287,7 +287,7 @@ void binder_selftest_alloc(struct binder_alloc *alloc)
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);