From c0fd2101781ef761b636769b2f445351f71c3626 Mon Sep 17 00:00:00 2001 From: Carlos Llamas Date: Tue, 2 May 2023 20:12:18 +0000 Subject: 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 Cc: Suren Baghdasaryan Cc: stable@vger.kernel.org Signed-off-by: Carlos Llamas Link: https://lore.kernel.org/r/20230502201220.1756319-2-cmllamas@google.com Signed-off-by: Greg Kroah-Hartman --- drivers/android/binder_alloc.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) (limited to 'drivers/android/binder_alloc.c') 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; } /** -- cgit v1.2.3