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@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 [cmllamas: fixed merge conflict in binder_alloc_set_vma()] Signed-off-by: Carlos Llamas cmllamas@google.com --- drivers/android/binder_alloc.c | 27 ++++++++++++------------- drivers/android/binder_alloc.h | 2 +- drivers/android/binder_alloc_selftest.c | 2 +- 3 files changed, 15 insertions(+), 16 deletions(-)
diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index f1dc5326a1d9..3cfad638db63 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) { @@ -313,14 +313,12 @@ static int binder_update_page_range(struct binder_alloc *alloc, int allocate, static inline void binder_alloc_set_vma(struct binder_alloc *alloc, struct vm_area_struct *vma) { - unsigned long vm_start = 0; - - if (vma) { - vm_start = vma->vm_start; - mmap_assert_write_locked(alloc->vma_vm_mm); - } - - alloc->vma_addr = vm_start; + /* + * If we see alloc->vma is not NULL, buffer data structures set up + * completely. Look at smp_rmb side binder_alloc_get_vma. + */ + smp_wmb(); + alloc->vma = vma; }
static inline struct vm_area_struct *binder_alloc_get_vma( @@ -328,9 +326,11 @@ static inline struct vm_area_struct *binder_alloc_get_vma( { struct vm_area_struct *vma = NULL;
- if (alloc->vma_addr) - vma = vma_lookup(alloc->vma_vm_mm, alloc->vma_addr); - + if (alloc->vma) { + /* Look at description in binder_alloc_set_vma */ + smp_rmb(); + vma = alloc->vma; + } return vma; }
@@ -819,8 +819,7 @@ void binder_alloc_deferred_release(struct binder_alloc *alloc)
buffers = 0; mutex_lock(&alloc->mutex); - BUG_ON(alloc->vma_addr && - vma_lookup(alloc->vma_vm_mm, alloc->vma_addr)); + BUG_ON(alloc->vma);
while ((n = rb_first(&alloc->allocated_buffers))) { buffer = rb_entry(n, struct binder_buffer, rb_node); diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h index 1e4fd37af5e0..7dea57a84c79 100644 --- a/drivers/android/binder_alloc.h +++ b/drivers/android/binder_alloc.h @@ -100,7 +100,7 @@ struct binder_lru_page { */ struct binder_alloc { struct mutex mutex; - unsigned long vma_addr; + struct vm_area_struct *vma; struct mm_struct *vma_vm_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);