From: Todd Kjos <tkjos@xxxxxxxxxxx>
commit 26528be6720bb40bc8844e97ee73a37e530e9c5e upstream.
Fixes crash found by syzbot:
kernel BUG at drivers/android/binder_alloc.c:LINE! (2)
Reported-and-tested-by: syzbot+55de1eb4975dec156d8f@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Todd Kjos <tkjos@xxxxxxxxxx>
Reviewed-by: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxxxxxxx> # 5.0, 4.19, 4.14
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/android/binder_alloc.c | 18 ++++++++----------
1 file changed, 8 insertions(+), 10 deletions(-)
--- a/drivers/android/binder_alloc.c
+++ b/drivers/android/binder_alloc.c
@@ -959,14 +959,13 @@ enum lru_status binder_alloc_free_page(s
index = page - alloc->pages;
page_addr = (uintptr_t)alloc->buffer + index * PAGE_SIZE;
+
+ mm = alloc->vma_vm_mm;
+ if (!mmget_not_zero(mm))
+ goto err_mmget;
+ if (!down_write_trylock(&mm->mmap_sem))
+ goto err_down_write_mmap_sem_failed;
vma = binder_alloc_get_vma(alloc);
- if (vma) {
- if (!mmget_not_zero(alloc->vma_vm_mm))
- goto err_mmget;
- mm = alloc->vma_vm_mm;
- if (!down_write_trylock(&mm->mmap_sem))
- goto err_down_write_mmap_sem_failed;
- }
list_lru_isolate(lru, item);
spin_unlock(lock);
@@ -979,10 +978,9 @@ enum lru_status binder_alloc_free_page(s
PAGE_SIZE);
trace_binder_unmap_user_end(alloc, index);
-
- up_write(&mm->mmap_sem);
- mmput(mm);
}
+ up_write(&mm->mmap_sem);
+ mmput(mm);
trace_binder_unmap_kernel_start(alloc, index);
