From: Todd Kjos tkjos@android.com
commit 26528be6720bb40bc8844e97ee73a37e530e9c5e upstream.
Fixes crash found by syzbot: kernel BUG at drivers/android/binder_alloc.c:LINE! (2)
Reported-and-tested-by: syzbot+55de1eb4975dec156d8f@syzkaller.appspotmail.com Signed-off-by: Todd Kjos tkjos@google.com Reviewed-by: Joel Fernandes (Google) joel@joelfernandes.org Cc: stable stable@vger.kernel.org # 5.0, 4.19, 4.14 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- 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);