From 2a90957f2cfc2bf0b705a62a97830cf0d42a5a40 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Arve=20Hj=C3=B8nnev=C3=A5g?= Date: Thu, 8 Mar 2012 15:43:36 -0800 Subject: [PATCH] Staging: android: binder: Fix use-after-free bug MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit binder_update_page_range could read freed memory if the vma of the selected process was freed right before the check that the vma belongs to the mm struct it just locked. If the vm_mm pointer in that freed vma struct had also been rewritten with a value that matched the locked mm struct, then the code would proceed and possibly modify the freed vma. Signed-off-by: Arve Hjønnevåg Signed-off-by: Greg Kroah-Hartman --- drivers/staging/android/binder.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/staging/android/binder.c b/drivers/staging/android/binder.c index 6db1c1bfeb98..59e095362c81 100644 --- a/drivers/staging/android/binder.c +++ b/drivers/staging/android/binder.c @@ -288,6 +288,7 @@ struct binder_proc { struct rb_root refs_by_node; int pid; struct vm_area_struct *vma; + struct mm_struct *vma_vm_mm; struct task_struct *tsk; struct files_struct *files; struct hlist_node deferred_work_node; @@ -633,7 +634,7 @@ static int binder_update_page_range(struct binder_proc *proc, int allocate, if (mm) { down_write(&mm->mmap_sem); vma = proc->vma; - if (vma && mm != vma->vm_mm) { + if (vma && mm != proc->vma_vm_mm) { pr_err("binder: %d: vma mm and task mm mismatch\n", proc->pid); vma = NULL; @@ -2776,6 +2777,7 @@ static void binder_vma_close(struct vm_area_struct *vma) (vma->vm_end - vma->vm_start) / SZ_1K, vma->vm_flags, (unsigned long)pgprot_val(vma->vm_page_prot)); proc->vma = NULL; + proc->vma_vm_mm = NULL; binder_defer_work(proc, BINDER_DEFERRED_PUT_FILES); } @@ -2858,6 +2860,7 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma) barrier(); proc->files = get_files_struct(proc->tsk); proc->vma = vma; + proc->vma_vm_mm = vma->vm_mm; /*printk(KERN_INFO "binder_mmap: %d %lx-%lx maps %p\n", proc->pid, vma->vm_start, vma->vm_end, proc->buffer);*/