在 2016/8/18 23:23, Greg Kroah-Hartman 写道:
On Tue, Aug 16, 2016 at 07:44:59PM -0700, Arve Hjønnevåg wrote:
On Mon, Aug 15, 2016 at 7:58 AM, Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
On Thu, Jun 16, 2016 at 12:45:33AM +0200, Jann Horn wrote:
If /dev/binder is opened and the opener process then e.g. calls execve,
proc->vma_vm_mm will still point to the location of the now-freed
mm_struct. If the process then calls ioctl(binder_fd, ...), the dangling
proc->vma_vm_mm pointer will be compared to current->mm.
Let the binder take a reference to the mm_struct to avoid this.
v2: use the right refcounter
Fixes: a906d6931f3ccaf7de805643190765ddd7378e27
Nit, the proper way to do this is:
Fixes: a906d6931f3c ("android: binder: Sanity check at binder ioctl")
You can get that by doing:
git show -s --abbrev-commit --abbrev=12 --pretty=format:"%h (\"%s\")%n" a906d6931f3ccaf7de805643190765ddd7378e27
Also, I'm guessing this should go to the stable kernels that include the
above patch?
Has this patch been tested?
Hi:
The patch have tested in huawei device.
Does it actually fix anything?
Changes to vma_vm_mm are normally protected by the mmap_sem it
contains, and is set to NULL in the vma->vm_ops->close call on the
binder vma. The vma_vm_mm pointer is only used to check if the mm
struct that the binder driver was mmapped into is the same mm struct
that the driver just locked (in binder_update_page_range). I don't
think change description here is accurate. If a process calls execve,
the old vma should be closed (and vma_vm_mm cleared) before the
mm_struct that it belongs too is freed.
Yeah, this whole thing feels wrong...
In huawei device,
For example: system_server process use many libs,libstagefright,
Libdrmframework etc.
In these lib, binder global object exist like static sp<DeathNotifier>
sDeathNotifier, static sp<IDrmManagerService> sDrmManagerService;
When system_sever process fork failed, the new child process call exit,
which will call hook destruction function.
In destruction, the parent process *binder reference count will be
wrong*. To protect
these exception, we need to add the code in binder.
Combined with the original author's email address now bouncing, so I've
reverted this patch from the tree.
thanks,
greg k-h
.
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