On Thu, Aug 18, 2016 at 08:00:59PM -0700, Arve Hjønnevåg wrote:
> On Thu, Aug 18, 2016 at 7:30 PM, ZhaoJunmin Zhao(Junmin)
> <zhaojunmin@xxxxxxxxxx> wrote:
> >
> >
> > 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.
>
> I not sure I follow this.
>
> I see now that there is another patch that got merged that reused the
> vma_vm_mm in the ioctl itself, without holding the lock that protects
> it in the existing code. It would probably be best to revert that
> change too.
So what other patch should I revert? Have a git commit id?
thanks,
greg k-h
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