On 05/24/2017 05:51 PM, Dmitry Safonov wrote:
> binder_mmap() protected proc->buffer from concurrent changes.
> It was introduced with commit bd1eff9741af ("Staging: android: binder:
> Fix crashes when sharing a binder file between processes").
>
> The commit fixed such races alike:
>
> task1
> =====
> fd = open("/dev/binder",..)
> fork()
> ---------------------------------------->task2
> | =====
> mmap(fd) mmap(fd)
>
> Afterwards the situation was changed with the commit a79f41ed9786
> ("binder: don't allow mmap() by process other than proc->tsk").
> That commit prohibited mmap'ing of fd, that was opened by some
> other task.
> That restriction has made locking in binder_mmap() unnecessary.
>
> Cc: Al Viro <[email protected]>
> Cc: "Arve Hjønnevåg" <[email protected]>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: Riley Andrews <[email protected]>
> Cc: [email protected]
> Cc: Android Kernel Team <[email protected]>
> Signed-off-by: Dmitry Safonov <[email protected]>
> ---
> drivers/android/binder.c | 5 -----
> 1 file changed, 5 deletions(-)
Ping?
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index aae4d8d4be36..b5b32be85ab8 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -49,7 +49,6 @@
>
> static DEFINE_MUTEX(binder_main_lock);
> static DEFINE_MUTEX(binder_deferred_lock);
> -static DEFINE_MUTEX(binder_mmap_lock);
>
> static HLIST_HEAD(binder_devices);
> static HLIST_HEAD(binder_procs);
> @@ -3381,7 +3380,6 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
> }
> vma->vm_flags = (vma->vm_flags | VM_DONTCOPY) & ~VM_MAYWRITE;
>
> - mutex_lock(&binder_mmap_lock);
> if (proc->buffer) {
> ret = -EBUSY;
> failure_string = "already mapped";
> @@ -3396,7 +3394,6 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
> }
> proc->buffer = area->addr;
> proc->user_buffer_offset = vma->vm_start - (uintptr_t)proc->buffer;
> - mutex_unlock(&binder_mmap_lock);
>
> #ifdef CONFIG_CPU_CACHE_VIPT
> if (cache_is_vipt_aliasing()) {
> @@ -3441,12 +3438,10 @@ static int binder_mmap(struct file *filp, struct vm_area_struct *vma)
> kfree(proc->pages);
> proc->pages = NULL;
> err_alloc_pages_failed:
> - mutex_lock(&binder_mmap_lock);
> vfree(proc->buffer);
> proc->buffer = NULL;
> err_get_vm_area_failed:
> err_already_mapped:
> - mutex_unlock(&binder_mmap_lock);
> err_bad_arg:
> pr_err("binder_mmap: %d %lx-%lx %s failed %d\n",
> proc->pid, vma->vm_start, vma->vm_end, failure_string, ret);
>
On Mon, Jun 19, 2017 at 05:53:34PM +0300, Dmitry Safonov wrote:
> On 05/24/2017 05:51 PM, Dmitry Safonov wrote:
> > binder_mmap() protected proc->buffer from concurrent changes.
> > It was introduced with commit bd1eff9741af ("Staging: android: binder:
> > Fix crashes when sharing a binder file between processes").
> >
> > The commit fixed such races alike:
> >
> > task1
> > =====
> > fd = open("/dev/binder",..)
> > fork()
> > ---------------------------------------->task2
> > | =====
> > mmap(fd) mmap(fd)
> >
> > Afterwards the situation was changed with the commit a79f41ed9786
> > ("binder: don't allow mmap() by process other than proc->tsk").
> > That commit prohibited mmap'ing of fd, that was opened by some
> > other task.
> > That restriction has made locking in binder_mmap() unnecessary.
> >
> > Cc: Al Viro <[email protected]>
> > Cc: "Arve Hj?nnev?g" <[email protected]>
> > Cc: Greg Kroah-Hartman <[email protected]>
> > Cc: Riley Andrews <[email protected]>
> > Cc: [email protected]
> > Cc: Android Kernel Team <[email protected]>
> > Signed-off-by: Dmitry Safonov <[email protected]>
> > ---
> > drivers/android/binder.c | 5 -----
> > 1 file changed, 5 deletions(-)
>
> Ping?
The "break up the binder lock" patches should have now made this
obsolete, right? If not, can you please rebase it on my
char-misc-testing tree and resend?
thanks,
greg k-h