Re: [PATCH v4] usb: gadget: f_fs: try to fix AIO issue under ARM 64 bit TAGGED mode

Catalin Marinas
2020-03-02T16:19:37Z

On Sun, Mar 01, 2020 at 11:20:43AM +0800, Macpaul Lin wrote:
> On Fri, 2020-02-28 at 16:48 +0000, Catalin Marinas wrote:
> > On Wed, Feb 26, 2020 at 08:01:52PM +0800, Macpaul Lin wrote:
> > > diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
> > > index ce1d023..192935f 100644
> > > --- a/drivers/usb/gadget/function/f_fs.c
> > > +++ b/drivers/usb/gadget/function/f_fs.c
> > > @@ -715,7 +715,20 @@ static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
> > >
> > > static ssize_t ffs_copy_to_iter(void *data, int data_len, struct iov_iter *iter)
> > > {
> > > - ssize_t ret = copy_to_iter(data, data_len, iter);
> > > + ssize_t ret;
> > > +
> > > +#if defined(CONFIG_ARM64)
> > > + /*
> > > + * Replace tagged address passed by user space application before
> > > + * copying.
> > > + */
> > > + if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
> > > + (iter->type == ITER_IOVEC)) {
> > > + *(unsigned long *)&iter->iov->iov_base =
> > > + (unsigned long)untagged_addr(iter->iov->iov_base);
> > > + }
> > > +#endif
> > > + ret = copy_to_iter(data, data_len, iter);
> > > if (likely(ret == data_len))
> > > return ret;
> >
> > I had forgotten that we discussed a similar case already a few months
> > ago (thanks to Evgenii for pointing out). Do you have this commit
> > applied to your tree: df325e05a682 ("arm64: Validate tagged addresses in
> > access_ok() called from kernel threads")?
> >
>
> Yes! We have that patch. I've also got Google's reply about referencing
> this patch in android kernel tree.
> https://android-review.googlesource.com/c/kernel/common/+/1186615
>
> However, during my debugging process, I've dumped specific length (e.g.,
> 24 bytes for the first request) AIO request buffer address both in adbd
> and in __range_ok(). Then I've found __range_ok() still always return
> false on address begin with "0x3c". Since untagged_addr() already called
> in __range_ok(), to set "TIF_TAGGED_ADDR" with adbd's user space buffer
> should be the possible solution. Hence I've send the v3 patch.

ffs_copy_to_iter() is called from a workqueue (ffs_user_copy_worker()).
That's still in a kernel thread context but it doesn't have PF_KTHREAD
set, hence __range_ok() rejects the tagged address. Can you try the diff
below:

diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h
index 32fc8061aa76..2803143cad1f 100644
--- a/arch/arm64/include/asm/uaccess.h
+++ b/arch/arm64/include/asm/uaccess.h
@@ -68,7 +68,8 @@ static inline unsigned long __range_ok(const void __user *addr, unsigned long si
* the user address before checking.
*/
if (IS_ENABLED(CONFIG_ARM64_TAGGED_ADDR_ABI) &&
- (current->flags & PF_KTHREAD || test_thread_flag(TIF_TAGGED_ADDR)))
+ (current->flags & (PF_KTHREAD | PF_WQ_WORKER) ||
+ test_thread_flag(TIF_TAGGED_ADDR)))
addr = untagged_addr(addr);

__chk_user_ptr(addr);
-