diff options
| author | Lars-Peter Clausen <lars@metafoo.de> | 2018-01-12 11:05:02 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2018-05-25 16:17:41 +0200 |
| commit | dd5541c7a60d9fe8715a0b7f90dbdac6c2457636 (patch) | |
| tree | d09c99691308b0386f05bc5abcdc4b498462cbfe /drivers/usb/gadget/function | |
| parent | 7f48c9ddca72a0c488331e775d21fe280c1f71f1 (diff) | |
usb: gadget: ffs: Execute copy_to_user() with USER_DS set
[ Upstream commit 4058ebf33cb0be88ca516f968eda24ab7b6b93e4 ]
When using a AIO read() operation on the function FS gadget driver a URB is
submitted asynchronously and on URB completion the received data is copied
to the userspace buffer associated with the read operation.
This is done from a kernel worker thread invoking copy_to_user() (through
copy_to_iter()). And while the user space process memory is made available
to the kernel thread using use_mm(), some architecture require in addition
to this that the operation runs with USER_DS set. Otherwise the userspace
memory access will fail.
For example on ARM64 with Privileged Access Never (PAN) and User Access
Override (UAO) enabled the following crash occurs.
Internal error: Accessing user space memory with fs=KERNEL_DS: 9600004f [#1] SMP
Modules linked in:
CPU: 2 PID: 1636 Comm: kworker/2:1 Not tainted 4.9.0-04081-g8ab2dfb-dirty #487
Hardware name: ZynqMP ZCU102 Rev1.0 (DT)
Workqueue: events ffs_user_copy_worker
task: ffffffc87afc8080 task.stack: ffffffc87a00c000
PC is at __arch_copy_to_user+0x190/0x220
LR is at copy_to_iter+0x78/0x3c8
[...]
[<ffffff800847b790>] __arch_copy_to_user+0x190/0x220
[<ffffff80086f25d8>] ffs_user_copy_worker+0x70/0x130
[<ffffff80080b8c64>] process_one_work+0x1dc/0x460
[<ffffff80080b8f38>] worker_thread+0x50/0x4b0
[<ffffff80080bf5a0>] kthread+0xd8/0xf0
[<ffffff8008083680>] ret_from_fork+0x10/0x50
Address this by placing a set_fs(USER_DS) before of the copy operation
and revert it again once the copy operation has finished.
This patch is analogous to commit d7ffde35e31a ("vhost: use USER_DS in
vhost_worker thread") which addresses the same underlying issue.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/gadget/function')
| -rw-r--r-- | drivers/usb/gadget/function/f_fs.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index a38609d15a31..7b53ac548b1a 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -759,9 +759,13 @@ static void ffs_user_copy_worker(struct work_struct *work) bool kiocb_has_eventfd = io_data->kiocb->ki_flags & IOCB_EVENTFD; if (io_data->read && ret > 0) { + mm_segment_t oldfs = get_fs(); + + set_fs(USER_DS); use_mm(io_data->mm); ret = ffs_copy_to_iter(io_data->buf, ret, &io_data->data); unuse_mm(io_data->mm); + set_fs(oldfs); } io_data->kiocb->ki_complete(io_data->kiocb, ret, ret); |