b2c4d95cb4
Starting from commit 'a6bfb6d13f33 ("mt76: usb: use max packet length
for m76u_copy")' reg_val does not share memory with usb data buffer.
On non-coherent devices this approach can corrupt data pointer since data
and reg_val share the same cache-line, resulting in the following crash:
[ 371.544901] CPU 0 Unable to handle kernel paging request at virtual address 00000000, epc == 8042fbb0
[ 371.558521] CPU: 0 PID: 11 Comm: kworker/u2:2 Not tainted 4.14.160 #0
[ 371.565204] Workqueue: mt76u mt76u_deinit [mt76_usb]
[ 371.570331] task: 83823ac0 task.stack: 8386c000
[ 371.575004] $ 0 : 00000000 80590000 00000000 00000000
[ 371.580407] $ 4 : 82edaad0 00000002 83823ac0 fffffff8
[ 371.585810] $ 8 : fffffffd 0000fc00 8052da00 00000000
[ 371.591212] $12 : 000b2285 ae53a1a9 00108845 89da44c4
[ 371.596615] $16 : 82edaad0 82ed9d20 00001798 832edf00
[ 371.602019] $20 : 00000000 8386dda8 80530000 fffffffe
[ 371.607421] $24 : 8051d040 76274d1b
[ 371.612824] $28 : 8386c000 8386dd88 82edaad4 830d4d50
[ 371.618228] Hi : 000000f7
[ 371.621203] Lo : 33333371
[ 371.624196] epc : 8042fbb0 __mutex_lock.isra.2+0x134/0x378
[ 371.630043] ra : 830d4d50 mt76u_deinit+0x418/0xa6c [mt76_usb]
[ 371.636237] Status: 1000fc03KERNEL EXL IE
[ 371.640557] Cause : 0080000c (ExcCode 03)
[ 371.644696] BadVA : 00000000
[ 371.647671] PrId : 00019374 (MIPS 24Kc)
[ 371.726123] usbcore nls_base usb_common
[ 371.730180] Process kworker/u2:2 (pid: 11, threadinfo=8386c000, task=83823ac0, tls=00000000)
[ 371.738884] Stack : 833d009c 83210b4c 82ed8bc0 8386ddac 000001ff 8008ac50 8386ddac 83b74b00
[ 371.747519] 82edaad4 00000000 83b74b48 83210c38 82edaad0 82ed9d20 00001798 832edf00
[ 371.756157] 00000000 00000000 80530000 fffffffe 80530000 830d4d50 00000040 8389d850
[ 371.764794] 8052d9d8 8389d850 8386de30 82ed9d20 8386de5f 831c27bc 833d48ec 8052d9d8
[ 371.773431] 83823ac0 83823af0 82edab00 82ed9d20 8386de5f 831c5c30 00000000 8052d9a8
[ 371.782069] ...
[ 371.784598] Call Trace:
[ 371.787130] [<8042fbb0>] __mutex_lock.isra.2+0x134/0x378
[ 371.792622] [<830d4d50>] mt76u_deinit+0x418/0xa6c [mt76_usb]
[ 371.808546]
[ 371.810920] ---[ end trace c62f0601f6730eb0 ]---
[ 371.818101] Kernel panic - not syncing: Fatal exception
[ 371.824420] Rebooting in 3 seconds..
Fix the issue relying only on data buffer to send/receive usb control messages
Fixes: a6bfb6d13f33 ("mt76: usb: use max packet length for m76u_copy")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.