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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Proofpoint-ORIG-GUID: 3bzjiwD_4oySEvEA5BrKr_oPr9Exjxzu X-Authority-Analysis: v=2.4 cv=edY9f6EH c=1 sm=1 tr=0 ts=6852b075 cx=c_pps a=MTSHoo12Qbhz2p7MsH1ifg==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=6IFa9wvqVegA:10 a=VwQbUJbxAAAA:8 a=1XWaLZrsAAAA:8 a=EUspDBNiAAAA:8 a=MIvUBlGXxtpg5XUkedoA:9 a=QEXdDO2ut3YA:10 a=GvdueXVYPmCkWapjIL-Q:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwNjE4MDEwNCBTYWx0ZWRfX3syFB0a/JDvL ql2imctEfH+bUIn80kZcJ3pQD+SYo8RI32uewOy4RBRx+h8H8RrQ5DcQjs3HXdfLUaAhybtOBEE adSbUqTC+xfp/NWCHZEi7VKGGY0K2ciYn5lsr/ZSP3f0ePuZYTEgucSf4maifCs9ZYm4QEcO0aq gsJ1At/eYKoWizqgc1BK9+LLQ9QGfBAOepogmURiK/GcAVi6RJwsWZ56N8Qqt6gaPknvzNcOpdU Clcl26TzFmnTCq98vEE1rpLhwnUXxUniDp8AQ2rYwL4bE/wStKjlcp0c8aykX7pL8JZ2t2R0VZ+ SEcqwrV2W6lIReVTFhVRN2A0r0sZBGRI/RApZ5oHxOXUEFX3SoADd+oz9VDnMzkGm7JTCUmk3/o 7OFKNzyg9CuQ1vuQ6+iktYvwBpXf69jSpADhWEsATM/sq9bBhdFZKE+ivS5aUv7Ir+RmFjaJ X-Proofpoint-GUID: 3bzjiwD_4oySEvEA5BrKr_oPr9Exjxzu X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.0.736,FMLib:17.12.80.40 definitions=2025-06-18_05,2025-06-18_02,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 spamscore=0 bulkscore=0 impostorscore=0 mlxscore=0 clxscore=1015 mlxlogscore=825 malwarescore=0 phishscore=0 adultscore=0 classifier=spam authscore=0 authtc=n/a authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2505280000 definitions=main-2506180104 On 6/17/2025 10:37 AM, Kuen-Han Tsai wrote: > A race condition occurs when gs_start_io() calls either gs_start_rx() or > gs_start_tx(), as those functions briefly drop the port_lock for > usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear > port.tty and port_usb, respectively. > > Use the null-safe TTY Port helper function to wake up TTY. > > Example > CPU1: CPU2: > gserial_connect() // lock > gs_close() // await lock > gs_start_rx() // unlock > usb_ep_queue() > gs_close() // lock, reset port.tty and unlock > gs_start_rx() // lock > tty_wakeup() // NPE > > Fixes: 35f95fd7f234 ("TTY: usb/u_serial, use tty from tty_port") > Cc: stable@vger.kernel.org > Signed-off-by: Kuen-Han Tsai > --- Reviewed-by: Prashanth K > v2: > - Move the example up to the changelog > > Traces: > [ 51.494375][ T278] ttyGS1: shutdown > [ 51.494817][ T269] android_work: sent uevent USB_STATE=DISCONNECTED > [ 52.115792][ T1508] usb: [dm_bind] generic ttyGS1: super speed IN/ep1in OUT/ep1out > [ 52.516288][ T1026] android_work: sent uevent USB_STATE=CONNECTED > [ 52.551667][ T1533] gserial_connect: start ttyGS1 > [ 52.565634][ T1533] [khtsai] enter gs_start_io, ttyGS1, port->port.tty=0000000046bd4060 > [ 52.565671][ T1533] [khtsai] gs_start_rx, unlock port ttyGS1 > [ 52.591552][ T1533] [khtsai] gs_start_rx, lock port ttyGS1 > [ 52.619901][ T1533] [khtsai] gs_start_rx, unlock port ttyGS1 > [ 52.638659][ T1325] [khtsai] gs_close, lock port ttyGS1 > [ 52.656842][ T1325] gs_close: ttyGS1 (0000000046bd4060,00000000be9750a5) ... > [ 52.683005][ T1325] [khtsai] gs_close, clear ttyGS1 > [ 52.683007][ T1325] gs_close: ttyGS1 (0000000046bd4060,00000000be9750a5) done! > [ 52.708643][ T1325] [khtsai] gs_close, unlock port ttyGS1 > [ 52.747592][ T1533] [khtsai] gs_start_rx, lock port ttyGS1 > [ 52.747616][ T1533] [khtsai] gs_start_io, ttyGS1, going to call tty_wakeup(), port->port.tty=0000000000000000 > [ 52.747629][ T1533] Unable to handle kernel NULL pointer dereference at virtual address 00000000000001f8 > --- > drivers/usb/gadget/function/u_serial.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c > index c043bdc30d8a..540dc5ab96fc 100644 > --- a/drivers/usb/gadget/function/u_serial.c > +++ b/drivers/usb/gadget/function/u_serial.c > @@ -295,8 +295,8 @@ __acquires(&port->port_lock) > break; > } > > - if (do_tty_wake && port->port.tty) > - tty_wakeup(port->port.tty); > + if (do_tty_wake) > + tty_port_tty_wakeup(&port->port); > return status; > } > > @@ -574,7 +574,7 @@ static int gs_start_io(struct gs_port *port) > gs_start_tx(port); > /* Unblock any pending writes into our circular buffer, in case > * we didn't in gs_start_tx() */ > - tty_wakeup(port->port.tty); Just curious, since this is already under lock, checking for port->port.tty would have also helped, right? Anyways looks like tty_port_tty_wakeup is better. > + tty_port_tty_wakeup(&port->port); > } else { > /* Free reqs only if we are still connected */ > if (port->port_usb) { > -- > 2.50.0.rc2.692.g299adb8693-goog >