Dear All,
On 19.01.2024 10:48, Uttkarsh Aggarwal wrote:
In current scenario if Plug-out and Plug-In performed continuously there could be a chance while checking for dwc->gadget_driver in dwc3_gadget_suspend, a NULL pointer dereference may occur.
Call Stack:
CPU1: CPU2: gadget_unbind_driver dwc3_suspend_common dwc3_gadget_stop dwc3_gadget_suspend dwc3_disconnect_gadget
CPU1 basically clears the variable and CPU2 checks the variable. Consider CPU1 is running and right before gadget_driver is cleared and in parallel CPU2 executes dwc3_gadget_suspend where it finds dwc->gadget_driver which is not NULL and resumes execution and then CPU1 completes execution. CPU2 executes dwc3_disconnect_gadget where it checks dwc->gadget_driver is already NULL because of which the NULL pointer deference occur.
Cc: stable@vger.kernel.org Fixes: 9772b47a4c29 ("usb: dwc3: gadget: Fix suspend/resume during device mode") Acked-by: Thinh Nguyen Thinh.Nguyen@synopsys.com Signed-off-by: Uttkarsh Aggarwal quic_uaggarwa@quicinc.com
This patch landed some time ago in linux-next as commit 61a348857e86 ("usb: dwc3: gadget: Fix NULL pointer dereference in dwc3_gadget_suspend"). Recently I found that it causes the following warning when no USB gadget is bound to the DWC3 driver and a system suspend/resume cycle is performed:
dwc3 12400000.usb: wait for SETUP phase timed out dwc3 12400000.usb: failed to set STALL on ep0out ------------[ cut here ]------------ WARNING: CPU: 4 PID: 604 at drivers/usb/dwc3/ep0.c:289 dwc3_ep0_out_start+0xc8/0xcc Modules linked in: CPU: 4 PID: 604 Comm: rtcwake Not tainted 6.8.0-rc3-next-20240207 #7979 Hardware name: Samsung Exynos (Flattened Device Tree) unwind_backtrace from show_stack+0x10/0x14 show_stack from dump_stack_lvl+0x58/0x70 dump_stack_lvl from __warn+0x7c/0x1bc __warn from warn_slowpath_fmt+0x1a0/0x1a8 warn_slowpath_fmt from dwc3_ep0_out_start+0xc8/0xcc dwc3_ep0_out_start from dwc3_gadget_soft_disconnect+0x16c/0x230 dwc3_gadget_soft_disconnect from dwc3_gadget_suspend+0xc/0x90 dwc3_gadget_suspend from dwc3_suspend_common+0x44/0x30c dwc3_suspend_common from dwc3_suspend+0x14/0x2c dwc3_suspend from dpm_run_callback+0x94/0x288 dpm_run_callback from device_suspend+0x130/0x6d0 device_suspend from dpm_suspend+0x124/0x35c dpm_suspend from dpm_suspend_start+0x64/0x6c dpm_suspend_start from suspend_devices_and_enter+0x134/0xbd8 suspend_devices_and_enter from pm_suspend+0x2ec/0x380 pm_suspend from state_store+0x68/0xc8 state_store from kernfs_fop_write_iter+0x110/0x1d4 kernfs_fop_write_iter from vfs_write+0x2e8/0x430 vfs_write from ksys_write+0x5c/0xd4 ksys_write from ret_fast_syscall+0x0/0x1c Exception stack(0xf1421fa8 to 0xf1421ff0) ... irq event stamp: 14304 hardirqs last enabled at (14303): [<c01a599c>] console_unlock+0x108/0x114 hardirqs last disabled at (14304): [<c0c229d8>] _raw_spin_lock_irqsave+0x64/0x68 softirqs last enabled at (13030): [<c010163c>] __do_softirq+0x318/0x4f4 softirqs last disabled at (13025): [<c012dd40>] __irq_exit_rcu+0x130/0x184 ---[ end trace 0000000000000000 ]---
IMHO dwc3_gadget_soft_disconnect() requires some kind of a check if dwc->gadget_driver is present or not, as it really makes no sense to do any ep0 related operations if there is no gadget driver at all.
changes in v3: Corrected fixes tag and typo mistake in commit message dw3_gadget_stop -> dwc3_gadget_stop.
Link to v2: https://lore.kernel.org/linux-usb/CAKzKK0r8RUqgXy1o5dndU21KuTKtyZ5rn5Fb9sZqT...
Changes in v2: Added cc and fixes tag missing in v1.
Link to v1: https://lore.kernel.org/linux-usb/20240110095532.4776-1-quic_uaggarwa@quicin...
drivers/usb/dwc3/gadget.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 019368f8e9c4..564976b3e2b9 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -4709,15 +4709,13 @@ int dwc3_gadget_suspend(struct dwc3 *dwc) unsigned long flags; int ret;
- if (!dwc->gadget_driver)
return 0;- ret = dwc3_gadget_soft_disconnect(dwc); if (ret) goto err;
spin_lock_irqsave(&dwc->lock, flags);
- dwc3_disconnect_gadget(dwc);
- if (dwc->gadget_driver)
dwc3_disconnect_gadget(dwc);return 0;
Best regards