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62c73bfea0
dwc->desired_dr_role is changed by dwc3_set_mode inside a spinlock but
then read by __dwc3_set_mode outside of that lock. This can lead to a
race condition when very quick successive role switch events happen:
CPU A
dwc3_set_mode(DWC3_GCTL_PRTCAP_HOST) // first role switch event
spin_lock_irqsave(&dwc->lock, flags);
dwc->desired_dr_role = mode; // DWC3_GCTL_PRTCAP_HOST
spin_unlock_irqrestore(&dwc->lock, flags);
queue_work(system_freezable_wq, &dwc->drd_work);
CPU B
__dwc3_set_mode
// ....
spin_lock_irqsave(&dwc->lock, flags);
// desired_dr_role is DWC3_GCTL_PRTCAP_HOST
dwc3_set_prtcap(dwc, dwc->desired_dr_role);
spin_unlock_irqrestore(&dwc->lock, flags);
CPU A
dwc3_set_mode(DWC3_GCTL_PRTCAP_DEVICE) // second event
spin_lock_irqsave(&dwc->lock, flags);
dwc->desired_dr_role = mode; // DWC3_GCTL_PRTCAP_DEVICE
spin_unlock_irqrestore(&dwc->lock, flags);
CPU B (continues running __dwc3_set_mode)
switch (dwc->desired_dr_role) { // DWC3_GCTL_PRTCAP_DEVICE
// ....
case DWC3_GCTL_PRTCAP_DEVICE:
// ....
ret = dwc3_gadget_init(dwc);
We then have DWC3_GCTL.DWC3_GCTL_PRTCAPDIR = DWC3_GCTL_PRTCAP_HOST and
dwc->current_dr_role = DWC3_GCTL_PRTCAP_HOST but initialized the
controller in device mode. It's also possible to get into a state
where both host and device are intialized at the same time.
Fix this race by creating a local copy of desired_dr_role inside
__dwc3_set_mode while holding dwc->lock.
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
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.