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Commita7f3813e58("usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler") switched dummy_hcd to use hrtimer and made the timer's callback be executed in the hardirq context. With that change, __usb_hcd_giveback_urb now gets executed in the hardirq context, which causes problems for KCOV and KMSAN. One problem is that KCOV now is unable to collect coverage from the USB code that gets executed from the dummy_hcd's timer callback, as KCOV cannot collect coverage in the hardirq context. Another problem is that the dummy_hcd hrtimer might get triggered in the middle of a softirq with KCOV remote coverage collection enabled, and that causes a WARNING in KCOV, as reported by syzbot. (I sent a separate patch to shut down this WARNING, but that doesn't fix the other two issues.) Finally, KMSAN appears to ignore tracking memory copying operations that happen in the hardirq context, which causes false positive kernel-infoleaks, as reported by syzbot. Change the hrtimer in dummy_hcd to execute the callback in the softirq context. Reported-by: syzbot+2388cdaeb6b10f0c13ac@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=2388cdaeb6b10f0c13ac Reported-by: syzbot+17ca2339e34a1d863aad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=17ca2339e34a1d863aad Reported-by: syzbot+c793a7eca38803212c61@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c793a7eca38803212c61 Reported-by: syzbot+1e6e0b916b211bee1bd6@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1e6e0b916b211bee1bd6 Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202406141323.413a90d2-lkp@intel.com Fixes:a7f3813e58("usb: gadget: dummy_hcd: Switch to hrtimer transfer scheduler") Cc: stable@vger.kernel.org Acked-by: Marcello Sylvester Bauer <sylv@sylv.io> Signed-off-by: Andrey Konovalov <andreyknvl@gmail.com> Reported-by: syzbot+edd9fe0d3a65b14588d5@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=edd9fe0d3a65b14588d5 Link: https://lore.kernel.org/r/20240904013051.4409-1-andrey.konovalov@linux.dev Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 reStructuredText 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.