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AJvYcCXB++81mrLr/tkDePqSBfjMvbWHAS7XsA3qaV9JHeot7j4whJwFpMa5dEOjAtB3IaCXJPD4tGxo8lRC5QfyZS/Dv5w= X-Gm-Message-State: AOJu0YwFfiotwoHu6jqNdOSGD6ilAhMim2KUhW3OwOmmdiCcSB86c8Dc 9vhK/KEJmHpt1Tz29Gggwyeh/6ErNBRHj0C6s+phlPKtX1GS6nu/NwFr67A4trI+cHxNRBQ9r3c NePArrSo2rqzSh4epk/hgSqinUs/ZTJecL6Ec X-Google-Smtp-Source: AGHT+IF+eJ/yOfT8He9fhZRxlhLxrCA8EO5BcB2j5C7/E9D5kNDpoCIVUp0J9rAlNwgnKL8gKHxSp+tNgJOpiG/gEwA= X-Received: by 2002:a05:6214:5c02:b0:6b5:8015:d72d with SMTP id 6a1803df08f44-6bd79b4b3f0mr27122676d6.8.1723216959717; Fri, 09 Aug 2024 08:22:39 -0700 (PDT) MIME-Version: 1.0 References: <20240729022316.92219-1-andrey.konovalov@linux.dev> In-Reply-To: <20240729022316.92219-1-andrey.konovalov@linux.dev> From: Alexander Potapenko Date: Fri, 9 Aug 2024 17:22:00 +0200 Message-ID: Subject: Re: [PATCH] usb: gadget: dummy_hcd: execute hrtimer callback in softirq context To: andrey.konovalov@linux.dev Cc: Alan Stern , Greg Kroah-Hartman , Marcello Sylvester Bauer , Andrey Konovalov , Dmitry Vyukov , Aleksandr Nogikh , Marco Elver , kasan-dev@googlegroups.com, Andrew Morton , linux-mm@kvack.org, linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+2388cdaeb6b10f0c13ac@syzkaller.appspotmail.com, syzbot+17ca2339e34a1d863aad@syzkaller.appspotmail.com, stable@vger.kernel.org, Jann Horn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E5C1B40013 X-Stat-Signature: zbfwtkx6a4peab7xsiu4ig17kfqkfhea X-HE-Tag: 1723216960-263750 X-HE-Meta: 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 Pku+RCGZ /lME9pKmqT7eMNRii5V0hrQYRElFRjKGjJZJ+FuYIio3NWw6QCnqU3DR/CTjWx8bq+10Dvpbo7xCdbwvBJGOf6ZNvT42t2CgYlzcXB488Vkn7d5WO+0JoPn1+uWEXgA8uDCTXIHMmPRWObAdwT0YdaJ1oLI6ELCjiVQcSWVB20UFTjY+TYQ2wDLib+TOVoX0dV/ZhlicAsZ3j/n7/+Teo4ZI0PciIOEB9QgP2zc1IScO0Y+kxvxqIexMgfrC6IX0EMOTcEOq2YxMzB6o+0nn6xQ/8zWd3blQaYc5dAxtS65Tjz+bDf9AZSecqBstCBp0xuy44rwGSxBqJelo9mzNvEhGKUtWRV+Pq0sOtubJGMr7yPtYxEN/Gb4U/jWGLO6aNcPbaUl9g3X3CRu8rX0DVYJNJOA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Jul 29, 2024 at 4:23=E2=80=AFAM wrote: > > From: Andrey Konovalov > > Commit a7f3813e589f ("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 tha= t > 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. Hi Andrey, FWIW this problem is tracked as https://github.com/google/kmsan/issues/92, I'll try to revisit it in September.