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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20210315174425.2201225-1-jordy@pwning.systems> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15/03/2021 17:44, Jordy Zomer wrote: > My syzkaller instance reported a use-after-free bug in io_wqe_inc_running. > I tried fixing this by checking if wq isn't NULL in io_wqe_worker. > If it does; return an -EFAULT. This because create_io_worker() will clean-up the worker if there's an error. > > If you want I could send you the syzkaller reproducer and crash-logs :) Yes, please. Haven't looked up properly, but looks that wq==NULL should never happen, so the fix is a bit racy. > > Best Regards, > > Jordy Zomer > > Signed-off-by: Jordy Zomer > --- > fs/io-wq.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/io-wq.c b/fs/io-wq.c > index 0ae9ecadf295..9ed92d88a088 100644 > --- a/fs/io-wq.c > +++ b/fs/io-wq.c > @@ -482,6 +482,10 @@ static int io_wqe_worker(void *data) > char buf[TASK_COMM_LEN]; > > worker->flags |= (IO_WORKER_F_UP | IO_WORKER_F_RUNNING); > + > + if (wq == NULL) > + return -EFAULT; > + > io_wqe_inc_running(worker); > > sprintf(buf, "iou-wrk-%d", wq->task_pid); > -- Pavel Begunkov