On 25.09.2018 12:38, Dmitry Vyukov wrote: > On Tue, Sep 25, 2018 at 11:18 AM, Kirill Tkhai <ktkhai@xxxxxxxxxxxxx> wrote: >> On 24.09.2018 17:44, Miklos Szeredi wrote: >>> On Mon, Sep 24, 2018 at 2:29 PM, syzbot >>> <syzbot+ef054c4d3f64cd7f7cec@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: >>>> Hello, >>>> >>>> syzbot found the following crash on: >>>> >>>> HEAD commit: 6bf4ca7fbc85 Linux 4.19-rc5 >>>> git tree: upstream >>>> console output: https://syzkaller.appspot.com/x/log.txt?x=159149c6400000 >>>> kernel config: https://syzkaller.appspot.com/x/.config?x=22a62640793a83c9 >>>> dashboard link: https://syzkaller.appspot.com/bug?extid=ef054c4d3f64cd7f7cec >>>> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >>>> >>>> Unfortunately, I don't have any reproducer for this crash yet. >>>> >>>> IMPORTANT: if you fix the bug, please add the following tag to the commit: >>>> Reported-by: syzbot+ef054c4d3f64cd7f7cec@xxxxxxxxxxxxxxxxxxxxxxxxx >>>> >>>> WARNING: CPU: 0 PID: 9445 at fs/fuse/dev.c:390 request_end+0x82e/0xaa0 >>> >>> And there we have the bug likely caused by the set_bit(FR_SENT, ...) >>> not being inside the fpq->lock-ed region. >>> >>> So that needs to be fixed anyway, apparently. >> >> I can't confirm, since I haven't found yet the direct way, that set_bit() results >> in this stack... >> >> We have one more (unrelated) possible use-after-free here: >> >> cpu0 cpu1 >> fuse_dev_do_write() fuse_dev_do_write() >> req = request_find(fpq, oh.unique) ... >> spin_unlock(&fpq->lock) ... >> ... req = request_find(fpq, oh.unique) >> ... spin_unlock(&fpq->lock) >> queue_interrupt(&fc->iq, req); ... >> ... ... >> ... ... >> request freed ... >> ... queue_interrupt(&fc->iq, req); <- use after free >> >> Something like below is needed: > > There is a bunch of open bugs in fuse on syzbot dashboard, perhaps > it's one of them: > > https://syzkaller.appspot.com/bug?id=19aabec97cbf73dd0475d6e599113a7861c4b306 > https://syzkaller.appspot.com/bug?id=24aa489e6929205e40ec4aa52cd8f47897f2ad63 > https://syzkaller.appspot.com/bug?id=400d6a977a0dbd8836d7c7ec8481782a674ee855 > https://syzkaller.appspot.com/bug?id=ff9ab4a23afa7553fb79f745a92be87ba4144508 > https://syzkaller.appspot.com/bug?id=d0f258de27b6d7ccecbba09385b3376cc4a12ffe > https://syzkaller.appspot.com/bug?id=e8077bce636d52d9c40e1ea904699c27b7454354 I can't find fuse_dev_do_write() there, but it's possible this race could appear in another function. So, Dmitry, I won't add reference to one of tham. Let's check, which will disappear in the future. Thanks, Kirill
