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 > @@ -1875,16 +1877,20 @@ static ssize_t fuse_dev_do_write(struct fuse_dev *fud, > > /* Is it an interrupt reply? */ > if (req->intr_unique == oh.unique) { > + __fuse_get_request(req); > spin_unlock(&fpq->lock); > > err = -EINVAL; > - if (nbytes != sizeof(struct fuse_out_header)) > + if (nbytes != sizeof(struct fuse_out_header)) { > + fuse_put_request(fc, req); > goto err_finish; > + } > > if (oh.error == -ENOSYS) > fc->no_interrupt = 1; > else if (oh.error == -EAGAIN) > queue_interrupt(&fc->iq, req); > + fuse_put_request(fc, req); > > fuse_copy_finish(cs); > return nbytes; > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/274aafd2-5076-6b14-f55e-360411fb8169%40virtuozzo.com. > For more options, visit https://groups.google.com/d/optout.
