On Mon, Jan 22, 2024 at 6:12 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > On Mon, Jan 22, 2024 at 05:30:18PM +0100, Eric Dumazet wrote: > > On Mon, Jan 22, 2024 at 5:04 PM Matthew Wilcox <willy@xxxxxxxxxxxxx> wrote: > > > I'm disappointed to have no reaction from netdev so far. Let's see if a > > > more exciting subject line evinces some interest. > > > > Hmm, perhaps some of us were enjoying their weekend ? > > I am all in favour of people taking time off! However the report came > in on Friday at 9am UTC so it had been more than a work day for anyone > anywhere in the world without response. > > > I don't really know what changed recently, all I know is that TCP zero > > copy is for real network traffic. > > > > Real trafic uses order-0 pages, 4K at a time. > > > > If can_map_frag() needs to add another safety check, let's add it. > > So it's your opinion that people don't actually use sendfile() from > a local file, and we can make this fail to zerocopy? Certainly we do not do that at Google. I am not sure if anybody else would have used this. That's good > because I had a slew of questions about what expectations we had around > cache coherency between pages mapped this way and write()/mmap() of > the original file. If we can just disallow this, we don't need to > have a discussion about it. > > > syzbot is usually quite good at bisections, was a bug origin found ? > > I have the impression that Huawei run syzkaller themselves without > syzbot. I suspect this bug has been there for a good long time. > Wonder why nobody's found it before; it doesn't seem complicated for a > fuzzer to stumble into. I is strange syzbot (The Google fuzzer) have not found this yet, I suspect it might be caused by a recent change somewhere ? A repro would definitely help, I could start a bisection.
