On Thu, Jan 11, 2024 at 6:58 PM David Hildenbrand <david@xxxxxxxxxx> wrote: > > On 11.01.24 19:34, Suren Baghdasaryan wrote: > > On Thu, Jan 11, 2024 at 8:44 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > >> > >> On Thu, Jan 11, 2024 at 8:40 AM Suren Baghdasaryan <surenb@xxxxxxxxxx> wrote: > >>> > >>> On Thu, Jan 11, 2024 at 8:25 AM syzbot > >>> <syzbot+705209281e36404998f6@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > >>>> > >>>> Hello, > >>>> > >>>> syzbot found the following issue on: > >>>> > >>>> HEAD commit: e2425464bc87 Add linux-next specific files for 20240105 > >>>> git tree: linux-next > >>>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=14941cdee80000 > >>>> kernel config: https://syzkaller.appspot.com/x/.config?x=4056b9349f3da8c9 > >>>> dashboard link: https://syzkaller.appspot.com/bug?extid=705209281e36404998f6 > >>>> compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 > >>>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=125d0a09e80000 > >>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15bc7331e80000 > >>>> > >>>> Downloadable assets: > >>>> disk image: https://storage.googleapis.com/syzbot-assets/2f738185e2cf/disk-e2425464.raw.xz > >>>> vmlinux: https://storage.googleapis.com/syzbot-assets/b248fcf4ea46/vmlinux-e2425464.xz > >>>> kernel image: https://storage.googleapis.com/syzbot-assets/a9945c8223f4/bzImage-e2425464.xz > >>>> > >>>> The issue was bisected to: > >>>> > >>>> commit adef440691bab824e39c1b17382322d195e1fab0 > >>>> Author: Andrea Arcangeli <aarcange@xxxxxxxxxx> > >>>> Date: Wed Dec 6 10:36:56 2023 +0000 > >>>> > >>>> userfaultfd: UFFDIO_MOVE uABI > >>>> > >>>> bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=11cb6ea9e80000 > >>>> final oops: https://syzkaller.appspot.com/x/report.txt?x=13cb6ea9e80000 > >>>> console output: https://syzkaller.appspot.com/x/log.txt?x=15cb6ea9e80000 > >>>> > >>>> IMPORTANT: if you fix the issue, please add the following tag to the commit: > >>>> Reported-by: syzbot+705209281e36404998f6@xxxxxxxxxxxxxxxxxxxxxxxxx > >>>> Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") > >>>> > >>>> do_one_initcall+0x128/0x680 init/main.c:1237 > >>>> do_initcall_level init/main.c:1299 [inline] > >>>> do_initcalls init/main.c:1315 [inline] > >>>> do_basic_setup init/main.c:1334 [inline] > >>>> kernel_init_freeable+0x692/0xc30 init/main.c:1552 > >>>> kernel_init+0x1c/0x2a0 init/main.c:1442 > >>>> ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147 > >>>> ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242 > >>>> ------------[ cut here ]------------ > >>>> kernel BUG at include/linux/page-flags.h:1035! > >>>> invalid opcode: 0000 [#1] PREEMPT SMP KASAN > >>>> CPU: 0 PID: 5068 Comm: syz-executor191 Not tainted 6.7.0-rc8-next-20240105-syzkaller #0 > >>>> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023 > >>>> RIP: 0010:PageAnonExclusive include/linux/page-flags.h:1035 [inline] > >>> > >>> From a quick look, I think the new ioctl is being used against a > >>> file-backed page and that's why PageAnonExclusive() throws this error. > >>> I'll confirm if this is indeed the case and will add checks for that > >>> case. Thanks! > >> > >> Hmm. Looking at the reproducer it does not look like a file-backed > >> memory... Anyways, I'm on it. > > > > Looks like the test is trying to move the huge_zero_page. Wonder how > > we should handle this. Just fail or do something else? Adding David > > and Peter for feedback. > > You'll need some special-casing to handle that. But it should be fairly > easy. Ok, so should we treat zeropage the same as PAE and map destination PTE/PMD to zeropage while clearing source PTE/PMD? > > -- > Cheers, > > David / dhildenb >
