On Fri, Sep 7, 2018 at 9:17 AM, Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > On 2018/09/08 0:29, syzbot wrote: >> syzbot has found a reproducer for the following crash on: >> >> HEAD commit: 28619527b8a7 Merge git://git.kernel.org/pub/scm/linux/kern.. >> git tree: bpf >> console output: https://syzkaller.appspot.com/x/log.txt?x=124e64d1400000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=62e9b447c16085cf >> dashboard link: https://syzkaller.appspot.com/bug?extid=a3c9d2673837ccc0f22b >> compiler: gcc (GCC) 8.0.1 20180413 (experimental) >> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179f9cd1400000 >> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11b3e8be400000 >> >> IMPORTANT: if you fix the bug, please add the following tag to the commit: >> Reported-by: syzbot+a3c9d2673837ccc0f22b@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> entry_SYSCALL_64_after_hwframe+0x49/0xbe >> RIP: 0033:0x440479 >> usercopy: Kernel memory overwrite attempt detected to spans multiple pages (offset 0, size 64)! > > Kees, is this because check_page_span() is failing to allow on-stack variable > > u8 opcodes[OPCODE_BUFSIZE]; > > which by chance crossed PAGE_SIZE boundary? There are a lot of failure conditions for the PAGESPAN check. This might be one (and one that I'm hoping to solve separately). -Kees -- Kees Cook Pixel Security
