On Wed, Nov 11, 2020 at 03:57:50PM +0100, Dmitry Vyukov wrote: > On Mon, Nov 2, 2020 at 12:54 PM syzbot > <syzbot+d29e58bb557324e55e5e@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > > > Hello, > > > > syzbot found the following issue on: > > > > HEAD commit: 080b6f40 bpf: Don't rely on GCC __attribute__((optimize)) .. > > git tree: bpf > > console output: https://syzkaller.appspot.com/x/log.txt?x=1089d37c500000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=58a4ca757d776bfe > > dashboard link: https://syzkaller.appspot.com/bug?extid=d29e58bb557324e55e5e > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10f4b032500000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1371a47c500000 > > > > The issue was bisected to: > > > > commit 9df1c28bb75217b244257152ab7d788bb2a386d0 > > Author: Matt Mullins <mmullins@xxxxxx> > > Date: Fri Apr 26 18:49:47 2019 +0000 > > > > bpf: add writable context for raw tracepoints > > > We have a number of kernel memory corruptions related to bpf_trace_run now: > https://groups.google.com/g/syzkaller-bugs/search?q=kernel%2Ftrace%2Fbpf_trace.c > > Can raw tracepoints "legally" corrupt kernel memory (a-la /dev/kmem)? > Or they shouldn't? > > Looking at the description of Matt's commit, it seems that corruptions > should not be possible (bounded buffer, checked size, etc). Then it > means it's a real kernel bug? This bug doesn't seem to be related to the writability of the tracepoint; it bisected to that commit simply because it used BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE for the reproducer and it EINVAL's before that program type was introduced. The BPF program it loads is pretty much a no-op. The problem here is a kmalloc failure injection into tracepoint_probe_unregister, but the error is ignored -- so the bpf program is freed even though the tracepoint is never unregistered. I have a first pass at a patch to pipe through the error code, but it's pretty ugly. It's also called from the file_operations ->release(), for which errors are solidly ignored in __fput(), so I'm not sure what the best way to handle ENOMEM is... > > > > > bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=12b6c4da500000 > > final oops: https://syzkaller.appspot.com/x/report.txt?x=11b6c4da500000 > > console output: https://syzkaller.appspot.com/x/log.txt?x=16b6c4da500000 > > > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > > Reported-by: syzbot+d29e58bb557324e55e5e@xxxxxxxxxxxxxxxxxxxxxxxxx > > Fixes: 9df1c28bb752 ("bpf: add writable context for raw tracepoints") > > > > ================================================================== > > BUG: KASAN: vmalloc-out-of-bounds in __bpf_trace_run kernel/trace/bpf_trace.c:2045 [inline] > > BUG: KASAN: vmalloc-out-of-bounds in bpf_trace_run3+0x3e0/0x3f0 kernel/trace/bpf_trace.c:2083 > > Read of size 8 at addr ffffc90000e6c030 by task kworker/0:3/3754 > > > > CPU: 0 PID: 3754 Comm: kworker/0:3 Not tainted 5.9.0-syzkaller #0 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > > Workqueue: 0x0 (events) > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x107/0x163 lib/dump_stack.c:118 > > print_address_description.constprop.0.cold+0x5/0x4c8 mm/kasan/report.c:385 > > __kasan_report mm/kasan/report.c:545 [inline] > > kasan_report.cold+0x1f/0x37 mm/kasan/report.c:562 > > __bpf_trace_run kernel/trace/bpf_trace.c:2045 [inline] > > bpf_trace_run3+0x3e0/0x3f0 kernel/trace/bpf_trace.c:2083 > > __bpf_trace_sched_switch+0xdc/0x120 include/trace/events/sched.h:138 > > __traceiter_sched_switch+0x64/0xb0 include/trace/events/sched.h:138 > > trace_sched_switch include/trace/events/sched.h:138 [inline] > > __schedule+0xeb8/0x2130 kernel/sched/core.c:4520 > > schedule+0xcf/0x270 kernel/sched/core.c:4601 > > worker_thread+0x14c/0x1120 kernel/workqueue.c:2439 > > kthread+0x3af/0x4a0 kernel/kthread.c:292 > > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 > > > > > > Memory state around the buggy address: > > ffffc90000e6bf00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 > > ffffc90000e6bf80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 > > >ffffc90000e6c000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 > > ^ > > ffffc90000e6c080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 > > ffffc90000e6c100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 > > ================================================================== > > > > > > --- > > This report is generated by a bot. It may contain errors. > > See https://goo.gl/tpsmEJ for more information about syzbot. > > syzbot engineers can be reached at syzkaller@xxxxxxxxxxxxxxxx. > > > > syzbot will keep track of this issue. See: > > https://goo.gl/tpsmEJ#status for how to communicate with syzbot. > > For information about bisection process see: https://goo.gl/tpsmEJ#bisection > > syzbot can test patches for this issue, for details see: > > https://goo.gl/tpsmEJ#testing-patches > > > > -- > > 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/00000000000004500b05b31e68ce%40google.com.
