On Tue, Sep 15, 2020 at 06:27:25AM +0200, Dmitry Vyukov wrote: > On Mon, Sep 14, 2020 at 6:51 PM Josh Poimboeuf <jpoim...@redhat.com> wrote: > > > > On Tue, Sep 08 2020 at 13:16, syzbot wrote: > > > > > > > > > Hello, > > > > > > > > > > syzbot found the following issue on: > > > > > > > > > > HEAD commit: f4d51dff Linux 5.9-rc4 > > > > > git tree: upstream > > > > > console output: > > > > > https://syzkaller.appspot.com/x/log.txt?x=1455d4f9900000 > > > > > kernel config: > > > > > https://syzkaller.appspot.com/x/.config?x=a9075b36a6ae26c9 > > > > > dashboard link: > > > > > https://syzkaller.appspot.com/bug?extid=bc9dbf05dcc151e9b972 > > > > > compiler: gcc (GCC) 10.1.0-syz 20200507 > > > > > > > > > > Unfortunately, I don't have any reproducer for this issue yet. > > > > > > > > > > IMPORTANT: if you fix the issue, please add the following tag to the > > > > > commit: > > > > > Reported-by: syzbot+bc9dbf05dcc151e9b...@syzkaller.appspotmail.com > > > > > > > > > > WARNING: can't access registers at > > > > > asm_sysvec_call_function_single+0x12/0x20 > > > > > arch/x86/include/asm/idtentry.h:589 > > > > > > > > That's the ORC unwinder complaining, but I have no idea why... > > > > > > 0000000000000cd0 <asm_sysvec_call_function_single>: > > > cd0: 90 nop > > > cd1: 90 nop > > > cd2: 90 nop > > > cd3: 6a ff pushq $0xffffffffffffffff > > > cd5: e8 b6 03 00 00 callq 1090 <error_entry> > > > cda: 48 89 e7 mov %rsp,%rdi > > > cdd: e8 00 00 00 00 callq ce2 > > > <asm_sysvec_call_function_single+0x12> > > > cde: R_X86_64_PLT32 > > > sysvec_call_function_single-0x4 > > > ce2: e9 69 04 00 00 jmpq 1150 <error_return> > > > ce7: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1) > > > cee: 00 00 > > > > > > This is a head scratcher. The ORC data looks ok, at least when I build > > > it on my system. It's expecting to find pt_regs at the top of the stack > > > after returning from sysvec_call_function_single(). But it can't > > > dereference the regs for some reason. > > > > > > So either it's a bug in ORC data or unwinder (not likely) or the stack > > > pointer got corrupted somehow (also seems unlikely)... > > > > The true bug may be revealed elsewhere on the stack... I probably need > > to start enabling ORC stack dumps like I did for FP. > > Hi Josh, > > Is there a config for this? We could enable it on syzbot. More > informative kernel diagnostics are always better.
Unfortunately the ORC dump code doesn't exist upstream yet. I need to dust the patches off and post. -- Josh
