On Sun, Sep 13, 2020 at 11:05:21PM +0200, Thomas Gleixner 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: [email protected]
> >
> > 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)...
--
Josh
