Messages in this thread | | | Date | Thu, 14 Dec 2017 18:02:57 +0100 (CET) | From | Thomas Gleixner <> | Subject | Re: BUG: unable to handle kernel paging request in do_futex |
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On Thu, 14 Dec 2017, Andrey Ryabinin wrote: > On 12/14/2017 06:31 PM, Thomas Gleixner wrote: > > On Thu, 30 Nov 2017, syzbot wrote: > >> BUG: unable to handle kernel paging request at 00000000c314149f > > > > That's a user space address which is nowhere in the registers. Is that > > perhaps pre commit: 328b4ed93b69a ? > > Seems so. Kernel version is 4.15.0-rc1-next-20171130+ it shouldn't have that commit. > > >> IP: arch_futex_atomic_op_inuser arch/x86/include/asm/futex.h:67 [inline] > >> IP: futex_atomic_op_inuser kernel/futex.c:1588 [inline] > >> IP: futex_wake_op kernel/futex.c:1637 [inline] > >> IP: do_futex+0x14c8/0x2280 kernel/futex.c:3483 > >> PGD 5e28067 P4D 5e28067 PUD 5e2a067 PMD 0 > >> Oops: 0002 [#1] SMP KASAN > > > > ^^^^ X86_PF_WRITE > > > >> Dumping ftrace buffer: > >> (ftrace buffer empty) > >> Modules linked in: > >> CPU: 0 PID: 14626 Comm: syz-executor6 Not tainted 4.15.0-rc1-next-20171130+ > >> #56 > >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google > >> 01/01/2011 > >> task: 000000005f17dad6 task.stack: 000000005af7607c > >> RIP: 0010:arch_futex_atomic_op_inuser arch/x86/include/asm/futex.h:67 [inline] > >> RIP: 0010:futex_atomic_op_inuser kernel/futex.c:1588 [inline] > >> RIP: 0010:futex_wake_op kernel/futex.c:1637 [inline] > >> RIP: 0010:do_futex+0x14c8/0x2280 kernel/futex.c:3483 > >> RSP: 0018:ffff8801cffafa18 EFLAGS: 00010246 > >> RAX: 000000007fffffff RBX: 0000000040000002 RCX: ffffffff8164e3d9 > >> RDX: 0000000000000000 RSI: ffffc900034e8000 RDI: 0000000000000000 > >> RBP: ffff8801cffafe38 R08: 1ffffffff0d31367 R09: 0000000000000004 > >> R10: 0000000000000000 R11: ffffffff8748cd60 R12: ffff8801d0f30180 > >> R13: 0000000020000000 R14: dffffc0000000000 R15: ffff8801cffafe10 > >> FS: 00007f66305e0700(0000) GS:ffff8801db400000(0000) knlGS:0000000000000000 > >> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > >> CR2: fffffffffffffff8 CR3: 00000001ccc2e000 CR4: 00000000001426f0 > > > > ^^^^^^^^^^^^^^^^ is a totally different address so its either > > completely bogus or the above address is a hashed pointer because > > that printk used to be %p and was changed to %px in 328b4ed93b69a > > > >> DR0: 0000000020000000 DR1: 0000000020000000 DR2: 0000000000000000 > >> DR3: 0000000000000000 DR6: 00000000ffff0ff3 DR7: 0000000000bb060a > >> Call Trace: > >> SYSC_futex kernel/futex.c:3533 [inline] > >> SyS_futex+0x260/0x390 kernel/futex.c:3501 > >> entry_SYSCALL_64_fastpath+0x1f/0x96 > >> RIP: 0033:0x4529d9 > >> RSP: 002b:00007f66305dfc58 EFLAGS: 00000212 ORIG_RAX: 00000000000000ca > >> RAX: ffffffffffffffda RBX: 00007f66305e0700 RCX: 00000000004529d9 > >> RDX: 0000000000000007 RSI: 0000000000000085 RDI: 0000000020062000 > >> RBP: 0000000000000000 R08: 0000000020000000 R09: 0000000040000002 > >> R10: 000000002085fff0 R11: 0000000000000212 R12: 0000000000000000 > >> R13: 0000000000a6f7ff R14: 00007f66305e09c0 R15: 0000000000000000 > > > > The arguments are: > > > > RDI uaddr 0000000020062000 > > RSI op 0000000000000085 > > RDX val 0000000000000007 > > RCX utime 00000000004529d9 > > R8 uaddr2 0000000020000000 > > R9 val2 0000000040000002 > > > >> Code: 31 d2 0f 1f 00 45 87 65 00 0f 1f 00 89 95 30 fc ff ff e9 1d ff ff ff e8 > >> 67 56 0b 00 31 d2 8b bd 00 fc ff ff 0f 1f 00 41 8b 45 00 <89> c1 31 f9 f0 41 > >> 0f b1 4d 00 75 f0 0f 1f 00 41 89 c4 89 95 30 > > > > and the code is: > > > > 27: 41 8b 45 00 mov 0x0(%r13),%eax > > 2b:* 89 c1 mov %eax,%ecx <-- trapping instruction > > 2d: 31 f9 xor %edi,%ecx > > 2f: f0 41 0f b1 4d 00 lock cmpxchg %ecx,0x0(%r13) > > 35: 75 f0 jne 0x27 > > > > The trapping instruction cannot trap :). Assumed it's the move before that, > > then the accessed location is R13 + 0 = 0000000020000000, which is uaddr2 > > and entirely correct. > > > But fault address must be 0xfffffffffffffff8 as per CR2, so it can't be > 'mov 0x0(%r13),%eax' either. Right?
Indeed
> > And what I completely fail to understand why this triggers at all. That > > code section is guarded by an extable fixup so this should never come in. > > > > Is this a KASAN artifact? > > > I don't see any evidence for KASAN being involved here.
I was just asking because of:
>> Oops: 0002 [#1] SMP KASAN
Thanks,
tglx
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