Messages in this thread | | | From | Dmitry Vyukov <> | Date | Tue, 19 Dec 2017 13:12:41 +0100 | Subject | Re: BUG: unable to handle kernel paging request in do_futex |
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On Thu, Dec 14, 2017 at 6:02 PM, Thomas Gleixner <tglx@linutronix.de> wrote: > 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
#syz dup: BUG: unable to handle kernel paging request in __switch_to
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