Messages in this thread | | | Date | Tue, 15 May 2018 23:48:25 +0900 | From | Masami Hiramatsu <> | Subject | Re: WARNING in arch_uprobe_analyze_insn |
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On Tue, 15 May 2018 15:36:30 +0200 Oleg Nesterov <oleg@redhat.com> wrote:
> On 05/14, syzbot wrote: > > > > Hello, > > > > syzbot found the following crash on: > > > > HEAD commit: 66e1c94db3cd Merge branch 'x86-pti-for-linus' of git://git.. > > git tree: upstream > > console output: https://syzkaller.appspot.com/x/log.txt?x=11817107800000 > > kernel config: https://syzkaller.appspot.com/x/.config?x=fcce42b221691ff9 > > dashboard link: https://syzkaller.appspot.com/bug?extid=30d675e3ca03c1c351e7 > > compiler: gcc (GCC) 8.0.1 20180413 (experimental) > > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=143d5417800000 > > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11178e97800000 > > doesn't work for me... > > I guess syscall(__NR_perf_event_open) should trigger perf_uprobe_init() but > the hard-coded attr.type doesn't match perf_uprobe->type on my machine... > > > Nevermind, it seems that the code is indeed wrong, uprobe_init_insn() does > > insn_init(insn, auprobe->insn, sizeof(auprobe->insn), x86_64); > /* has the side-effect of processing the entire instruction */ > insn_get_length(insn); > if (WARN_ON_ONCE(!insn_complete(insn))) > return -ENOEXEC; > > Masami, could your help? > > What if insn can't be decoded, say, because it is not valid? Can't > insn_complete() return F in this case?
Yes, as far as it failes to decode.
BTW, insn_complete() may not work some errors, it is hard to find all invalid combination of x86 insn. I think the uprobes is fundamentary week about fuzzing code because it can not identify the instruction boundary in user space.
> I think it can... Say, insn_get_immediate() doesn't set immediate.got in > err_out path. > > Unfortunately, insn_get_length() returns void, and I do not see any > insn-was-decoded-correctly helper. Perhaps we should simply remove > this WARN_ON() ?
Yes, it should just return an error, since user can miss the probe address on user binary and we can not make sure that is on a instruction boundary.
> Alternatively, If am right we can move this check down after the "good_insns" > checks, but this doesn't look very clean to me.
I think it is enough if arch_uprobe_analyze_insn() returns an error. That makes prepare_uprobe() fail and finally leads uprobe_register() fail.
Thank you,
> > > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > > Reported-by: syzbot+30d675e3ca03c1c351e7@syzkaller.appspotmail.com > > > > random: sshd: uninitialized urandom read (32 bytes read) > > random: sshd: uninitialized urandom read (32 bytes read) > > random: sshd: uninitialized urandom read (32 bytes read) > > random: sshd: uninitialized urandom read (32 bytes read) > > random: sshd: uninitialized urandom read (32 bytes read) > > WARNING: CPU: 0 PID: 4511 at arch/x86/kernel/uprobes.c:296 insn_complete > > arch/x86/include/asm/insn.h:147 [inline] > > WARNING: CPU: 0 PID: 4511 at arch/x86/kernel/uprobes.c:296 uprobe_init_insn > > arch/x86/kernel/uprobes.c:296 [inline] > > WARNING: CPU: 0 PID: 4511 at arch/x86/kernel/uprobes.c:296 > > arch_uprobe_analyze_insn+0x13d/0x15f0 arch/x86/kernel/uprobes.c:861 > > Kernel panic - not syncing: panic_on_warn set ... > > > > CPU: 0 PID: 4511 Comm: syz-executor347 Not tainted 4.17.0-rc4+ #46 > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS > > Google 01/01/2011 > > Call Trace: > > __dump_stack lib/dump_stack.c:77 [inline] > > dump_stack+0x1b9/0x294 lib/dump_stack.c:113 > > panic+0x22f/0x4de kernel/panic.c:184 > > __warn.cold.8+0x163/0x1b3 kernel/panic.c:536 > > report_bug+0x252/0x2d0 lib/bug.c:186 > > fixup_bug arch/x86/kernel/traps.c:178 [inline] > > do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296 > > do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315 > > invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992 > > RIP: 0010:insn_complete arch/x86/include/asm/insn.h:147 [inline] > > RIP: 0010:uprobe_init_insn arch/x86/kernel/uprobes.c:296 [inline] > > RIP: 0010:arch_uprobe_analyze_insn+0x13d/0x15f0 > > arch/x86/kernel/uprobes.c:861 > > RSP: 0018:ffff8801cf277510 EFLAGS: 00010246 > > RAX: 0000000000000000 RBX: ffff8801cf277560 RCX: ffffffff876ccf2a > > RDX: 0000000000000004 RSI: ffffffff876ce6ab RDI: ffff8801cf27759c > > RBP: ffff8801cf277628 R08: ffff8801d8c0a5c0 R09: ffff8801cf277560 > > R10: ffff8801d7ad81d0 R11: ffff8801cf2775af R12: 0000000000000000 > > R13: dffffc0000000000 R14: ffff8801d7ad8080 R15: ffff8801cf277600 > > prepare_uprobe kernel/events/uprobes.c:610 [inline] > > install_breakpoint.isra.21+0x710/0x830 kernel/events/uprobes.c:657 > > uprobe_mmap+0x6a0/0xcf0 kernel/events/uprobes.c:1089 > > mmap_region+0x5c8/0x1870 mm/mmap.c:1807 > > do_mmap+0xde2/0x1360 mm/mmap.c:1535 > > do_mmap_pgoff include/linux/mm.h:2237 [inline] > > vm_mmap_pgoff+0x1fb/0x2a0 mm/util.c:357 > > ksys_mmap_pgoff+0x4c9/0x640 mm/mmap.c:1585 > > __do_sys_mmap arch/x86/kernel/sys_x86_64.c:100 [inline] > > __se_sys_mmap arch/x86/kernel/sys_x86_64.c:91 [inline] > > __x64_sys_mmap+0xe9/0x1b0 arch/x86/kernel/sys_x86_64.c:91 > > do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287 > > entry_SYSCALL_64_after_hwframe+0x49/0xbe > > RIP: 0033:0x43ff29 > > RSP: 002b:00007ffc922a4898 EFLAGS: 00000212 ORIG_RAX: 0000000000000009 > > RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043ff29 > > RDX: 0000000000000000 RSI: 0000000000002000 RDI: 000000002000c000 > > RBP: 00000000006ca018 R08: 0000000000000003 R09: 0000000000000000 > > R10: 0000000000000012 R11: 0000000000000212 R12: 0000000000401850 > > R13: 00000000004018e0 R14: 0000000000000000 R15: 0000000000000000 > > Dumping ftrace buffer: > > (ftrace buffer empty) > > Kernel Offset: disabled > > Rebooting in 86400 seconds.. > > > > > > --- > > This bug 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@googlegroups.com. > > > > syzbot will keep track of this bug report. See: > > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with > > syzbot. > > syzbot can test patches for this bug, for details see: > > https://goo.gl/tpsmEJ#testing-patches >
-- Masami Hiramatsu <mhiramat@kernel.org>
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