Re: general protection fault in __radix_tree_delete

[Eric Biggers]

On Sun, May 13, 2018 at 10:26:15AM +0200, 'Dmitry Vyukov' via syzkaller-bugs wrote:
> On Sun, Apr 29, 2018 at 7:00 PM, syzbot
> <syzbot+549decbd1891d501b6d5@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hello,
> >
> > syzbot hit the following crash on upstream commit
> > cdface5209349930ae1b51338763c8e029971b97 (Sun Apr 29 03:07:21 2018 +0000)
> > Merge tag 'for_linus_stable' of
> > git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4
> > syzbot dashboard link:
> > https://syzkaller.appspot.com/bug?extid=549decbd1891d501b6d5
> >
> > So far this crash happened 8 times on upstream.
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?id=6647588371562496
> > syzkaller reproducer:
> > https://syzkaller.appspot.com/x/repro.syz?id=4781854846615552
> > Raw console output:
> > https://syzkaller.appspot.com/x/log.txt?id=4580574157078528
> > Kernel config:
> > https://syzkaller.appspot.com/x/.config?id=7043958930931867332
> > compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> >
> > IMPORTANT: if you fix the bug, please add the following tag to the commit:
> > Reported-by: syzbot+549decbd1891d501b6d5@xxxxxxxxxxxxxxxxxxxxxxxxx
> > It will help syzbot understand when the bug is fixed. See footer for
> > details.
> > If you forward the report, please keep this part and the footer.
> 
> 
> This crash was bisected as introduced by:
> 
> commit faeb7833eee0d6afe0ecb6bdfa6042556c2c352e
> Author: Roman Kagan <rkagan@xxxxxxxxxxxxx>
> Date:   Thu Feb 1 16:48:32 2018 +0300
> 
>     kvm: x86: hyperv: guest->host event signaling via eventfd
> 
> https://gist.githubusercontent.com/dvyukov/df4971d7dfd1b37bedb5bfa0c95f9ebc/raw/ee8b7804788049f80625563e0322090c798c4544/gistfile1.txt
> 
> 
> 
> > kasan: CONFIG_KASAN_INLINE enabled
> > kasan: GPF could be caused by NULL-ptr deref or user memory access
> > general protection fault: 0000 [#1] SMP KASAN
> > Dumping ftrace buffer:
> >    (ftrace buffer empty)
> > Modules linked in:
> > CPU: 0 PID: 4525 Comm: syz-executor786 Not tainted 4.17.0-rc2+ #23
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
> > Google 01/01/2011
> > RIP: 0010:__read_once_size include/linux/compiler.h:188 [inline]
> > RIP: 0010:__radix_tree_delete+0x74/0x230 lib/radix-tree.c:1989
> > RSP: 0018:ffff8801d9137108 EFLAGS: 00010206
> > RAX: 0000000000000003 RBX: dffffc0000000000 RCX: 1ffff1003b226e3e
> > RDX: 0000000000000000 RSI: ffffffff8768eeed RDI: ffff8801a7dac168
> > RBP: ffff8801d91371a8 R08: ffff8801d962c1c0 R09: ffffed0034fb5811
> > R10: ffff8801d91372b8 R11: ffff8801a7dac08f R12: 0000000000000000
> > R13: ffff8801a7dac168 R14: 0000000000000018 R15: ffff8801d9137230
> > FS:  0000000001df3880(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
> > CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > CR2: 0000000020000100 CR3: 00000001d9104000 CR4: 00000000001426f0
> > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > Call Trace:
> >  radix_tree_delete_item+0x148/0x2d0 lib/radix-tree.c:2050
> >  idr_remove+0x46/0x60 lib/idr.c:157
> >  kvm_hv_eventfd_deassign arch/x86/kvm/hyperv.c:1433 [inline]
> >  kvm_vm_ioctl_hv_eventfd+0x1df/0x24b arch/x86/kvm/hyperv.c:1451
> >  kvm_arch_vm_ioctl+0x155e/0x2690 arch/x86/kvm/x86.c:4563
> >  kvm_vm_ioctl+0x246/0x1d90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3100
> >  vfs_ioctl fs/ioctl.c:46 [inline]
> >  file_ioctl fs/ioctl.c:500 [inline]
> >  do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
> >  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
> >  __do_sys_ioctl fs/ioctl.c:708 [inline]
> >  __se_sys_ioctl fs/ioctl.c:706 [inline]
> >  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
> >  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
> >  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> > RIP: 0033:0x440069
> > RSP: 002b:00007ffcf0b02cd8 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
> > RAX: ffffffffffffffda RBX: 6d766b2f7665642f RCX: 0000000000440069
> > RDX: 0000000020000000 RSI: 000000004018aebd RDI: 00000000000000a9
> > RBP: 00000000006cb018 R08: 00007ffcf0b02cf0 R09: 00007ffcf0b02cf0
> > R10: 00007ffcf0b02cf0 R11: 0000000000000217 R12: 00000000004018a0
> > R13: 0000000000401930 R14: 0000000000000000 R15: 0000000000000000
> > Code: 3f 9a 88 48 c7 45 88 80 ee 68 87 c7 00 f1 f1 f1 f1 c7 40 04 00 f2 f2
> > f2 c7 40 08 f3 f3 f3 f3 e8 a3 51 10 fa 4c 89 f0 48 c1 e8 03 <80> 3c 18 00 0f
> > 85 97 01 00 00 48 8d 55 d8 4c 8d 7a c0 49 8b 1e
> > RIP: __read_once_size include/linux/compiler.h:188 [inline] RSP:
> > ffff8801d9137108
> > RIP: __radix_tree_delete+0x74/0x230 lib/radix-tree.c:1989 RSP:
> > ffff8801d9137108
> > ---[ end trace 79327005f044daef ]---
> >
> >
> > ---
> > This bug is generated by a dumb bot. It may contain errors.
> > See https://goo.gl/tpsmEJ for details.
> > Direct all questions to syzkaller@xxxxxxxxxxxxxxxxx
> >
> > syzbot will keep track of this bug report.
> > If you forgot to add the Reported-by tag, once the fix for this bug is
> > merged
> > into any tree, please reply to this email with:
> > #syz fix: exact-commit-title

This seems to have been another report of the IDR / radix tree bug now fixed by
commit 7a4deea1aa8b (thanks Matthew!):

#syz fix: idr: fix invalid ptr dereference on item delete

- Eric