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Date:   Thu, 6 Jul 2023 12:53:36 -0400
From:   "Liam R. Howlett" <Liam.Howlett@Oracle.com>
To:     syzbot <syzbot+8645fe63c4d22c8d27b8@syzkaller.appspotmail.com>
Cc:     akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [mm?] WARNING: suspicious RCU usage in mas_walk (2)
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This is a duplicate of what was reported on lkml and fixed by Linus [1].

[1.] https://lore.kernel.org/lkml/ZKIsoMOT71uwCIZX@xsang-OptiPlex-9020/

* syzbot <syzbot+8645fe63c4d22c8d27b8@syzkaller.appspotmail.com> [230705 23:22]:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a901a3568fd2 Merge tag 'iomap-6.5-merge-1' of git://git.ke..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=105632c8a80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=db74cd5aa6878807
> dashboard link: https://syzkaller.appspot.com/bug?extid=8645fe63c4d22c8d27b8
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/3e7b15164da6/disk-a901a356.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/9880c1d81d68/vmlinux-a901a356.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/6d5b0c0d9670/bzImage-a901a356.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8645fe63c4d22c8d27b8@syzkaller.appspotmail.com
> 
> SELinux:  policy capability cgroup_seclabel=1
> SELinux:  policy capability nnp_nosuid_transition=1
> SELinux:  policy capability genfs_seclabel_symlinks=0
> SELinux:  policy capability ioctl_skip_cloexec=0
> =============================
> WARNING: suspicious RCU usage
> 6.4.0-syzkaller-10173-ga901a3568fd2 #0 Not tainted
> -----------------------------
> lib/maple_tree.c:860 suspicious rcu_dereference_check() usage!
> 
> other info that might help us debug this:
> 
> 
> rcu_scheduler_active = 2, debug_locks = 1
> no locks held by init/1.
> 
> stack backtrace:
> CPU: 1 PID: 1 Comm: init Not tainted 6.4.0-syzkaller-10173-ga901a3568fd2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x136/0x150 lib/dump_stack.c:106
>  lockdep_rcu_suspicious+0x208/0x3a0 kernel/locking/lockdep.c:6719
>  mas_root lib/maple_tree.c:860 [inline]
>  mas_root lib/maple_tree.c:858 [inline]
>  mas_start lib/maple_tree.c:1402 [inline]
>  mas_start lib/maple_tree.c:1392 [inline]
>  mas_state_walk lib/maple_tree.c:3861 [inline]
>  mas_walk+0x4e8/0x7c0 lib/maple_tree.c:4980
>  mas_find_setup lib/maple_tree.c:5924 [inline]
>  mas_find+0x1cb/0x340 lib/maple_tree.c:5965
>  vma_next include/linux/mm.h:865 [inline]
>  validate_mm+0xd2/0x470 mm/mmap.c:301
>  do_vmi_align_munmap+0x1199/0x1680 mm/mmap.c:2561
>  do_vmi_munmap+0x266/0x430 mm/mmap.c:2619
>  __vm_munmap+0x137/0x380 mm/mmap.c:2899
>  __do_sys_munmap mm/mmap.c:2916 [inline]
>  __se_sys_munmap mm/mmap.c:2913 [inline]
>  __x64_sys_munmap+0x62/0x80 mm/mmap.c:2913
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f36cc8e9817
> Code: ff ff 76 10 48 8b 15 10 36 0d 00 f7 d8 64 89 02 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e1 35 0d 00 f7 d8 64 89 01 48
> RSP: 002b:00007fff12a54cf8 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
> RAX: ffffffffffffffda RBX: 000000000000001f RCX: 00007f36cc8e9817
> RDX: 0000000000000000 RSI: 00000000000415ce RDI: 00007f36cc6b1000
> RBP: 00005613cf216bf0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
> R13: 0000000000000000 R14: 00007f36cc6b1000 R15: 00007f36cc72a16d
>  </TASK>
> 
> =============================
> WARNING: suspicious RCU usage
> 6.4.0-syzkaller-10173-ga901a3568fd2 #0 Not tainted
> -----------------------------
> lib/maple_tree.c:816 suspicious rcu_dereference_check() usage!
> 
> other info that might help us debug this:
> 
> 
> rcu_scheduler_active = 2, debug_locks = 1
> no locks held by init/1.
> 
> stack backtrace:
> CPU: 0 PID: 1 Comm: init Not tainted 6.4.0-syzkaller-10173-ga901a3568fd2 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:88 [inline]
>  dump_stack_lvl+0x136/0x150 lib/dump_stack.c:106
>  lockdep_rcu_suspicious+0x208/0x3a0 kernel/locking/lockdep.c:6719
>  mt_slot lib/maple_tree.c:816 [inline]
>  mt_slot lib/maple_tree.c:813 [inline]
>  mtree_range_walk+0x602/0x940 lib/maple_tree.c:2976
>  mas_state_walk lib/maple_tree.c:3868 [inline]
>  mas_walk+0x393/0x7c0 lib/maple_tree.c:4980
>  mas_find_setup lib/maple_tree.c:5924 [inline]
>  mas_find+0x1cb/0x340 lib/maple_tree.c:5965
>  vma_next include/linux/mm.h:865 [inline]
>  validate_mm+0xd2/0x470 mm/mmap.c:301
>  do_vmi_align_munmap+0x1199/0x1680 mm/mmap.c:2561
>  do_vmi_munmap+0x266/0x430 mm/mmap.c:2619
>  __vm_munmap+0x137/0x380 mm/mmap.c:2899
>  __do_sys_munmap mm/mmap.c:2916 [inline]
>  __se_sys_munmap mm/mmap.c:2913 [inline]
>  __x64_sys_munmap+0x62/0x80 mm/mmap.c:2913
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7f36cc8e9817
> Code: ff ff 76 10 48 8b 15 10 36 0d 00 f7 d8 64 89 02 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 b8 0b 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d e1 35 0d 00 f7 d8 64 89 01 48
> RSP: 002b:00007fff12a54cf8 EFLAGS: 00000246 ORIG_RAX: 000000000000000b
> RAX: ffffffffffffffda RBX: 000000000000001f RCX: 00007f36cc8e9817
> RDX: 0000000000000000 RSI: 00000000000415ce RDI: 00007f36cc6b1000
> RBP: 00005613cf216bf0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000003
> R13: 0000000000000000 R14: 00007f36cc6b1000 R15: 00007f36cc72a16d
>  </TASK>
> 
> 
> ---
> This report 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 issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> 
> If the bug is already fixed, let syzbot know by replying with:
> #syz fix: exact-commit-title
> 
> If you want to change bug's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
> 
> If the bug is a duplicate of another bug, reply with:
> #syz dup: exact-subject-of-another-report
> 
> If you want to undo deduplication, reply with:
> #syz undup
>