linux-kernel - Re: [syzbot] [mm?] WARNING: suspicious RCU usage in mas

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Message-ID: <0000000000006cab1e06087302dd@google.com>
Date:   Tue, 24 Oct 2023 02:31:55 -0700
From:   syzbot <syzbot+79fcba037b6df73756d3@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, hughd@...gle.com,
        liam.howlett@...cle.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, postmaster@...gon.onmicrosoft.com,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] WARNING: suspicious RCU usage in mas_walk (3)

syzbot has found a reproducer for the following issue on:

HEAD commit:    e8361b005d7c Add linux-next specific files for 20231023
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1535f3a3680000
kernel config:  https://syzkaller.appspot.com/x/.config?x=39bda8753f457952
dashboard link: https://syzkaller.appspot.com/bug?extid=79fcba037b6df73756d3
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13714705680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1236430b680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f6e9b9de3681/disk-e8361b00.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5aadf3761d05/vmlinux-e8361b00.xz
kernel image: https://storage.googleapis.com/syzbot-assets/704f56d3327c/bzImage-e8361b00.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+79fcba037b6df73756d3@...kaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
6.6.0-rc6-next-20231023-syzkaller #0 Not tainted
-----------------------------
lib/maple_tree.c:856 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
no locks held by syz-executor445/16542.

stack backtrace:
CPU: 1 PID: 16542 Comm: syz-executor445 Not tainted 6.6.0-rc6-next-20231023-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
 lockdep_rcu_suspicious+0x20b/0x3a0 kernel/locking/lockdep.c:6711
 mas_root lib/maple_tree.c:856 [inline]
 mas_root lib/maple_tree.c:854 [inline]
 mas_start lib/maple_tree.c:1385 [inline]
 mas_state_walk lib/maple_tree.c:3705 [inline]
 mas_walk+0x4d1/0x7d0 lib/maple_tree.c:4888
 mas_find_setup lib/maple_tree.c:5948 [inline]
 mas_find+0x1e6/0x400 lib/maple_tree.c:5989
 vma_find include/linux/mm.h:952 [inline]
 do_mbind+0xc8f/0x1010 mm/mempolicy.c:1328
 kernel_mbind+0x1d4/0x1f0 mm/mempolicy.c:1486
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x62/0x6a
RIP: 0033:0x7f384f7bd229
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 1d 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f384f753158 EFLAGS: 00000212 ORIG_RAX: 00000000000000ed
RAX: ffffffffffffffda RBX: 00007f384f8413f8 RCX: 00007f384f7bd229
RDX: 0000000000000003 RSI: 0000000000005000 RDI: 0000000020182000
RBP: 00007f384f8413f0 R08: 000000000000007f R09: 0000000000000003
R10: 0000000020000040 R11: 0000000000000212 R12: 00007f384f8413fc
R13: 000000000000006e R14: 00007ffdafb5ca20 R15: 00007ffdafb5cb08
 </TASK>

=============================
WARNING: suspicious RCU usage
6.6.0-rc6-next-20231023-syzkaller #0 Not tainted
-----------------------------
lib/maple_tree.c:812 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
no locks held by syz-executor445/16542.

stack backtrace:
CPU: 0 PID: 16542 Comm: syz-executor445 Not tainted 6.6.0-rc6-next-20231023-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
 lockdep_rcu_suspicious+0x20b/0x3a0 kernel/locking/lockdep.c:6711
 mt_slot lib/maple_tree.c:812 [inline]
 mt_slot lib/maple_tree.c:809 [inline]
 mtree_range_walk+0x6c5/0x9b0 lib/maple_tree.c:2827
 mas_state_walk lib/maple_tree.c:3712 [inline]
 mas_walk+0x374/0x7d0 lib/maple_tree.c:4888
 mas_find_setup lib/maple_tree.c:5948 [inline]
 mas_find+0x1e6/0x400 lib/maple_tree.c:5989
 vma_find include/linux/mm.h:952 [inline]
 do_mbind+0xc8f/0x1010 mm/mempolicy.c:1328
 kernel_mbind+0x1d4/0x1f0 mm/mempolicy.c:1486
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x62/0x6a
RIP: 0033:0x7f384f7bd229
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 81 1d 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f384f753158 EFLAGS: 00000212 ORIG_RAX: 00000000000000ed
RAX: ffffffffffffffda RBX: 00007f384f8413f8 RCX: 00007f384f7bd229
RDX: 0000000000000003 RSI: 0000000000005000 RDI: 0000000020182000
RBP: 00007f384f8413f0 R08: 000000000000007f R09: 0000000000000003
R10: 0000000020000040 R11: 0000000000000212 R12: 00007f384f8413fc
R13: 000000000000006e R14: 00007ffdafb5ca20 R15: 00007ffdafb5cb08
 </TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.