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

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Date:   Tue, 25 Jul 2023 13:27:44 -0700
From:   syzbot <syzbot+8645fe63c4d22c8d27b8@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, liam.howlett@...cle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] WARNING: suspicious RCU usage in mas_walk (2)

syzbot has found a reproducer for the following issue on:

HEAD commit:    1e25dd777248 Add linux-next specific files for 20230725
git tree:       linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10ce2c31a80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f481ab36ce878b84
dashboard link: https://syzkaller.appspot.com/bug?extid=8645fe63c4d22c8d27b8
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=1697cec9a80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1566986ea80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e0c7408382e8/disk-1e25dd77.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c4b0f14b8c88/vmlinux-1e25dd77.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b38cfdfd7db8/bzImage-1e25dd77.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8645fe63c4d22c8d27b8@...kaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
6.5.0-rc3-next-20230725-syzkaller #0 Not tainted
-----------------------------
lib/maple_tree.c:839 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor244/5034:
 #0: ffff88802b3f0148 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:654 [inline]
 #0: ffff88802b3f0148 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x201/0x950 mm/memory.c:5585

stack backtrace:
CPU: 0 PID: 5034 Comm: syz-executor244 Not tainted 6.5.0-rc3-next-20230725-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
 lockdep_rcu_suspicious+0x20c/0x3b0 kernel/locking/lockdep.c:6719
 mas_root lib/maple_tree.c:839 [inline]
 mas_root lib/maple_tree.c:837 [inline]
 mas_start lib/maple_tree.c:1381 [inline]
 mas_state_walk lib/maple_tree.c:3832 [inline]
 mas_walk+0x55e/0x7d0 lib/maple_tree.c:4973
 find_mergeable_anon_vma+0x102/0x890 mm/mmap.c:1085
 __anon_vma_prepare+0x7d/0x550 mm/rmap.c:200
 anon_vma_prepare include/linux/rmap.h:159 [inline]
 wp_page_copy mm/memory.c:3202 [inline]
 do_wp_page+0x1bbf/0x2e10 mm/memory.c:3579
 handle_pte_fault mm/memory.c:5133 [inline]
 __handle_mm_fault+0x1704/0x4030 mm/memory.c:5257
 handle_mm_fault+0x47a/0xa00 mm/memory.c:5422
 do_user_addr_fault+0x2e7/0xfe0 arch/x86/mm/fault.c:1342
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x5c/0xd0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
RIP: 0033:0x7fbc6b3fd6e5
Code: 6a 00 41 b8 12 10 01 00 be 00 00 00 20 4c 8b 0d 21 9a 0a 00 bf 09 00 00 00 e8 37 2a 03 00 b9 00 04 00 20 ba 46 ae 20 40 31 c0 <c7> 04 25 00 04 00 20 00 00 00 00 be ff ff ff ff bf 10 00 00 00 c7
RSP: 002b:00007ffd68c881f0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007ffd68c883c8 RCX: 0000000020000400
RDX: 000000004020ae46 RSI: 0000000000400000 RDI: 0000000020000000
RBP: 00007fbc6b4a3610 R08: 0000000000000003 R09: 0000000000000000
R10: 0000000000011012 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffd68c883b8 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

=============================
WARNING: suspicious RCU usage
6.5.0-rc3-next-20230725-syzkaller #0 Not tainted
-----------------------------
lib/maple_tree.c:795 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor244/5034:
 #0: ffff88802b3f0148 (&vma->vm_lock->lock){++++}-{3:3}, at: vma_start_read include/linux/mm.h:654 [inline]
 #0: ffff88802b3f0148 (&vma->vm_lock->lock){++++}-{3:3}, at: lock_vma_under_rcu+0x201/0x950 mm/memory.c:5585

stack backtrace:
CPU: 0 PID: 5034 Comm: syz-executor244 Not tainted 6.5.0-rc3-next-20230725-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x125/0x1b0 lib/dump_stack.c:106
 lockdep_rcu_suspicious+0x20c/0x3b0 kernel/locking/lockdep.c:6719
 mt_slot lib/maple_tree.c:795 [inline]
 mt_slot lib/maple_tree.c:792 [inline]
 mtree_range_walk+0x6c5/0x9b0 lib/maple_tree.c:2946
 mas_state_walk lib/maple_tree.c:3839 [inline]
 mas_walk+0x389/0x7d0 lib/maple_tree.c:4973
 find_mergeable_anon_vma+0x102/0x890 mm/mmap.c:1085
 __anon_vma_prepare+0x7d/0x550 mm/rmap.c:200
 anon_vma_prepare include/linux/rmap.h:159 [inline]
 wp_page_copy mm/memory.c:3202 [inline]
 do_wp_page+0x1bbf/0x2e10 mm/memory.c:3579
 handle_pte_fault mm/memory.c:5133 [inline]
 __handle_mm_fault+0x1704/0x4030 mm/memory.c:5257
 handle_mm_fault+0x47a/0xa00 mm/memory.c:5422
 do_user_addr_fault+0x2e7/0xfe0 arch/x86/mm/fault.c:1342
 handle_page_fault arch/x86/mm/fault.c:1483 [inline]
 exc_page_fault+0x5c/0xd0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
RIP: 0033:0x7fbc6b3fd6e5
Code: 6a 00 41 b8 12 10 01 00 be 00 00 00 20 4c 8b 0d 21 9a 0a 00 bf 09 00 00 00 e8 37 2a 03 00 b9 00 04 00 20 ba 46 ae 20 40 31 c0 <c7> 04 25 00 04 00 20 00 00 00 00 be ff ff ff ff bf 10 00 00 00 c7
RSP: 002b:00007ffd68c881f0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 00007ffd68c883c8 RCX: 0000000020000400
RDX: 000000004020ae46 RSI: 0000000000400000 RDI: 0000000020000000
RBP: 00007fbc6b4a3610 R08: 0000000000000003 R09: 0000000000000000
R10: 000000000001101


---
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.