linux-kernel - [syzbot] WARNING: suspicious RCU usage in mas_state

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Date:   Sun, 12 Feb 2023 22:16:41 -0800
From:   syzbot <syzbot+a5ca677fb59b73010889@...kaller.appspotmail.com>
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com, tj@...nel.org
Subject: [syzbot] WARNING: suspicious RCU usage in mas_state_walk (2)

Hello,

syzbot found the following issue on:

HEAD commit:    eaed33698e35 Merge branch 'for-next/core' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=16ce767d480000
kernel config:  https://syzkaller.appspot.com/x/.config?x=606ed7eeab569393
dashboard link: https://syzkaller.appspot.com/bug?extid=a5ca677fb59b73010889
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11a53365480000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=119c47f3480000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/39aaf563b17c/disk-eaed3369.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/83f46f733a0a/vmlinux-eaed3369.xz
kernel image: https://storage.googleapis.com/syzbot-assets/50dfdf867e68/Image-eaed3369.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a5ca677fb59b73010889@...kaller.appspotmail.com

=============================
WARNING: suspicious RCU usage
6.2.0-rc7-syzkaller-17891-geaed33698e35 #0 Not tainted
-----------------------------
lib/maple_tree.c:852 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
5 locks held by syz-executor154/5020:
 #0: ffff0000c672c460 (sb_writers#7){.+.+}-{0:0}, at: vfs_write+0x174/0x44c fs/read_write.c:580
 #1: ffff0000c9a67c88 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x120/0x288 fs/kernfs/file.c:325
 #2: ffff0000c03954a0 (kn->active#42){.+.+}-{0:0}, at: kernfs_fop_write_iter+0x128/0x288 fs/kernfs/file.c:326
 #3: ffff80000d4bc640 (ksm_thread_mutex){+.+.}-{3:3}, at: run_store+0x8c/0x608 mm/ksm.c:2951
 #4: ffff0000c6af9c48 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_lock include/linux/mmap_lock.h:117 [inline]
 #4: ffff0000c6af9c48 (&mm->mmap_lock){++++}-{3:3}, at: unmerge_and_remove_all_rmap_items mm/ksm.c:990 [inline]
 #4: ffff0000c6af9c48 (&mm->mmap_lock){++++}-{3:3}, at: run_store+0x200/0x608 mm/ksm.c:2957

stack backtrace:
CPU: 0 PID: 5020 Comm: syz-executor154 Not tainted 6.2.0-rc7-syzkaller-17891-geaed33698e35 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/21/2023
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd0/0x124 lib/dump_stack.c:106
 dump_stack+0x1c/0x28 lib/dump_stack.c:113
 lockdep_rcu_suspicious+0x138/0x154 kernel/locking/lockdep.c:6597
 mas_root lib/maple_tree.c:852 [inline]
 mas_start lib/maple_tree.c:1357 [inline]
 mas_state_walk+0x1a4/0x200 lib/maple_tree.c:3838
 mas_walk+0x2c/0xc4 lib/maple_tree.c:5046
 mas_find+0x10c/0x13c lib/maple_tree.c:6012
 vma_find include/linux/mm.h:668 [inline]
 vma_next include/linux/mm.h:677 [inline]
 unmerge_and_remove_all_rmap_items mm/ksm.c:991 [inline]
 run_store+0x214/0x608 mm/ksm.c:2957
 kobj_attr_store+0x4c/0x70 lib/kobject.c:824
 sysfs_kf_write+0xf4/0x11c fs/sysfs/file.c:136
 kernfs_fop_write_iter+0x1d8/0x288 fs/kernfs/file.c:334
 call_write_iter include/linux/fs.h:2189 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x2bc/0x44c fs/read_write.c:584
 ksys_write+0xb4/0x160 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __arm64_sys_write+0x24/0x34 fs/read_write.c:646
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x64/0x178 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0xbc/0x180 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x110 arch/arm64/kernel/syscall.c:193
 el0_svc+0x58/0x14c arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:591


---
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