[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20240627163100.GC469122@cmpxchg.org>
Date: Thu, 27 Jun 2024 12:31:00 -0400
From: Johannes Weiner <hannes@...xchg.org>
To: syzbot <syzbot+b7f13b2d0cc156edf61a@...kaller.appspotmail.com>
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
lizefan.x@...edance.com, syzkaller-bugs@...glegroups.com,
tj@...nel.org, Nhat Pham <nphamcs@...il.com>
Subject: Re: [syzbot] [cgroups?] BUG: sleeping function called from invalid
context in cgroup_rstat_flush
On Thu, Jun 27, 2024 at 07:03:21AM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 7c16f0a4ed1c Merge tag 'i2c-for-6.10-rc5' of git://git.ker..
> git tree: upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1511528e980000
> kernel config: https://syzkaller.appspot.com/x/.config?x=12f98862a3c0c799
> dashboard link: https://syzkaller.appspot.com/bug?extid=b7f13b2d0cc156edf61a
> compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/50560e9024e5/disk-7c16f0a4.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/080c27daee72/vmlinux-7c16f0a4.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/c528e0da4544/bzImage-7c16f0a4.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+b7f13b2d0cc156edf61a@...kaller.appspotmail.com
>
> BUG: sleeping function called from invalid context at kernel/cgroup/rstat.c:351
> in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 17332, name: syz-executor.4
> preempt_count: 0, expected: 0
> RCU nest depth: 1, expected: 0
> 1 lock held by syz-executor.4/17332:
> #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
> #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
> #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: filemap_cachestat mm/filemap.c:4251 [inline]
> #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: __do_sys_cachestat mm/filemap.c:4407 [inline]
> #0: ffffffff8e333fa0 (rcu_read_lock){....}-{1:2}, at: __se_sys_cachestat+0x3ee/0xbb0 mm/filemap.c:4372
> CPU: 1 PID: 17332 Comm: syz-executor.4 Not tainted 6.10.0-rc4-syzkaller-00330-g7c16f0a4ed1c #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
> Call Trace:
> <TASK>
> __dump_stack lib/dump_stack.c:88 [inline]
> dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
> __might_resched+0x5d4/0x780 kernel/sched/core.c:10196
> cgroup_rstat_flush+0x1e/0x50 kernel/cgroup/rstat.c:351
> workingset_test_recent+0x48a/0xa90 mm/workingset.c:473
> filemap_cachestat mm/filemap.c:4314 [inline]
> __do_sys_cachestat mm/filemap.c:4407 [inline]
> __se_sys_cachestat+0x795/0xbb0 mm/filemap.c:4372
> do_syscall_x64 arch/x86/entry/common.c:52 [inline]
> do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
Ok yeah, cachestat() holds the rcu read lock, so
workingset_test_recent() can't do a sleepable rstat flush.
I think the easiest fix would be to flush rstat from the root down
(NULL) in filemap_cachestat(), before the rcu section, and add a flag
to workingset_test_recent() to forego it. Nhat?
Powered by blists - more mailing lists