Re: [syzbot] KASAN: use-after-free Read in check_all_holdout_tasks_trace

On Tue, Jun 22, 2021 at 12:41 AM Paul E. McKenney [off-list ref] wrote:

On Sat, Jun 19, 2021 at 09:54:06AM -0700, syzbot wrote:

quoted

syzbot has bisected this issue to:

commit f9006acc8dfe59e25aa75729728ac57a8d84fc32
Author: Florian Westphal [off-list ref]
Date:   Wed Apr 21 07:51:08 2021 +0000

    netfilter: arp_tables: pass table pointer via nf_hook_ops

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10dceae8300000
start commit:   0c38740c selftests/bpf: Fix ringbuf test fetching map FD
git tree:       bpf-next
final oops:     https://syzkaller.appspot.com/x/report.txt?x=12dceae8300000
console output: https://syzkaller.appspot.com/x/log.txt?x=14dceae8300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a6380da8984033f1
dashboard link: https://syzkaller.appspot.com/bug?extid=7b2b13f4943374609532
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1264c2d7d00000

Reported-by: syzbot+7b2b13f4943374609532@syzkaller.appspotmail.com
Fixes: f9006acc8dfe ("netfilter: arp_tables: pass table pointer via nf_hook_ops")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

I am not seeing any mention of check_all_holdout_tasks_trace() in
the console output, but I again suggest the following two patches:

6a04a59eacbd ("rcu-tasks: Don't delete holdouts within trc_inspect_reader()"
dd5da0a9140e ("rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader()")

Let's tell syzbot about these fixes, then it will tell us if they help or not.

#syz fix: rcu-tasks: Don't delete holdouts within trc_inspect_reader()