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Thu, 18 Sep 2025 08:35:24 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id jVJbNEzEy2hDRwAAD6G6ig (envelope-from ); Thu, 18 Sep 2025 08:35:24 +0000 Message-ID: <867144d3-b05e-4ce2-8bb6-da01e10fbd73@suse.cz> Date: Thu, 18 Sep 2025 10:35:24 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] WARNING: bad unlock balance in copy_process Content-Language: en-US To: syzbot , Liam.Howlett@oracle.com, akpm@linux-foundation.org, bsegall@google.com, david@redhat.com, dietmar.eggemann@arm.com, juri.lelli@redhat.com, kees@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, mgorman@suse.de, mhocko@suse.com, mingo@redhat.com, peterz@infradead.org, rostedt@goodmis.org, rppt@kernel.org, surenb@google.com, syzkaller-bugs@googlegroups.com, vincent.guittot@linaro.org, vschneid@redhat.com, Sebastian Andrzej Siewior References: <68cb1cbd.050a0220.2ff435.0599.GAE@google.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Spamd-Result: default: False [-1.80 / 50.00]; BAYES_HAM(-3.00)[100.00%]; SUSPICIOUS_RECIPS(1.50)[]; NEURAL_HAM_LONG(-1.00)[-1.000]; URI_HIDDEN_PATH(1.00)[https://syzkaller.appspot.com/x/.config?x=b8b6789b42526d72]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; FUZZY_RATELIMITED(0.00)[rspamd.com]; MIME_TRACE(0.00)[0:+]; RCPT_COUNT_TWELVE(0.00)[22]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TAGGED_RCPT(0.00)[80cb3cc5c14fad191a10]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; SUBJECT_HAS_QUESTION(0.00)[] X-Spam-Flag: NO X-Spam-Level: X-Spam-Score: -1.80 On 9/17/25 22:40, syzbot wrote: > syzbot has found a reproducer for the following issue on: > > HEAD commit: 6edf2885ebeb 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=16d14c7c580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=b8b6789b42526d72 > dashboard link: https://syzkaller.appspot.com/bug?extid=80cb3cc5c14fad191a10 > compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8 > userspace arch: arm64 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=179d9f62580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11d14c7c580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/c72239eb6d76/disk-6edf2885.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/b67e9820b2be/vmlinux-6edf2885.xz > kernel image: https://storage.googleapis.com/syzbot-assets/0c4ab7e562f6/Image-6edf2885.gz.xz > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+80cb3cc5c14fad191a10@syzkaller.appspotmail.com > > ===================================== > WARNING: bad unlock balance detected! > syzkaller #0 Not tainted > ------------------------------------- > syz.1.48/6865 is trying to release lock (&sighand->siglock) at: > [] spin_unlock include/linux/spinlock.h:391 [inline] > [] copy_process+0x22d4/0x31ec kernel/fork.c:2432 bad_fork_core_free: sched_core_free(p); spin_unlock(¤t->sighand->siglock); <- here Sebastian, I think it's your 7c4f75a21f63 ("futex: Allow automatic allocation of process wide futex hash") adding a "goto bad_fork_core_free;" from a place that doesn't yet have current->sighand->siglock locked? > but there are no more locks to release! > > other info that might help us debug this: > 1 lock held by syz.1.48/6865: > #0: ffff80008fa00450 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2228/0x31ec kernel/fork.c:2274 > > stack backtrace: > CPU: 0 UID: 0 PID: 6865 Comm: syz.1.48 Not tainted syzkaller #0 PREEMPT > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025 > Call trace: > show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:499 (C) > __dump_stack+0x30/0x40 lib/dump_stack.c:94 > dump_stack_lvl+0xd8/0x12c lib/dump_stack.c:120 > dump_stack+0x1c/0x28 lib/dump_stack.c:129 > print_unlock_imbalance_bug+0xf4/0xfc kernel/locking/lockdep.c:5298 > __lock_release kernel/locking/lockdep.c:-1 [inline] > lock_release+0x244/0x39c kernel/locking/lockdep.c:5889 > __raw_spin_unlock include/linux/spinlock_api_smp.h:141 [inline] > _raw_spin_unlock+0x24/0x78 kernel/locking/spinlock.c:186 > spin_unlock include/linux/spinlock.h:391 [inline] > copy_process+0x22d4/0x31ec kernel/fork.c:2432 > kernel_clone+0x1d8/0x84c kernel/fork.c:2605 > __do_sys_clone kernel/fork.c:2748 [inline] > __se_sys_clone kernel/fork.c:2716 [inline] > __arm64_sys_clone+0x144/0x1a0 kernel/fork.c:2716 > __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] > invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 > el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 > do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 > el0_svc+0x5c/0x254 arch/arm64/kernel/entry-common.c:744 > el0t_64_sync_handler+0x84/0x12c arch/arm64/kernel/entry-common.c:763 > el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596 > > > --- > 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.