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Fri, 27 Sep 2024 06:38:29 -0700 Received: from pek-lpd-ccm6.wrs.com (147.11.136.210) by ALA-EXCHNG02.corp.ad.wrs.com (147.11.82.254) with Microsoft SMTP Server id 15.1.2507.39 via Frontend Transport; Fri, 27 Sep 2024 06:38:26 -0700 From: Lizhi Xu To: CC: , , , , , , , Subject: [PATCH V2] inotify: Fix possible deadlock in fsnotify_destroy_mark Date: Fri, 27 Sep 2024 21:38:26 +0800 Message-ID: <20240927133826.2037827-1-lizhi.xu@windriver.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240927102050.cfr4ovprdbgiicgk@quack3> References: <20240927102050.cfr4ovprdbgiicgk@quack3> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Proofpoint-ORIG-GUID: z3wfENa62nUhi0JXx87v3rUroaVjfLMo X-Authority-Analysis: v=2.4 cv=bas5U/PB c=1 sm=1 tr=0 ts=66f6b556 cx=c_pps a=K4BcnWQioVPsTJd46EJO2w==:117 a=K4BcnWQioVPsTJd46EJO2w==:17 a=EaEq8P2WXUwA:10 a=hSkVLCK3AAAA:8 a=edf1wS77AAAA:8 a=t7CeM3EgAAAA:8 a=JEpJUzSd5mD0hPGLkQkA:9 a=cQPPKAXgyycSBL8etih5:22 a=DcSpbTIhAlouE1Uv7lRv:22 a=FdTzh2GWekK77mhwV6Dw:22 X-Proofpoint-GUID: z3wfENa62nUhi0JXx87v3rUroaVjfLMo X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1051,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-27_06,2024-09-27_01,2024-09-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 bulkscore=0 mlxscore=0 adultscore=0 lowpriorityscore=0 suspectscore=0 malwarescore=0 mlxlogscore=695 clxscore=1015 priorityscore=1501 spamscore=0 phishscore=0 classifier=spam authscore=0 adjust=0 reason=mlx scancount=1 engine=8.21.0-2408220000 definitions=main-2409270098 Content-Type: text/plain; charset="utf-8" [Syzbot reported] WARNING: possible circular locking dependency detected 6.11.0-rc4-syzkaller-00019-gb311c1b497e5 #0 Not tainted ------------------------------------------------------ kswapd0/78 is trying to acquire lock: ffff88801b8d8930 (&group->mark_mutex){+.+.}-{3:3}, at: fsnotify_group_lock = include/linux/fsnotify_backend.h:270 [inline] ffff88801b8d8930 (&group->mark_mutex){+.+.}-{3:3}, at: fsnotify_destroy_mar= k+0x38/0x3c0 fs/notify/mark.c:578 but task is already holding lock: ffffffff8ea2fd60 (fs_reclaim){+.+.}-{0:0}, at: balance_pgdat mm/vmscan.c:68= 41 [inline] ffffffff8ea2fd60 (fs_reclaim){+.+.}-{0:0}, at: kswapd+0xbb4/0x35a0 mm/vmsca= n.c:7223 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}-{0:0}: lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 __fs_reclaim_acquire mm/page_alloc.c:3818 [inline] fs_reclaim_acquire+0x88/0x140 mm/page_alloc.c:3832 might_alloc include/linux/sched/mm.h:334 [inline] slab_pre_alloc_hook mm/slub.c:3939 [inline] slab_alloc_node mm/slub.c:4017 [inline] kmem_cache_alloc_noprof+0x3d/0x2a0 mm/slub.c:4044 inotify_new_watch fs/notify/inotify/inotify_user.c:599 [inline] inotify_update_watch fs/notify/inotify/inotify_user.c:647 [inline] __do_sys_inotify_add_watch fs/notify/inotify/inotify_user.c:786 [inl= ine] __se_sys_inotify_add_watch+0x72e/0x1070 fs/notify/inotify/inotify_us= er.c:729 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 -> #0 (&group->mark_mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3133 [inline] check_prevs_add kernel/locking/lockdep.c:3252 [inline] validate_chain+0x18e0/0x5900 kernel/locking/lockdep.c:3868 __lock_acquire+0x137a/0x2040 kernel/locking/lockdep.c:5142 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 fsnotify_group_lock include/linux/fsnotify_backend.h:270 [inline] fsnotify_destroy_mark+0x38/0x3c0 fs/notify/mark.c:578 fsnotify_destroy_marks+0x14a/0x660 fs/notify/mark.c:934 fsnotify_inoderemove include/linux/fsnotify.h:264 [inline] dentry_unlink_inode+0x2e0/0x430 fs/dcache.c:403 __dentry_kill+0x20d/0x630 fs/dcache.c:610 shrink_kill+0xa9/0x2c0 fs/dcache.c:1055 shrink_dentry_list+0x2c0/0x5b0 fs/dcache.c:1082 prune_dcache_sb+0x10f/0x180 fs/dcache.c:1163 super_cache_scan+0x34f/0x4b0 fs/super.c:221 do_shrink_slab+0x701/0x1160 mm/shrinker.c:435 shrink_slab+0x1093/0x14d0 mm/shrinker.c:662 shrink_one+0x43b/0x850 mm/vmscan.c:4815 shrink_many mm/vmscan.c:4876 [inline] lru_gen_shrink_node mm/vmscan.c:4954 [inline] shrink_node+0x3799/0x3de0 mm/vmscan.c:5934 kswapd_shrink_node mm/vmscan.c:6762 [inline] balance_pgdat mm/vmscan.c:6954 [inline] kswapd+0x1bcd/0x35a0 mm/vmscan.c:7223 kthread+0x2f0/0x390 kernel/kthread.c:389 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&group->mark_mutex); lock(fs_reclaim); lock(&group->mark_mutex); *** DEADLOCK *** [Analysis]=20 The inotify_new_watch() call passes through GFP_KERNEL, use memalloc_nofs_s= ave/ memalloc_nofs_restore to make sure we don't end up with the fs reclaim depe= ndency. That any notification group needs to use NOFS allocations to be safe against this race so we can just remove FSNOTIFY_GROUP_NOFS and unconditionally do memalloc_nofs_save() in fsnotify_group_lock(). Reported-and-tested-by: syzbot+c679f13773f295d2da53@syzkaller.appspotmail.c= om Closes: https://syzkaller.appspot.com/bug?extid=3Dc679f13773f295d2da53 Signed-off-by: Lizhi Xu --- V1 -> V2: remove FSNOTIFY_GROUP_NOFS in fsnotify_group_lock and unlock fs/notify/inotify/inotify_user.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_back= end.h index 8be029bc50b1..7b0a2809fc2d 100644 --- a/include/linux/fsnotify_backend.h +++ b/include/linux/fsnotify_backend.h @@ -268,14 +268,12 @@ struct fsnotify_group { static inline void fsnotify_group_lock(struct fsnotify_group *group) { mutex_lock(&group->mark_mutex); - if (group->flags & FSNOTIFY_GROUP_NOFS) - group->owner_flags =3D memalloc_nofs_save(); + group->owner_flags =3D memalloc_nofs_save(); } =20 static inline void fsnotify_group_unlock(struct fsnotify_group *group) { - if (group->flags & FSNOTIFY_GROUP_NOFS) - memalloc_nofs_restore(group->owner_flags); + memalloc_nofs_restore(group->owner_flags); mutex_unlock(&group->mark_mutex); } =20 --=20 2.43.0