Message-ID: <6974c4c7.a00a0220.33ccc7.000a.GAE@google.com>
Date: Sat, 24 Jan 2026 05:10:31 -0800
From: syzbot <syzbot+90f65e574fb85432db68@...kaller.appspotmail.com>
To: axboe@...nel.dk, linux-block@...r.kernel.org, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: [syzbot] [block?] INFO: task hung in read_cache_folio (5)

Hello,

syzbot found the following issue on:

HEAD commit:    24d479d26b25 Linux 6.19-rc6
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1248cd22580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9ec857cfb59de463
dashboard link: https://syzkaller.appspot.com/bug?extid=90f65e574fb85432db68
compiler:       aarch64-linux-gnu-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/fa3fbcfdac58/non_bootable_disk-24d479d2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f4a697aeae5b/vmlinux-24d479d2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/df285e089d77/zImage-24d479d2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+90f65e574fb85432db68@...kaller.appspotmail.com

INFO: task udevd:6058 blocked for more than 430 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:0     pid:6058  tgid:6058  ppid:3136   task_flags:0x400140 flags:0x00000019
Call trace:
 __switch_to+0x208/0x4f0 arch/arm64/kernel/process.c:742 (T)
 context_switch kernel/sched/core.c:5260 [inline]
 __schedule+0xcfc/0x2fec kernel/sched/core.c:6867
 __schedule_loop kernel/sched/core.c:6949 [inline]
 schedule+0xd0/0x344 kernel/sched/core.c:6964
 io_schedule+0xac/0x114 kernel/sched/core.c:7791
 folio_wait_bit_common+0x2a4/0x630 mm/filemap.c:1323
 folio_put_wait_locked mm/filemap.c:1487 [inline]
 do_read_cache_folio+0x240/0x3f4 mm/filemap.c:4078
 read_cache_folio+0x44/0x6c mm/filemap.c:4128
 read_mapping_folio include/linux/pagemap.h:1017 [inline]
 read_part_sector+0xac/0x5f4 block/partitions/core.c:722
 msdos_partition+0xe4/0x1f3c block/partitions/msdos.c:592
 check_partition block/partitions/core.c:141 [inline]
 blk_add_partitions block/partitions/core.c:589 [inline]
 bdev_disk_changed+0x504/0xf08 block/partitions/core.c:693
 blkdev_get_whole+0x144/0x1e4 block/bdev.c:765
 bdev_open+0x1dc/0xa84 block/bdev.c:974
 blkdev_open+0x270/0x3dc block/fops.c:698
 do_dentry_open+0x3f4/0x10e4 fs/open.c:962
 vfs_open+0x5c/0x2fc fs/open.c:1094
 do_open fs/namei.c:4637 [inline]
 path_openat+0x17f0/0x28cc fs/namei.c:4796
 do_filp_open+0x184/0x360 fs/namei.c:4823
 do_sys_openat2+0xe0/0x188 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __arm64_sys_openat+0x12c/0x1bc fs/open.c:1447
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x40/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x54/0x2b0 arch/arm64/kernel/entry-common.c:724
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Showing all locks held in the system:
1 lock held by khungtaskd/32:
 #0: ffff800087552ae0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x18/0x1c4 kernel/locking/lockdep.c:6769
4 locks held by kworker/1:2/912:
 #0: ffff00000dc29948 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x6f8/0x18d4 kernel/workqueue.c:3232
 #1: ffff80008ec17c90 ((work_completion)(&helper->damage_work)){+.+.}-{0:0}, at: psi_task_switch+0x60/0x804 kernel/sched/psi.c:933
 #2: ffff00000fb4e160 (&helper->damage_lock){....}-{3:3}, at: drm_fb_helper_fb_dirty drivers/gpu/drm/drm_fb_helper.c:340 [inline]
 #2: ffff00000fb4e160 (&helper->damage_lock){....}-{3:3}, at: drm_fb_helper_damage_work+0x188/0x5d8 drivers/gpu/drm/drm_fb_helper.c:372
 #3: ffff00001489a128 (&dev->master_mutex){+.+.}-{4:4}, at: drm_master_internal_acquire+0x24/0x6c drivers/gpu/drm/drm_auth.c:435
1 lock held by syslogd/3121:
2 locks held by getty/3259:
 #0: ffff00001373d0a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff80008d8eb2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x3e8/0xdd0 drivers/tty/n_tty.c:2211
1 lock held by syz-executor/3321:
2 locks held by kworker/u8:10/4327:
 #0: ffff00000dc31148 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x6f8/0x18d4 kernel/workqueue.c:3232
 #1: ffff80008f437c90 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x71c/0x18d4 kernel/workqueue.c:3232
2 locks held by kworker/u8:11/4332:
 #0: ffff00000dc31148 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x6f8/0x18d4 kernel/workqueue.c:3232
 #1: ffff80008f417c90 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x71c/0x18d4 kernel/workqueue.c:3232
1 lock held by udevd/6058:
 #0: ffff000015305358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0x2c4/0xa84 block/bdev.c:962
2 locks held by kworker/u8:1/6356:
 #0: ffff00000dc31148 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x6f8/0x18d4 kernel/workqueue.c:3232
 #1: ffff8000a1f27c90 ((work_completion)(&sub_info->work)){+.+.}-{0:0}, at: process_one_work+0x71c/0x18d4 kernel/workqueue.c:3232
1 lock held by syz.0.1250/7258:
 #0: ffff000015305358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0x84/0xa84 block/bdev.c:962
3 locks held by modprobe/7800:
2 locks held by modprobe/7802:
2 locks held by kworker/u8:11/7804:

=============================================

INFO: task udevd:6058 blocked for more than 451 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:0     pid:6058  tgid:6058  ppid:3136   task_flags:0x400140 flags:0x00000019
Call trace:
 __switch_to+0x208/0x4f0 arch/arm64/kernel/process.c:742 (T)
 context_switch kernel/sched/core.c:5260 [inline]
 __schedule+0xcfc/0x2fec kernel/sched/core.c:6867
 __schedule_loop kernel/sched/core.c:6949 [inline]
 schedule+0xd0/0x344 kernel/sched/core.c:6964
 io_schedule+0xac/0x114 kernel/sched/core.c:7791
 folio_wait_bit_common+0x2a4/0x630 mm/filemap.c:1323
 folio_put_wait_locked mm/filemap.c:1487 [inline]
 do_read_cache_folio+0x240/0x3f4 mm/filemap.c:4078
 read_cache_folio+0x44/0x6c mm/filemap.c:4128
 read_mapping_folio include/linux/pagemap.h:1017 [inline]
 read_part_sector+0xac/0x5f4 block/partitions/core.c:722
 msdos_partition+0xe4/0x1f3c block/partitions/msdos.c:592
 check_partition block/partitions/core.c:141 [inline]
 blk_add_partitions block/partitions/core.c:589 [inline]
 bdev_disk_changed+0x504/0xf08 block/partitions/core.c:693
 blkdev_get_whole+0x144/0x1e4 block/bdev.c:765
 bdev_open+0x1dc/0xa84 block/bdev.c:974
 blkdev_open+0x270/0x3dc block/fops.c:698
 do_dentry_open+0x3f4/0x10e4 fs/open.c:962
 vfs_open+0x5c/0x2fc fs/open.c:1094
 do_open fs/namei.c:4637 [inline]
 path_openat+0x17f0/0x28cc fs/namei.c:4796
 do_filp_open+0x184/0x360 fs/namei.c:4823
 do_sys_openat2+0xe0/0x188 fs/open.c:1430
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __arm64_sys_openat+0x12c/0x1bc fs/open.c:1447
 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
 invoke_syscall+0x6c/0x258 arch/arm64/kernel/syscall.c:49
 el0_svc_common.constprop.0+0xac/0x230 arch/arm64/kernel/syscall.c:132
 do_el0_svc+0x40/0x58 arch/arm64/kernel/syscall.c:151
 el0_svc+0x54/0x2b0 arch/arm64/kernel/entry-common.c:724
 el0t_64_sync_handler+0xa0/0xe4 arch/arm64/kernel/entry-common.c:743
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:596

Showing all locks held in the system:
1 lock held by rcu_preempt/15:
1 lock held by khungtaskd/32:
 #0: ffff800087552ae0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x18/0x1c4 kernel/locking/lockdep.c:6769
1 lock held by syslogd/3121:
2 locks held by dhcpcd/3165:
 #0: ffff800088b7e8a8 (vlan_ioctl_mutex){+.+.}-{4:4}, at: sock_ioctl+0x418/0x5d4 net/socket.c:1337
 #1: ffff800088ba83c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x28 net/core/rtnetlink.c:80
2 locks held by getty/3259:
 #0: ffff00001373d0a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff80008d8eb2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x3e8/0xdd0 drivers/tty/n_tty.c:2211
5 locks held by kworker/u8:11/4332:
 #0: ffff00000e16b948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work+0x6f8/0x18d4 kernel/workqueue.c:3232
 #1: ffff80008f417c90 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work+0x71c/0x18d4 kernel/workqueue.c:3232
 #2: ffff800088b93230 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0xdc/0x75c net/core/net_namespace.c:670
 #3: ffff800088ba83c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x28 net/core/rtnetlink.c:80
 #4: ffff80008755b5f8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock+0x250/0x364 kernel/rcu/tree_exp.h:311
3 locks held by kworker/u8:0/5452:
1 lock held by udevd/6058:
 #0: ffff000015305358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0x2c4/0xa84 block/bdev.c:962
1 lock held by syz.0.1250/7258:
 #0: ffff000015305358 (&disk->open_mutex){+.+.}-{4:4}, at: bdev_open+0x84/0xa84 block/bdev.c:962
3 locks held by kworker/u8:6/7811:
 #0: ffff00000dc31948 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x6f8/0x18d4 kernel/workqueue.c:3232
 #1: ffff80008e307c90 ((linkwatch_work).work){+.+.}-{0:0}, at: process_one_work+0x71c/0x18d4 kernel/workqueue.c:3232
 #2: ffff800088ba83c8 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock+0x1c/0x28 net/core/rtnetlink.c:80

=============================================



---
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If the report is already addressed, let syzbot know by replying with:
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If you want to overwrite report's subsystems, reply with:
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