[syzbot] [bcachefs?] possible deadlock in __bch2_disk_reservation_add

From: syzbot
Date: Fri Sep 13 2024 - 03:56:34 EST

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Hello,

syzbot found the following issue on:

HEAD commit: df54f4a16f82 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=123907c7980000
kernel config: https://syzkaller.appspot.com/x/.config?x=dde5a5ba8d41ee9e
dashboard link: https://syzkaller.appspot.com/bug?extid=089ffc4307915afa0da7
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/aa2eb06e0aea/disk-df54f4a1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/14728733d385/vmlinux-df54f4a1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/99816271407d/Image-df54f4a1.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+089ffc4307915afa0da7@xxxxxxxxxxxxxxxxxxxxxxxxx

======================================================
WARNING: possible circular locking dependency detected
6.11.0-rc5-syzkaller-gdf54f4a16f82 #0 Not tainted
------------------------------------------------------
syz.0.428/9213 is trying to acquire lock:
ffff0000f4c84990 (&c->mark_lock){++++}-{0:0}, at: __bch2_disk_reservation_add+0xc4/0x99c fs/bcachefs/buckets.c:1158

but task is already holding lock:
ffff0000d464a518 (sb_pagefaults#2){.+.+}-{0:0}, at: do_page_mkwrite+0x140/0x2dc mm/memory.c:3142

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #7 (sb_pagefaults#2){.+.+}-{0:0}:
percpu_down_read include/linux/percpu-rwsem.h:51 [inline]
__sb_start_write include/linux/fs.h:1675 [inline]
sb_start_pagefault include/linux/fs.h:1840 [inline]
bch2_page_mkwrite+0x280/0xe54 fs/bcachefs/fs-io-pagecache.c:614
do_page_mkwrite+0x140/0x2dc mm/memory.c:3142
do_shared_fault mm/memory.c:5133 [inline]
do_fault mm/memory.c:5195 [inline]
do_pte_missing mm/memory.c:3947 [inline]
handle_pte_fault+0x11d4/0x56f4 mm/memory.c:5521
__handle_mm_fault mm/memory.c:5664 [inline]
handle_mm_fault+0xe38/0x1460 mm/memory.c:5832
do_page_fault+0x428/0xb1c arch/arm64/mm/fault.c:613
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:690
do_mem_abort+0x74/0x200 arch/arm64/mm/fault.c:826
el0_da+0x60/0x178 arch/arm64/kernel/entry-common.c:580
el0t_64_sync_handler+0xcc/0xfc arch/arm64/kernel/entry-common.c:733
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

-> #6 (&mm->mmap_lock){++++}-{3:3}:
__might_fault+0xc4/0x124 mm/memory.c:6387
_inline_copy_to_user include/linux/uaccess.h:176 [inline]
copy_to_user include/linux/uaccess.h:207 [inline]
drm_mode_getconnector+0xaa4/0x1214 drivers/gpu/drm/drm_connector.c:3185
drm_ioctl_kernel+0x26c/0x368 drivers/gpu/drm/drm_ioctl.c:745
drm_ioctl+0x5e4/0xae4 drivers/gpu/drm/drm_ioctl.c:842
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:893
__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+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

-> #5 (&dev->mode_config.mutex){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
__mutex_lock kernel/locking/mutex.c:752 [inline]
mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
drm_client_modeset_probe+0x32c/0x3f78 drivers/gpu/drm/drm_client_modeset.c:834
__drm_fb_helper_initial_config_and_unlock+0xf0/0x19a4 drivers/gpu/drm/drm_fb_helper.c:1852
drm_fb_helper_initial_config+0x48/0x64 drivers/gpu/drm/drm_fb_helper.c:1940
drm_fbdev_shmem_client_hotplug+0x158/0x22c drivers/gpu/drm/drm_fbdev_shmem.c:250
drm_client_register+0x144/0x1e0 drivers/gpu/drm/drm_client.c:141
drm_fbdev_shmem_setup+0x11c/0x2cc drivers/gpu/drm/drm_fbdev_shmem.c:309
vkms_create drivers/gpu/drm/vkms/vkms_drv.c:226 [inline]
vkms_init+0x4f0/0x600 drivers/gpu/drm/vkms/vkms_drv.c:252
do_one_initcall+0x24c/0x9c0 init/main.c:1267
do_initcall_level+0x154/0x214 init/main.c:1329
do_initcalls+0x58/0xac init/main.c:1345
do_basic_setup+0x8c/0xa0 init/main.c:1364
kernel_init_freeable+0x324/0x478 init/main.c:1578
kernel_init+0x24/0x2a0 init/main.c:1467
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

-> #4 (&client->modeset_mutex){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
__mutex_lock kernel/locking/mutex.c:752 [inline]
mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
drm_client_modeset_probe+0x318/0x3f78 drivers/gpu/drm/drm_client_modeset.c:832
__drm_fb_helper_initial_config_and_unlock+0xf0/0x19a4 drivers/gpu/drm/drm_fb_helper.c:1852
drm_fb_helper_initial_config+0x48/0x64 drivers/gpu/drm/drm_fb_helper.c:1940
drm_fbdev_shmem_client_hotplug+0x158/0x22c drivers/gpu/drm/drm_fbdev_shmem.c:250
drm_client_register+0x144/0x1e0 drivers/gpu/drm/drm_client.c:141
drm_fbdev_shmem_setup+0x11c/0x2cc drivers/gpu/drm/drm_fbdev_shmem.c:309
vkms_create drivers/gpu/drm/vkms/vkms_drv.c:226 [inline]
vkms_init+0x4f0/0x600 drivers/gpu/drm/vkms/vkms_drv.c:252
do_one_initcall+0x24c/0x9c0 init/main.c:1267
do_initcall_level+0x154/0x214 init/main.c:1329
do_initcalls+0x58/0xac init/main.c:1345
do_basic_setup+0x8c/0xa0 init/main.c:1364
kernel_init_freeable+0x324/0x478 init/main.c:1578
kernel_init+0x24/0x2a0 init/main.c:1467
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

-> #3 (&helper->lock){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
__mutex_lock kernel/locking/mutex.c:752 [inline]
mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
__drm_fb_helper_restore_fbdev_mode_unlocked+0xb4/0x178 drivers/gpu/drm/drm_fb_helper.c:235
drm_fb_helper_set_par+0xc4/0x110 drivers/gpu/drm/drm_fb_helper.c:1351
fbcon_init+0xf34/0x1eb8 drivers/video/fbdev/core/fbcon.c:1093
visual_init+0x27c/0x548 drivers/tty/vt/vt.c:1011
do_bind_con_driver+0x7dc/0xe04 drivers/tty/vt/vt.c:3833
do_take_over_console+0x4ac/0x5f0 drivers/tty/vt/vt.c:4399
do_fbcon_takeover+0x158/0x260 drivers/video/fbdev/core/fbcon.c:531
do_fb_registered drivers/video/fbdev/core/fbcon.c:2968 [inline]
fbcon_fb_registered+0x370/0x4ec drivers/video/fbdev/core/fbcon.c:2988
do_register_framebuffer drivers/video/fbdev/core/fbmem.c:449 [inline]
register_framebuffer+0x470/0x610 drivers/video/fbdev/core/fbmem.c:515
__drm_fb_helper_initial_config_and_unlock+0x13b0/0x19a4 drivers/gpu/drm/drm_fb_helper.c:1875
drm_fb_helper_initial_config+0x48/0x64 drivers/gpu/drm/drm_fb_helper.c:1940
drm_fbdev_shmem_client_hotplug+0x158/0x22c drivers/gpu/drm/drm_fbdev_shmem.c:250
drm_client_register+0x144/0x1e0 drivers/gpu/drm/drm_client.c:141
drm_fbdev_shmem_setup+0x11c/0x2cc drivers/gpu/drm/drm_fbdev_shmem.c:309
vkms_create drivers/gpu/drm/vkms/vkms_drv.c:226 [inline]
vkms_init+0x4f0/0x600 drivers/gpu/drm/vkms/vkms_drv.c:252
do_one_initcall+0x24c/0x9c0 init/main.c:1267
do_initcall_level+0x154/0x214 init/main.c:1329
do_initcalls+0x58/0xac init/main.c:1345
do_basic_setup+0x8c/0xa0 init/main.c:1364
kernel_init_freeable+0x324/0x478 init/main.c:1578
kernel_init+0x24/0x2a0 init/main.c:1467
ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860

-> #2 (console_lock){+.+.}-{0:0}:
console_lock+0x19c/0x1f4 kernel/printk/printk.c:2735
__bch2_print_string_as_lines fs/bcachefs/util.c:267 [inline]
bch2_print_string_as_lines+0x2c/0xd4 fs/bcachefs/util.c:286
__bch2_fsck_err+0x16c0/0x278c fs/bcachefs/error.c:388
__bch2_bkey_fsck_err+0x7b0/0xea8 fs/bcachefs/error.c:436
bch2_alloc_v4_validate+0x9c4/0xd24
bch2_bkey_val_validate+0x114/0x1dc fs/bcachefs/bkey_methods.c:143
bch2_btree_node_read_done+0x36ec/0x4ab4 fs/bcachefs/btree_io.c:1219
btree_node_read_work+0x50c/0xe04 fs/bcachefs/btree_io.c:1323
bch2_btree_node_read+0x1f50/0x280c fs/bcachefs/btree_io.c:1708
__bch2_btree_root_read fs/bcachefs/btree_io.c:1749 [inline]
bch2_btree_root_read+0x2b0/0x53c fs/bcachefs/btree_io.c:1773
read_btree_roots+0x250/0x798 fs/bcachefs/recovery.c:523
bch2_fs_recovery+0x3278/0x5514 fs/bcachefs/recovery.c:851
bch2_fs_start+0x30c/0x53c fs/bcachefs/super.c:1036
bch2_fs_get_tree+0x938/0x1030 fs/bcachefs/fs.c:1946
vfs_get_tree+0x90/0x28c fs/super.c:1800
do_new_mount+0x278/0x900 fs/namespace.c:3472
path_mount+0x590/0xe04 fs/namespace.c:3799
do_mount fs/namespace.c:3812 [inline]
__do_sys_mount fs/namespace.c:4020 [inline]
__se_sys_mount fs/namespace.c:3997 [inline]
__arm64_sys_mount+0x45c/0x5a8 fs/namespace.c:3997
__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+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

-> #1 (&c->fsck_error_msgs_lock){+.+.}-{3:3}:
__mutex_lock_common+0x190/0x21a0 kernel/locking/mutex.c:608
__mutex_lock kernel/locking/mutex.c:752 [inline]
mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:804
__bch2_fsck_err+0x344/0x278c fs/bcachefs/error.c:267
bch2_check_fix_ptr fs/bcachefs/buckets.c:127 [inline]
bch2_check_fix_ptrs+0x1364/0x47f8 fs/bcachefs/buckets.c:256
bch2_trigger_extent+0x740/0x83c fs/bcachefs/buckets.c:844
bch2_key_trigger fs/bcachefs/bkey_methods.h:87 [inline]
bch2_gc_mark_key+0x4b4/0xb70 fs/bcachefs/btree_gc.c:633
bch2_gc_btree fs/bcachefs/btree_gc.c:669 [inline]
bch2_gc_btrees fs/bcachefs/btree_gc.c:728 [inline]
bch2_check_allocations+0x110c/0x4f64 fs/bcachefs/btree_gc.c:1135
bch2_run_recovery_pass+0xe4/0x1d4 fs/bcachefs/recovery_passes.c:183
bch2_run_recovery_passes+0x258/0x6e0 fs/bcachefs/recovery_passes.c:230
bch2_fs_recovery+0x32c8/0x5514 fs/bcachefs/recovery.c:859
bch2_fs_start+0x30c/0x53c fs/bcachefs/super.c:1036
bch2_fs_get_tree+0x938/0x1030 fs/bcachefs/fs.c:1946
vfs_get_tree+0x90/0x28c fs/super.c:1800
do_new_mount+0x278/0x900 fs/namespace.c:3472
path_mount+0x590/0xe04 fs/namespace.c:3799
do_mount fs/namespace.c:3812 [inline]
__do_sys_mount fs/namespace.c:4020 [inline]
__se_sys_mount fs/namespace.c:3997 [inline]
__arm64_sys_mount+0x45c/0x5a8 fs/namespace.c:3997
__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+0x54/0x168 arch/arm64/kernel/entry-common.c:712
el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

-> #0 (&c->mark_lock){++++}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3133 [inline]
check_prevs_add kernel/locking/lockdep.c:3252 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x33d8/0x779c kernel/locking/lockdep.c:5142
lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
percpu_down_read+0x5c/0x2e8 include/linux/percpu-rwsem.h:51
__bch2_disk_reservation_add+0xc4/0x99c fs/bcachefs/buckets.c:1158
bch2_disk_reservation_add+0x29c/0x460 fs/bcachefs/buckets.h:375
bch2_folio_reservation_get+0x2c4/0x5bc fs/bcachefs/fs-io-pagecache.c:445
bch2_page_mkwrite+0xa68/0xe54 fs/bcachefs/fs-io-pagecache.c:637
do_page_mkwrite+0x140/0x2dc mm/memory.c:3142
do_shared_fault mm/memory.c:5133 [inline]
do_fault mm/memory.c:5195 [inline]
do_pte_missing mm/memory.c:3947 [inline]
handle_pte_fault+0x11d4/0x56f4 mm/memory.c:5521
__handle_mm_fault mm/memory.c:5664 [inline]
handle_mm_fault+0xe38/0x1460 mm/memory.c:5832
do_page_fault+0x428/0xb1c arch/arm64/mm/fault.c:613
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:690
do_mem_abort+0x74/0x200 arch/arm64/mm/fault.c:826
el0_da+0x60/0x178 arch/arm64/kernel/entry-common.c:580
el0t_64_sync_handler+0xcc/0xfc arch/arm64/kernel/entry-common.c:733
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

other info that might help us debug this:

Chain exists of:
&c->mark_lock --> &mm->mmap_lock --> sb_pagefaults#2

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
rlock(sb_pagefaults#2);
lock(&mm->mmap_lock);
lock(sb_pagefaults#2);
rlock(&c->mark_lock);

*** DEADLOCK ***

2 locks held by syz.0.428/9213:
#0: ffff0000cec8a188 (&mm->mmap_lock){++++}-{3:3}, at: mmap_read_trylock include/linux/mmap_lock.h:163 [inline]
#0: ffff0000cec8a188 (&mm->mmap_lock){++++}-{3:3}, at: get_mmap_lock_carefully mm/memory.c:5869 [inline]
#0: ffff0000cec8a188 (&mm->mmap_lock){++++}-{3:3}, at: lock_mm_and_find_vma+0x38/0x2d8 mm/memory.c:5929
#1: ffff0000d464a518 (sb_pagefaults#2){.+.+}-{0:0}, at: do_page_mkwrite+0x140/0x2dc mm/memory.c:3142

stack backtrace:
CPU: 0 UID: 0 PID: 9213 Comm: syz.0.428 Not tainted 6.11.0-rc5-syzkaller-gdf54f4a16f82 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call trace:
dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:317
show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:324
__dump_stack lib/dump_stack.c:93 [inline]
dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:119
dump_stack+0x1c/0x28 lib/dump_stack.c:128
print_circular_bug+0x150/0x1b8 kernel/locking/lockdep.c:2059
check_noncircular+0x310/0x404 kernel/locking/lockdep.c:2186
check_prev_add kernel/locking/lockdep.c:3133 [inline]
check_prevs_add kernel/locking/lockdep.c:3252 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x33d8/0x779c kernel/locking/lockdep.c:5142
lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
percpu_down_read+0x5c/0x2e8 include/linux/percpu-rwsem.h:51
__bch2_disk_reservation_add+0xc4/0x99c fs/bcachefs/buckets.c:1158
bch2_disk_reservation_add+0x29c/0x460 fs/bcachefs/buckets.h:375
bch2_folio_reservation_get+0x2c4/0x5bc fs/bcachefs/fs-io-pagecache.c:445
bch2_page_mkwrite+0xa68/0xe54 fs/bcachefs/fs-io-pagecache.c:637
do_page_mkwrite+0x140/0x2dc mm/memory.c:3142
do_shared_fault mm/memory.c:5133 [inline]
do_fault mm/memory.c:5195 [inline]
do_pte_missing mm/memory.c:3947 [inline]
handle_pte_fault+0x11d4/0x56f4 mm/memory.c:5521
__handle_mm_fault mm/memory.c:5664 [inline]
handle_mm_fault+0xe38/0x1460 mm/memory.c:5832
do_page_fault+0x428/0xb1c arch/arm64/mm/fault.c:613
do_translation_fault+0xc4/0x114 arch/arm64/mm/fault.c:690
do_mem_abort+0x74/0x200 arch/arm64/mm/fault.c:826
el0_da+0x60/0x178 arch/arm64/kernel/entry-common.c:580
el0t_64_sync_handler+0xcc/0xfc arch/arm64/kernel/entry-common.c:733
el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598

---
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