syzbot

======================================================
WARNING: possible circular locking dependency detected
6.15.0-rc5-syzkaller-gc32f8dc5aaf9 #0 Not tainted
------------------------------------------------------
syz.1.455/8130 is trying to acquire lock:
ffff0000dd4e78d0 (&mm->mmap_lock){++++}-{4:4}, at: __might_fault+0x9c/0x124 mm/memory.c:7150

but task is already holding lock:
ffff80009c4e7918 (crtc_ww_class_mutex){+.+.}-{4:4}, at: drm_mode_atomic_ioctl+0x3b0/0xde4 drivers/gpu/drm/drm_atomic_uapi.c:1444

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #9 (crtc_ww_class_mutex){+.+.}-{4:4}:
       ww_acquire_init include/linux/ww_mutex.h:162 [inline]
       drm_modeset_acquire_init+0x1d8/0x374 drivers/gpu/drm/drm_modeset_lock.c:250
       drmm_mode_config_init+0xb0c/0x10d8 drivers/gpu/drm/drm_mode_config.c:462
       vkms_modeset_init drivers/gpu/drm/vkms/vkms_drv.c:146 [inline]
       vkms_create drivers/gpu/drm/vkms/vkms_drv.c:207 [inline]
       vkms_init+0x2c0/0x5ac drivers/gpu/drm/vkms/vkms_drv.c:242
       do_one_initcall+0x250/0x990 init/main.c:1257
       do_initcall_level+0x154/0x214 init/main.c:1319
       do_initcalls+0x84/0xf4 init/main.c:1335
       do_basic_setup+0x8c/0xa0 init/main.c:1354
       kernel_init_freeable+0x2dc/0x444 init/main.c:1567
       kernel_init+0x24/0x1dc init/main.c:1457
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

-> #8 (crtc_ww_class_acquire){+.+.}-{0:0}:
       ww_acquire_init include/linux/ww_mutex.h:161 [inline]
       drm_modeset_acquire_init+0x1b8/0x374 drivers/gpu/drm/drm_modeset_lock.c:250
       drm_client_modeset_commit_atomic+0xcc/0x6ac drivers/gpu/drm/drm_client_modeset.c:1018
       drm_client_modeset_commit_locked+0xd0/0x4a0 drivers/gpu/drm/drm_client_modeset.c:1182
       drm_client_modeset_commit+0x50/0x7c drivers/gpu/drm/drm_client_modeset.c:1208
       __drm_fb_helper_restore_fbdev_mode_unlocked+0x94/0x198 drivers/gpu/drm/drm_fb_helper.c:237
       drm_fb_helper_set_par+0xa4/0x108 drivers/gpu/drm/drm_fb_helper.c:1359
       fbcon_init+0xe4c/0x1d18 drivers/video/fbdev/core/fbcon.c:1112
       visual_init+0x27c/0x540 drivers/tty/vt/vt.c:1011
       do_bind_con_driver+0x7b8/0xdd8 drivers/tty/vt/vt.c:3831
       do_take_over_console+0x824/0x97c drivers/tty/vt/vt.c:4397
       do_fbcon_takeover+0x158/0x25c drivers/video/fbdev/core/fbcon.c:548
       do_fb_registered drivers/video/fbdev/core/fbcon.c:2989 [inline]
       fbcon_fb_registered+0x354/0x4c8 drivers/video/fbdev/core/fbcon.c:3009
       do_register_framebuffer drivers/video/fbdev/core/fbmem.c:449 [inline]
       register_framebuffer+0x44c/0x5ec drivers/video/fbdev/core/fbmem.c:515
       __drm_fb_helper_initial_config_and_unlock+0x103c/0x159c drivers/gpu/drm/drm_fb_helper.c:1851
       drm_fb_helper_initial_config+0x3c/0x58 drivers/gpu/drm/drm_fb_helper.c:1916
       drm_fbdev_client_hotplug+0x154/0x22c drivers/gpu/drm/clients/drm_fbdev_client.c:52
       drm_client_register+0x13c/0x1d4 drivers/gpu/drm/drm_client.c:140
       drm_fbdev_client_setup+0x194/0x3d0 drivers/gpu/drm/clients/drm_fbdev_client.c:159
       drm_client_setup+0x78/0x140 drivers/gpu/drm/clients/drm_client_setup.c:39
       vkms_create drivers/gpu/drm/vkms/vkms_drv.c:218 [inline]
       vkms_init+0x4b8/0x5ac drivers/gpu/drm/vkms/vkms_drv.c:242
       do_one_initcall+0x250/0x990 init/main.c:1257
       do_initcall_level+0x154/0x214 init/main.c:1319
       do_initcalls+0x84/0xf4 init/main.c:1335
       do_basic_setup+0x8c/0xa0 init/main.c:1354
       kernel_init_freeable+0x2dc/0x444 init/main.c:1567
       kernel_init+0x24/0x1dc init/main.c:1457
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

-> #7 (&client->modeset_mutex){+.+.}-{4:4}:
       __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:601
       __mutex_lock kernel/locking/mutex.c:746 [inline]
       mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:798
       drm_client_modeset_probe+0x2f0/0x4e88 drivers/gpu/drm/drm_client_modeset.c:843
       __drm_fb_helper_initial_config_and_unlock+0xf0/0x159c drivers/gpu/drm/drm_fb_helper.c:1828
       drm_fb_helper_initial_config+0x3c/0x58 drivers/gpu/drm/drm_fb_helper.c:1916
       drm_fbdev_client_hotplug+0x154/0x22c drivers/gpu/drm/clients/drm_fbdev_client.c:52
       drm_client_register+0x13c/0x1d4 drivers/gpu/drm/drm_client.c:140
       drm_fbdev_client_setup+0x194/0x3d0 drivers/gpu/drm/clients/drm_fbdev_client.c:159
       drm_client_setup+0x78/0x140 drivers/gpu/drm/clients/drm_client_setup.c:39
       vkms_create drivers/gpu/drm/vkms/vkms_drv.c:218 [inline]
       vkms_init+0x4b8/0x5ac drivers/gpu/drm/vkms/vkms_drv.c:242
       do_one_initcall+0x250/0x990 init/main.c:1257
       do_initcall_level+0x154/0x214 init/main.c:1319
       do_initcalls+0x84/0xf4 init/main.c:1335
       do_basic_setup+0x8c/0xa0 init/main.c:1354
       kernel_init_freeable+0x2dc/0x444 init/main.c:1567
       kernel_init+0x24/0x1dc init/main.c:1457
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

-> #6 (&helper->lock){+.+.}-{4:4}:
       __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:601
       __mutex_lock kernel/locking/mutex.c:746 [inline]
       mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:798
       __drm_fb_helper_restore_fbdev_mode_unlocked+0x74/0x198 drivers/gpu/drm/drm_fb_helper.c:228
       drm_fb_helper_set_par+0xa4/0x108 drivers/gpu/drm/drm_fb_helper.c:1359
       fbcon_init+0xe4c/0x1d18 drivers/video/fbdev/core/fbcon.c:1112
       visual_init+0x27c/0x540 drivers/tty/vt/vt.c:1011
       do_bind_con_driver+0x7b8/0xdd8 drivers/tty/vt/vt.c:3831
       do_take_over_console+0x824/0x97c drivers/tty/vt/vt.c:4397
       do_fbcon_takeover+0x158/0x25c drivers/video/fbdev/core/fbcon.c:548
       do_fb_registered drivers/video/fbdev/core/fbcon.c:2989 [inline]
       fbcon_fb_registered+0x354/0x4c8 drivers/video/fbdev/core/fbcon.c:3009
       do_register_framebuffer drivers/video/fbdev/core/fbmem.c:449 [inline]
       register_framebuffer+0x44c/0x5ec drivers/video/fbdev/core/fbmem.c:515
       __drm_fb_helper_initial_config_and_unlock+0x103c/0x159c drivers/gpu/drm/drm_fb_helper.c:1851
       drm_fb_helper_initial_config+0x3c/0x58 drivers/gpu/drm/drm_fb_helper.c:1916
       drm_fbdev_client_hotplug+0x154/0x22c drivers/gpu/drm/clients/drm_fbdev_client.c:52
       drm_client_register+0x13c/0x1d4 drivers/gpu/drm/drm_client.c:140
       drm_fbdev_client_setup+0x194/0x3d0 drivers/gpu/drm/clients/drm_fbdev_client.c:159
       drm_client_setup+0x78/0x140 drivers/gpu/drm/clients/drm_client_setup.c:39
       vkms_create drivers/gpu/drm/vkms/vkms_drv.c:218 [inline]
       vkms_init+0x4b8/0x5ac drivers/gpu/drm/vkms/vkms_drv.c:242
       do_one_initcall+0x250/0x990 init/main.c:1257
       do_initcall_level+0x154/0x214 init/main.c:1319
       do_initcalls+0x84/0xf4 init/main.c:1335
       do_basic_setup+0x8c/0xa0 init/main.c:1354
       kernel_init_freeable+0x2dc/0x444 init/main.c:1567
       kernel_init+0x24/0x1dc init/main.c:1457
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

-> #5 (console_lock){+.+.}-{0:0}:
       console_lock+0x194/0x1ec kernel/printk/printk.c:2849
       __bch2_print_string_as_lines fs/bcachefs/util.c:267 [inline]
       bch2_print_string_as_lines+0x34/0x150 fs/bcachefs/util.c:286
       __bch2_fsck_err+0xb5c/0xdd0 fs/bcachefs/error.c:562
       __need_discard_or_freespace_err+0x14c/0x1cc fs/bcachefs/alloc_background.c:678
       bch2_bucket_do_index+0x320/0x490 fs/bcachefs/alloc_background.c:729
       bch2_trigger_alloc+0xd1c/0x2d54 fs/bcachefs/alloc_background.c:885
       bch2_key_trigger fs/bcachefs/bkey_methods.h:88 [inline]
       bch2_key_trigger_new fs/bcachefs/bkey_methods.h:116 [inline]
       run_one_trans_trigger fs/bcachefs/btree_trans_commit.c:516 [inline]
       bch2_trans_commit_run_triggers fs/bcachefs/btree_trans_commit.c:550 [inline]
       __bch2_trans_commit+0x634/0x62d0 fs/bcachefs/btree_trans_commit.c:990
       bch2_trans_commit fs/bcachefs/btree_update.h:195 [inline]
       btree_update_nodes_written fs/bcachefs/btree_update_interior.c:705 [inline]
       btree_interior_update_work+0xb80/0x1cfc fs/bcachefs/btree_update_interior.c:843
       process_one_work+0x7e8/0x156c kernel/workqueue.c:3238
       process_scheduled_works kernel/workqueue.c:3319 [inline]
       worker_thread+0x958/0xed8 kernel/workqueue.c:3400
       kthread+0x5fc/0x75c kernel/kthread.c:464
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

-> #4 (&c->fsck_error_msgs_lock){+.+.}-{4:4}:
       __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:601
       __mutex_lock kernel/locking/mutex.c:746 [inline]
       mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:798
       __bch2_count_fsck_err+0x58/0x98 fs/bcachefs/error.c:385
       __bch2_i_sectors_acct+0x328/0x3c4 fs/bcachefs/fs-io.c:155
       bch2_i_sectors_acct fs/bcachefs/fs-io.h:138 [inline]
       bchfs_fpunch+0x23c/0x404 fs/bcachefs/fs-io.c:578
       bch2_fallocate_dispatch+0x378/0x4e0 fs/bcachefs/fs-io.c:838
       vfs_fallocate+0x5cc/0x73c fs/open.c:338
       ioctl_preallocate fs/ioctl.c:290 [inline]
       file_ioctl fs/ioctl.c:-1 [inline]
       do_vfs_ioctl+0x1d4c/0x2218 fs/ioctl.c:885
       __do_sys_ioctl fs/ioctl.c:904 [inline]
       __se_sys_ioctl fs/ioctl.c:892 [inline]
       __arm64_sys_ioctl+0xe4/0x1c4 fs/ioctl.c:892
       __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+0x58/0x17c arch/arm64/kernel/entry-common.c:767
       el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

-> #3 (&inode->ei_quota_lock){+.+.}-{4:4}:
       __mutex_lock_common+0x1d0/0x2190 kernel/locking/mutex.c:601
       __mutex_lock kernel/locking/mutex.c:746 [inline]
       mutex_lock_nested+0x2c/0x38 kernel/locking/mutex.c:798
       bch2_quota_reservation_add fs/bcachefs/fs-io.h:97 [inline]
       __bch2_folio_reservation_get+0x5c0/0xa00 fs/bcachefs/fs-io-pagecache.c:460
       bch2_folio_reservation_get fs/bcachefs/fs-io-pagecache.c:477 [inline]
       bch2_page_mkwrite+0xa48/0xd60 fs/bcachefs/fs-io-pagecache.c:637
       do_page_mkwrite+0x138/0x2b8 mm/memory.c:3287
       wp_page_shared mm/memory.c:3688 [inline]
       do_wp_page+0x1b54/0x43a8 mm/memory.c:3907
       handle_pte_fault mm/memory.c:6013 [inline]
       __handle_mm_fault mm/memory.c:6140 [inline]
       handle_mm_fault+0x1064/0x4cec mm/memory.c:6309
       do_page_fault+0x428/0x1554 arch/arm64/mm/fault.c:647
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:919
       el0_da+0x64/0x160 arch/arm64/kernel/entry-common.c:627
       el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:789
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

-> #2 (sb_pagefaults#2){.+.+}-{0:0}:
       percpu_down_read include/linux/percpu-rwsem.h:52 [inline]
       __sb_start_write include/linux/fs.h:1783 [inline]
       sb_start_pagefault include/linux/fs.h:1948 [inline]
       bch2_page_mkwrite+0x260/0xd60 fs/bcachefs/fs-io-pagecache.c:614
       do_page_mkwrite+0x138/0x2b8 mm/memory.c:3287
       wp_page_shared mm/memory.c:3688 [inline]
       do_wp_page+0x1b54/0x43a8 mm/memory.c:3907
       handle_pte_fault mm/memory.c:6013 [inline]
       __handle_mm_fault mm/memory.c:6140 [inline]
       handle_mm_fault+0x1064/0x4cec mm/memory.c:6309
       do_page_fault+0x428/0x1554 arch/arm64/mm/fault.c:647
       do_mem_abort+0x70/0x194 arch/arm64/mm/fault.c:919
       el0_da+0x64/0x160 arch/arm64/kernel/entry-common.c:627
       el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:789
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

-> #1 (vm_lock){++++}-{0:0}:
       __vma_enter_locked+0x184/0x354 mm/memory.c:6473
       __vma_start_write+0x34/0x158 mm/memory.c:6497
       vma_start_write include/linux/mm.h:829 [inline]
       vma_expand+0x1b8/0x8f0 mm/vma.c:1086
       relocate_vma_down+0x234/0x400 mm/mmap.c:1767
       setup_arg_pages+0x4b4/0x920 fs/exec.c:800
       load_elf_binary+0x8c4/0x1ebc fs/binfmt_elf.c:1019
       search_binary_handler fs/exec.c:1778 [inline]
       exec_binprm fs/exec.c:1810 [inline]
       bprm_execve+0x77c/0x10dc fs/exec.c:1862
       kernel_execve+0x70c/0x7f4 fs/exec.c:2028
       run_init_process+0x1bc/0x1ec init/main.c:1378
       try_to_run_init_process+0x20/0x7c init/main.c:1385
       kernel_init+0xa8/0x1dc init/main.c:1513
       ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:847

-> #0 (&mm->mmap_lock){++++}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3166 [inline]
       check_prevs_add kernel/locking/lockdep.c:3285 [inline]
       validate_chain kernel/locking/lockdep.c:3909 [inline]
       __lock_acquire+0x1728/0x3058 kernel/locking/lockdep.c:5235
       lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5866
       __might_fault+0xc4/0x124 mm/memory.c:7151
       drm_mode_atomic_ioctl+0x494/0xde4 drivers/gpu/drm/drm_atomic_uapi.c:1458
       drm_ioctl_kernel+0x238/0x310 drivers/gpu/drm/drm_ioctl.c:796
       drm_ioctl+0x65c/0xa5c drivers/gpu/drm/drm_ioctl.c:893
       vfs_ioctl fs/ioctl.c:51 [inline]
       __do_sys_ioctl fs/ioctl.c:906 [inline]
       __se_sys_ioctl fs/ioctl.c:892 [inline]
       __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:892
       __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+0x58/0x17c arch/arm64/kernel/entry-common.c:767
       el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
       el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600

other info that might help us debug this:

Chain exists of:
  &mm->mmap_lock --> crtc_ww_class_acquire --> crtc_ww_class_mutex

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(crtc_ww_class_mutex);
                               lock(crtc_ww_class_acquire);
                               lock(crtc_ww_class_mutex);
  rlock(&mm->mmap_lock);

 *** DEADLOCK ***

2 locks held by syz.1.455/8130:
 #0: ffff80009c4e78f0 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_mode_atomic_ioctl+0x3b0/0xde4 drivers/gpu/drm/drm_atomic_uapi.c:1444
 #1: ffff80009c4e7918 (crtc_ww_class_mutex){+.+.}-{4:4}, at: drm_mode_atomic_ioctl+0x3b0/0xde4 drivers/gpu/drm/drm_atomic_uapi.c:1444

stack backtrace:
CPU: 0 UID: 0 PID: 8130 Comm: syz.1.455 Not tainted 6.15.0-rc5-syzkaller-gc32f8dc5aaf9 #0 PREEMPT 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call trace:
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:466 (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_circular_bug+0x324/0x32c kernel/locking/lockdep.c:2079
 check_noncircular+0x154/0x174 kernel/locking/lockdep.c:2211
 check_prev_add kernel/locking/lockdep.c:3166 [inline]
 check_prevs_add kernel/locking/lockdep.c:3285 [inline]
 validate_chain kernel/locking/lockdep.c:3909 [inline]
 __lock_acquire+0x1728/0x3058 kernel/locking/lockdep.c:5235
 lock_acquire+0x14c/0x2e0 kernel/locking/lockdep.c:5866
 __might_fault+0xc4/0x124 mm/memory.c:7151
 drm_mode_atomic_ioctl+0x494/0xde4 drivers/gpu/drm/drm_atomic_uapi.c:1458
 drm_ioctl_kernel+0x238/0x310 drivers/gpu/drm/drm_ioctl.c:796
 drm_ioctl+0x65c/0xa5c drivers/gpu/drm/drm_ioctl.c:893
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl fs/ioctl.c:892 [inline]
 __arm64_sys_ioctl+0x14c/0x1c4 fs/ioctl.c:892
 __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+0x58/0x17c arch/arm64/kernel/entry-common.c:767
 el0t_64_sync_handler+0x78/0x108 arch/arm64/kernel/entry-common.c:786
 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600