BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff86c6a488 of 8 bytes by task 29152 on cpu 1: data_alloc+0x308/0x380 kernel/printk/printk_ringbuffer.c:1130 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2504 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline] __show_trace_log_lvl+0x460/0x560 arch/x86/kernel/dumpstack.c:282 __dump_stack+0x1d/0x30 lib/dump_stack.c:94 dump_stack_lvl+0x95/0xd0 lib/dump_stack.c:120 dump_stack+0x15/0x1b lib/dump_stack.c:129 fail_dump lib/fault-inject.c:73 [inline] should_fail_ex+0x25e/0x270 lib/fault-inject.c:174 should_failslab+0x8c/0xb0 mm/failslab.c:46 slab_pre_alloc_hook mm/slub.c:4567 [inline] slab_alloc_node mm/slub.c:4925 [inline] __kmalloc_cache_node_noprof+0x81/0x3e0 mm/slub.c:5530 _kmalloc_node_noprof include/linux/slab.h:1174 [inline] __get_vm_area_node+0x106/0x1d0 mm/vmalloc.c:3215 __vmalloc_node_range_noprof+0x266/0x11e0 mm/vmalloc.c:4042 __vmalloc_node_noprof mm/vmalloc.c:4143 [inline] __vmalloc_noprof+0xa4/0xf0 mm/vmalloc.c:4159 bpf_prog_alloc_no_stats+0x47/0x390 kernel/bpf/core.c:106 bpf_prog_alloc+0x3c/0x150 kernel/bpf/core.c:155 bpf_prog_load+0x54b/0x1100 kernel/bpf/syscall.c:3097 __sys_bpf+0xbae/0xc30 kernel/bpf/syscall.c:6418 __do_sys_bpf kernel/bpf/syscall.c:6537 [inline] __se_sys_bpf kernel/bpf/syscall.c:6534 [inline] __x64_sys_bpf+0x69/0x80 kernel/bpf/syscall.c:6534 x64_sys_call+0x10cb/0x3020 arch/x86/include/generated/asm/syscalls_64.h:322 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffffffff86c6a488 of 8 bytes by task 68 on cpu 0: desc_read kernel/printk/printk_ringbuffer.c:496 [inline] desc_push_tail kernel/printk/printk_ringbuffer.c:792 [inline] desc_reserve kernel/printk/printk_ringbuffer.c:938 [inline] prb_reserve+0x21a/0xaf0 kernel/printk/printk_ringbuffer.c:1677 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2504 __ext4_grp_locked_error+0x56a/0x7a0 fs/ext4/super.c:1067 ext4_mb_generate_buddy+0x3ae/0x470 fs/ext4/mballoc.c:1314 ext4_mb_init_cache+0x88e/0xbc0 fs/ext4/mballoc.c:1499 ext4_mb_init_group+0x3d6/0x580 fs/ext4/mballoc.c:1638 ext4_mb_good_group_nolock fs/ext4/mballoc.c:2833 [inline] ext4_mb_scan_group+0x5e5/0xf50 fs/ext4/mballoc.c:2970 ext4_mb_scan_groups_linear fs/ext4/mballoc.c:1176 [inline] ext4_mb_scan_groups fs/ext4/mballoc.c:1208 [inline] ext4_mb_regular_allocator+0x5bc/0x1550 fs/ext4/mballoc.c:3062 ext4_mb_new_blocks+0x7c7/0x1e70 fs/ext4/mballoc.c:6310 ext4_ext_map_blocks+0xde9/0x2f30 fs/ext4/extents.c:4461 ext4_map_create_blocks+0xd1/0x390 fs/ext4/inode.c:631 ext4_map_blocks+0x57f/0x950 fs/ext4/inode.c:824 mpage_map_one_extent fs/ext4/inode.c:2397 [inline] mpage_map_and_submit_extent fs/ext4/inode.c:2491 [inline] ext4_do_writepages+0x161d/0x2720 fs/ext4/inode.c:2949 ext4_writepages+0x18f/0x300 fs/ext4/inode.c:3043 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571 __writeback_single_inode+0x7b/0x660 fs/fs-writeback.c:1787 writeback_sb_inodes+0x4d9/0xaa0 fs/fs-writeback.c:2079 wb_writeback+0x20c/0x510 fs/fs-writeback.c:2264 wb_do_writeback fs/fs-writeback.c:2432 [inline] wb_workfn+0x1a4/0xa50 fs/fs-writeback.c:2477 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405 worker_thread+0x569/0x750 kernel/workqueue.c:3486 kthread+0x221/0x270 kernel/kthread.c:436 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 value changed: 0x000000000008cda8 -> 0x0000000000147ac8 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 68 Comm: kworker/u8:4 Tainted: G W syzkaller #0 PREEMPT(lazy) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 Workqueue: writeback wb_workfn (flush-7:3) ================================================================== EXT4-fs error (device loop3): ext4_mb_generate_buddy:1317: group 0, block bitmap and bg descriptor inconsistent: 25 vs 150994969 free clusters EXT4-fs (loop3): Delayed block allocation failed for inode 18 at logical offset 0 with max blocks 2 with error 28 EXT4-fs (loop3): This should not happen!! Data will be lost EXT4-fs (loop3): Total free blocks count 0 EXT4-fs (loop3): Free/Dirty block details EXT4-fs (loop3): free_blocks=2415919104 EXT4-fs (loop3): dirty_blocks=16 EXT4-fs (loop3): Block reservation details EXT4-fs (loop3): i_reserved_data_blocks=1