syzbot

Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 __dump_stack+0x1d/0x30 lib/dump_stack.c:94
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff8936a3d0 of 26 bytes by task 20677 on cpu 1:
 vsnprintf+0x2ce/0x860 lib/vsprintf.c:2892
 vscnprintf+0x41/0x90 lib/vsprintf.c:3006
 printk_sprint+0x30/0x2b0 kernel/printk/printk.c:2222
 vprintk_store+0x57b/0x910 kernel/printk/printk.c:2364
 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_warning_inode+0x184/0x1a0 fs/ext4/super.c:1043
 dx_probe+0x720/0x990 fs/ext4/namei.c:-1
 ext4_dx_find_entry fs/ext4/namei.c:1721 [inline]
 __ext4_find_entry+0x35d/0xe00 fs/ext4/namei.c:1561
 ext4_lookup_entry fs/ext4/namei.c:1703 [inline]
 ext4_lookup+0xcd/0x3a0 fs/ext4/namei.c:1769
 lookup_one_qstr_excl+0xc7/0x240 fs/namei.c:1810
 __start_dirop fs/namei.c:2920 [inline]
 start_dirop fs/namei.c:2942 [inline]
 filename_create+0x155/0x220 fs/namei.c:4951
 filename_mkdirat+0x81/0x300 fs/namei.c:5298
 __do_sys_mkdirat fs/namei.c:5326 [inline]
 __se_sys_mkdirat+0x32/0xf0 fs/namei.c:5323
 __x64_sys_mkdirat+0x43/0x50 fs/namei.c:5323
 x64_sys_call+0x2c4e/0x3020 arch/x86/include/generated/asm/syscalls_64.h:259
 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 0xffffffff8936a3d8 of 8 bytes by task 20673 on cpu 0:
 data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
 data_push_tail+0x104/0x440 kernel/printk/printk_ringbuffer.c:693
 data_alloc+0x111/0x380 kernel/printk/printk_ringbuffer.c:1089
 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
 dump_header+0x80/0x240 mm/oom_kill.c:464
 oom_kill_process+0x295/0x350 mm/oom_kill.c:1031
 out_of_memory+0x981/0xbc0 mm/oom_kill.c:1169
 mem_cgroup_out_of_memory mm/memcontrol.c:1907 [inline]
 mem_cgroup_oom mm/memcontrol.c:1930 [inline]
 try_charge_memcg+0x621/0xa00 mm/memcontrol.c:2672
 obj_cgroup_charge_pages mm/memcontrol.c:3072 [inline]
 __memcg_kmem_charge_page+0x199/0x3a0 mm/memcontrol.c:3116
 __alloc_frozen_pages_noprof+0x18a/0x350 mm/page_alloc.c:5238
 alloc_pages_mpol+0xa9/0x1d0 mm/mempolicy.c:2490
 alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
 alloc_pages_noprof+0x8f/0x140 mm/mempolicy.c:2581
 vm_area_alloc_pages mm/vmalloc.c:3728 [inline]
 __vmalloc_area_node mm/vmalloc.c:3878 [inline]
 __vmalloc_node_range_noprof+0xae9/0x11e0 mm/vmalloc.c:4064
 __kvmalloc_node_noprof+0x3d4/0x640 mm/slub.c:6861
 futex_hash_allocate+0x192/0x920 kernel/futex/core.c:1823
 futex_hash_prctl+0xd8/0xf0 kernel/futex/core.c:1995
 __do_sys_prctl kernel/sys.c:2885 [inline]
 __se_sys_prctl+0x4f4/0x13c0 kernel/sys.c:2534
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2534
 x64_sys_call+0x2533/0x3020 arch/x86/include/generated/asm/syscalls_64.h:158
 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

value changed: 0x0000000000000f28 -> 0x20676e696e726177

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 20673 Comm: syz.1.4336 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
 dump_stack_lvl+0x95/0xd0 lib/dump_stack.c:120
 dump_stack+0x15/0x1b lib/dump_stack.c:129
 dump_header+0x80/0x240 mm/oom_kill.c:464
 oom_kill_process+0x295/0x350 mm/oom_kill.c:1031
 out_of_memory+0x981/0xbc0 mm/oom_kill.c:1169
 mem_cgroup_out_of_memory mm/memcontrol.c:1907 [inline]
 mem_cgroup_oom mm/memcontrol.c:1930 [inline]
 try_charge_memcg+0x621/0xa00 mm/memcontrol.c:2672
 obj_cgroup_charge_pages mm/memcontrol.c:3072 [inline]
 __memcg_kmem_charge_page+0x199/0x3a0 mm/memcontrol.c:3116
 __alloc_frozen_pages_noprof+0x18a/0x350 mm/page_alloc.c:5238
 alloc_pages_mpol+0xa9/0x1d0 mm/mempolicy.c:2490
 alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline]
 alloc_pages_noprof+0x8f/0x140 mm/mempolicy.c:2581
 vm_area_alloc_pages mm/vmalloc.c:3728 [inline]
 __vmalloc_area_node mm/vmalloc.c:3878 [inline]
 __vmalloc_node_range_noprof+0xae9/0x11e0 mm/vmalloc.c:4064
 __kvmalloc_node_noprof+0x3d4/0x640 mm/slub.c:6861
 futex_hash_allocate+0x192/0x920 kernel/futex/core.c:1823
 futex_hash_prctl+0xd8/0xf0 kernel/futex/core.c:1995
 __do_sys_prctl kernel/sys.c:2885 [inline]
 __se_sys_prctl+0x4f4/0x13c0 kernel/sys.c:2534
 __x64_sys_prctl+0x67/0x80 kernel/sys.c:2534
 x64_sys_call+0x2533/0x3020 arch/x86/include/generated/asm/syscalls_64.h:158
 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
RIP: 0033:0x7f233b53ce59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2339f97028 EFLAGS: 00000246 ORIG_RAX: 000000000000009d
RAX: ffffffffffffffda RBX: 00007f233b7b5fa0 RCX: 00007f233b53ce59
RDX: 0000000001000000 RSI: 0000000000000001 RDI: 000000000000004e
RBP: 00007f233b5d2d6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f233b7b6038 R14: 00007f233b7b5fa0 R15: 00007fffc62c3338
 </TASK>
memory: usage 307200kB, limit 307200kB, failcnt 661
memory+swap: usage 373596kB, limit 9007199254740988kB, failcnt 0
kmem: usage 273412kB, limit 9007199254740988kB, failcnt 0
Memory cgroup stats for /syz1:
cache 524288
rss 32768
shmem 0
mapped_file 0
dirty 0
writeback 0
workingset_refault_anon 1658
workingset_refault_file 4544
swap 67956736
swapcached 89522176
pgpgin 908159
pgpgout 908013
pgfault 960122
pgmajfault 69
inactive_anon 28672
active_anon 45056
inactive_file 0
active_file 524288
unevictable 0
hierarchical_memory_limit 314572800
hierarchical_memsw_limit 9223372036854771712
total_cache 524288
total_rss 32768
total_shmem 0
total_mapped_file 0
total_dirty 0
total_writeback 0
total_workingset_refault_anon 1658
total_workingset_refault_file 4544
total_swap 67956736
total_swapcached 89522176
total_pgpgin 908159
total_pgpgout 908013
total_pgfault 960122
total_pgmajfault 69
total_inactive_anon 28672
total_active_anon 45056
total_inactive_file 0
total_active_file 524288
total_unevictable 0
oom-kill:constraint=CONSTRAINT_MEMCG,nodemask=(null),cpuset=/,mems_allowed=0,oom_memcg=/syz1,task_memcg=/syz1,task=syz.1.4336,pid=20671,uid=0
Memory cgroup out of memory: Killed process 20673 (syz.1.4336) total-vm:94168kB, anon-rss:1344kB, file-rss:22356kB, shmem-rss:0kB, UID:0 pgtables:128kB oom_score_adj:1000