Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 ================================================================== BUG: KCSAN: data-race in data_push_tail / vsnprintf write to 0xffffffff88e4a987 of 32 bytes by task 20681 on cpu 1: vsnprintf+0x2ce/0x890 lib/vsprintf.c:2878 vscnprintf+0x41/0x90 lib/vsprintf.c:2991 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2189 vprintk_store+0x599/0x860 kernel/printk/printk.c:2309 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2448 set_capacity_and_notify+0x14c/0x1f0 block/genhd.c:93 loop_set_size+0x2e/0x70 drivers/block/loop.c:220 loop_configure+0x825/0x9c0 drivers/block/loop.c:1077 lo_ioctl+0x1e1/0x12b0 drivers/block/loop.c:1532 blkdev_ioctl+0x356/0x440 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583 x64_sys_call+0x1816/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffffffff88e4a988 of 8 bytes by task 20685 on cpu 0: data_make_reusable kernel/printk/printk_ringbuffer.c:591 [inline] data_push_tail+0xfd/0x420 kernel/printk/printk_ringbuffer.c:676 data_alloc+0xfb/0x2e0 kernel/printk/printk_ringbuffer.c:1061 prb_reserve+0x807/0xaf0 kernel/printk/printk_ringbuffer.c:1685 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2448 show_opcodes+0xfe/0x120 arch/x86/kernel/dumpstack.c:121 show_iret_regs+0x12/0x40 arch/x86/kernel/dumpstack.c:147 __show_regs+0x2a/0x440 arch/x86/kernel/process_64.c:77 show_regs_if_on_stack arch/x86/kernel/dumpstack.c:165 [inline] show_trace_log_lvl+0x423/0x560 arch/x86/kernel/dumpstack.c:298 __dump_stack+0x1d/0x30 lib/dump_stack.c:94 dump_stack_lvl+0xe8/0x140 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+0x265/0x280 lib/fault-inject.c:174 should_failslab+0x8c/0xb0 mm/failslab.c:46 slab_pre_alloc_hook mm/slub.c:4900 [inline] slab_alloc_node mm/slub.c:5222 [inline] __do_kmalloc_node mm/slub.c:5603 [inline] __kmalloc_noprof+0xa5/0x570 mm/slub.c:5616 kmalloc_noprof include/linux/slab.h:961 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] __register_sysctl_table+0x54/0xc00 fs/proc/proc_sysctl.c:1379 register_pidns_sysctls+0xe0/0x140 kernel/pid.c:776 create_pid_namespace kernel/pid_namespace.c:111 [inline] copy_pid_ns+0x345/0x540 kernel/pid_namespace.c:182 create_new_namespaces+0x176/0x3d0 kernel/nsproxy.c:97 unshare_nsproxy_namespaces+0xe8/0x120 kernel/nsproxy.c:218 ksys_unshare+0x3d0/0x6d0 kernel/fork.c:3129 __do_sys_unshare kernel/fork.c:3200 [inline] __se_sys_unshare kernel/fork.c:3198 [inline] __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3198 x64_sys_call+0x2915/0x3000 arch/x86/include/generated/asm/syscalls_64.h:273 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x0000000100004619 -> 0x2064657463657465 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 20685 Comm: syz.6.15743 Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025 ================================================================== RSP: 002b:00007f364e6ce038 EFLAGS: 00000246 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 00007f364fee6090 RCX: 00007f364fc8eec9 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062040200 RBP: 00007f364e6ce090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007f364fee6128 R14: 00007f364fee6090 R15: 00007fff891f8d48 ---------------- Code disassembly (best guess), 1 bytes skipped: 0: ff c3 inc %ebx 2: 66 2e 0f 1f 84 00 00 cs nopw 0x0(%rax,%rax,1) 9: 00 00 00 c: 0f 1f 40 00 nopl 0x0(%rax) 10: 48 89 f8 mov %rdi,%rax 13: 48 89 f7 mov %rsi,%rdi 16: 48 89 d6 mov %rdx,%rsi 19: 48 89 ca mov %rcx,%rdx 1c: 4d 89 c2 mov %r8,%r10 1f: 4d 89 c8 mov %r9,%r8 22: 4c 8b 4c 24 08 mov 0x8(%rsp),%r9 27: 0f 05 syscall * 29: 48 3d 01 f0 ff ff cmp $0xfffffffffffff001,%rax <-- trapping instruction 2f: 73 01 jae 0x32 31: c3 ret 32: 48 c7 c1 a8 ff ff ff mov $0xffffffffffffffa8,%rcx 39: f7 d8 neg %eax 3b: 64 89 01 mov %eax,%fs:(%rcx) 3e: 48 rex.W