Call Trace: __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 ================================================================== BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff868683a0 of 8 bytes by task 12701 on cpu 0: data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2475 set_capacity_and_notify+0x14c/0x1f0 block/genhd.c:93 loop_set_size+0x2e/0x70 drivers/block/loop.c:210 loop_configure+0x8d3/0xa50 drivers/block/loop.c:1067 lo_ioctl+0x1e1/0x1350 drivers/block/loop.c:1523 blkdev_ioctl+0x352/0x440 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:584 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:584 x64_sys_call+0x1816/0x2ff0 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 0xffffffff868683a0 of 8 bytes by task 12700 on cpu 1: desc_read kernel/printk/printk_ringbuffer.c:482 [inline] desc_push_tail kernel/printk/printk_ringbuffer.c:778 [inline] desc_reserve kernel/printk/printk_ringbuffer.c:924 [inline] prb_reserve+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2475 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline] show_trace_log_lvl+0x4e3/0x560 arch/x86/kernel/dumpstack.c:282 __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:4132 [inline] slab_alloc_node mm/slub.c:4208 [inline] __do_kmalloc_node mm/slub.c:4363 [inline] __kmalloc_node_track_caller_noprof+0xa4/0x410 mm/slub.c:4383 __kmemdup_nul mm/util.c:63 [inline] kstrdup+0x3e/0xd0 mm/util.c:83 kstrdup_const+0x3e/0x50 mm/util.c:103 alloc_vfsmnt+0xe7/0x300 fs/namespace.c:360 clone_mnt+0x46/0x630 fs/namespace.c:1305 copy_tree+0x2cd/0x8c0 fs/namespace.c:2260 copy_mnt_ns+0x120/0x5c0 fs/namespace.c:4231 create_new_namespaces+0x83/0x3d0 kernel/nsproxy.c:78 unshare_nsproxy_namespaces+0xe8/0x120 kernel/nsproxy.c:218 ksys_unshare+0x3d0/0x6d0 kernel/fork.c:3121 __do_sys_unshare kernel/fork.c:3192 [inline] __se_sys_unshare kernel/fork.c:3190 [inline] __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3190 x64_sys_call+0x2911/0x2ff0 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: 0xfffffffffffc1358 -> 0x0000000000060ff0 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 12700 Comm: syz.0.3310 Not tainted 6.16.0-syzkaller-08685-g260f6f4fda93 #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 ================================================================== 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:4132 [inline] slab_alloc_node mm/slub.c:4208 [inline] __do_kmalloc_node mm/slub.c:4363 [inline] __kmalloc_node_track_caller_noprof+0xa4/0x410 mm/slub.c:4383 __kmemdup_nul mm/util.c:63 [inline] kstrdup+0x3e/0xd0 mm/util.c:83 kstrdup_const+0x3e/0x50 mm/util.c:103 alloc_vfsmnt+0xe7/0x300 fs/namespace.c:360 clone_mnt+0x46/0x630 fs/namespace.c:1305 copy_tree+0x2cd/0x8c0 fs/namespace.c:2260 copy_mnt_ns+0x120/0x5c0 fs/namespace.c:4231 create_new_namespaces+0x83/0x3d0 kernel/nsproxy.c:78 unshare_nsproxy_namespaces+0xe8/0x120 kernel/nsproxy.c:218 ksys_unshare+0x3d0/0x6d0 kernel/fork.c:3121 __do_sys_unshare kernel/fork.c:3192 [inline] __se_sys_unshare kernel/fork.c:3190 [inline] __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3190 x64_sys_call+0x2911/0x2ff0 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 RIP: 0033:0x7f6608b5eb69 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 RSP: 002b:00007f66071bf038 EFLAGS: 00000246 ORIG_RAX: 0000000000000110 RAX: ffffffffffffffda RBX: 00007f6608d85fa0 RCX: 00007f6608b5eb69 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000002c020400 RBP: 00007f66071bf090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002 R13: 0000000000000000 R14: 00007f6608d85fa0 R15: 00007ffd67f3aaf8