CPU: 1 UID: 0 PID: 13706 Comm: +}[@ Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 ================================================================== BUG: KCSAN: data-race in data_push_tail / vsnprintf write to 0xffffffff88e291f7 of 32 bytes by task 13708 on cpu 0: vsnprintf+0x2ce/0x890 lib/vsprintf.c:2878 vscnprintf+0x41/0x90 lib/vsprintf.c:2991 printk_sprint+0x30/0x2d0 kernel/printk/printk.c:2216 vprintk_store+0x599/0x860 kernel/printk/printk.c:2336 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:220 loop_configure+0x825/0x9c0 drivers/block/loop.c:1077 lo_ioctl+0x1e1/0x12b0 drivers/block/loop.c:1532 blkdev_ioctl+0x34f/0x440 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl+0xce/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 0xffffffff88e29210 of 8 bytes by task 13706 on cpu 1: data_make_reusable kernel/printk/printk_ringbuffer.c:594 [inline] data_push_tail+0xfd/0x420 kernel/printk/printk_ringbuffer.c:679 data_alloc+0xbf/0x2b0 kernel/printk/printk_ringbuffer.c:1054 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 dump_stack_print_info+0x1a0/0x1b0 lib/dump_stack.c:71 __dump_stack+0x11/0x30 lib/dump_stack.c:93 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_fail+0xb/0x20 lib/fault-inject.c:184 should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37 copy_from_user_iter lib/iov_iter.c:50 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] __copy_from_iter lib/iov_iter.c:249 [inline] _copy_from_iter+0xd2/0xe80 lib/iov_iter.c:260 copy_from_iter include/linux/uio.h:228 [inline] copy_from_iter_full include/linux/uio.h:245 [inline] memcpy_from_msg include/linux/skbuff.h:4222 [inline] netlink_sendmsg+0x471/0x6b0 net/netlink/af_netlink.c:1881 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg+0x145/0x180 net/socket.c:729 ____sys_sendmsg+0x345/0x4e0 net/socket.c:2614 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2668 __sys_sendmmsg+0x178/0x300 net/socket.c:2757 __do_sys_sendmmsg net/socket.c:2784 [inline] __se_sys_sendmmsg net/socket.c:2781 [inline] __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2781 x64_sys_call+0x1c4a/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:308 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: 0x0000000100004288 -> 0x742030206d6f7266 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 13706 Comm: +}[@ Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 ================================================================== 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 fail_dump lib/fault-inject.c:73 [inline] should_fail_ex+0x265/0x280 lib/fault-inject.c:174 should_fail+0xb/0x20 lib/fault-inject.c:184 should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37 copy_from_user_iter lib/iov_iter.c:50 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] __copy_from_iter lib/iov_iter.c:249 [inline] _copy_from_iter+0xd2/0xe80 lib/iov_iter.c:260 copy_from_iter include/linux/uio.h:228 [inline] copy_from_iter_full include/linux/uio.h:245 [inline] memcpy_from_msg include/linux/skbuff.h:4222 [inline] netlink_sendmsg+0x471/0x6b0 net/netlink/af_netlink.c:1881 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg+0x145/0x180 net/socket.c:729 ____sys_sendmsg+0x345/0x4e0 net/socket.c:2614 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2668 __sys_sendmmsg+0x178/0x300 net/socket.c:2757 __do_sys_sendmmsg net/socket.c:2784 [inline] __se_sys_sendmmsg net/socket.c:2781 [inline] __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2781 x64_sys_call+0x1c4a/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:308 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: 0033:0x7ffac8efeba9 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:00007ffac7967038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 RAX: ffffffffffffffda RBX: 00007ffac9145fa0 RCX: 00007ffac8efeba9 RDX: 04000000000001f2 RSI: 0000200000000000 RDI: 0000000000000005 RBP: 00007ffac7967090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007ffac9146038 R14: 00007ffac9145fa0 R15: 00007ffc5d0fdd98