syzbot

random: crng reseeded on system resumption
loop5: detected capacity change from 0 to 512
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BUG: KCSAN: data-race in data_push_tail / string

write to 0xffffffff88e51500 of 1 bytes by task 29290 on cpu 1:
 string_nocheck lib/vsprintf.c:643 [inline]
 string+0x187/0x220 lib/vsprintf.c:721
 vsnprintf+0x532/0x890 lib/vsprintf.c:2874
 vscnprintf+0x41/0x90 lib/vsprintf.c:2939
 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
 dev_vprintk_emit+0x242/0x2a0 drivers/base/core.c:4917
 dev_printk_emit+0x84/0xb0 drivers/base/core.c:4928
 __netdev_printk+0x35c/0x3e0 net/core/dev.c:12509
 netdev_info+0x9b/0xd0 net/core/dev.c:12564
 netif_change_name+0x628/0x6b0 net/core/dev.c:1466
 do_setlink+0x80b/0x2810 net/core/rtnetlink.c:3121
 rtnl_changelink net/core/rtnetlink.c:3759 [inline]
 __rtnl_newlink net/core/rtnetlink.c:3918 [inline]
 rtnl_newlink+0xe75/0x12d0 net/core/rtnetlink.c:4055
 rtnetlink_rcv_msg+0x5fe/0x6d0 net/core/rtnetlink.c:6944
 netlink_rcv_skb+0x120/0x220 net/netlink/af_netlink.c:2534
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6971
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x5a1/0x670 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x58b/0x6b0 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x142/0x180 net/socket.c:727
 __sys_sendto+0x268/0x330 net/socket.c:2180
 __do_sys_sendto net/socket.c:2187 [inline]
 __se_sys_sendto net/socket.c:2183 [inline]
 __x64_sys_sendto+0x76/0x90 net/socket.c:2183
 x64_sys_call+0x2eb6/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:45
 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 0xffffffff88e51500 of 8 bytes by task 29440 on cpu 0:
 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
 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:1068
 lo_ioctl+0x559/0x15d0 drivers/block/loop.c:-1
 blkdev_ioctl+0x352/0x440 block/ioctl.c:704
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:893
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
 x64_sys_call+0x19a8/0x2fb0 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

value changed: 0x0000000100000fe1 -> 0x697376656474656e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 29440 Comm: syz.5.5978 Not tainted 6.15.0-syzkaller-13804-g939f15e640f1 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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