==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff866666f0 of 8 bytes by task 13939 on cpu 0:
 data_alloc+0x291/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:86
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __ext4_msg+0x134/0x1a0 fs/ext4/super.c:1000
 ext4_parse_param+0x839/0xf40 fs/ext4/super.c:2194
 vfs_parse_fs_param+0x13b/0x290 fs/fs_context.c:146
 vfs_parse_fs_string fs/fs_context.c:188 [inline]
 vfs_parse_monolithic_sep fs/fs_context.c:230 [inline]
 generic_parse_monolithic+0x165/0x1d0 fs/fs_context.c:258
 parse_monolithic_mount_data+0x43/0x50 fs/fs_context.c:719
 do_new_mount+0x1fa/0x690 fs/namespace.c:3503
 path_mount+0x49b/0xb30 fs/namespace.c:3834
 do_mount fs/namespace.c:3847 [inline]
 __do_sys_mount fs/namespace.c:4057 [inline]
 __se_sys_mount+0x27c/0x2d0 fs/namespace.c:4034
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4034
 x64_sys_call+0x2c84/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff866666f0 of 8 bytes by task 13935 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+0x235/0xb60 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326
 vprintk_emit+0x15e/0x680 kernel/printk/printk.c:2408
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447
 vprintk+0x75/0x80 kernel/printk/printk_safe.c:86
 _printk+0x7a/0xa0 kernel/printk/printk.c:2457
 __netdev_printk+0x2d1/0x3e0 net/core/dev.c:11946
 netdev_info+0x99/0xc0 net/core/dev.c:11993
 __dev_set_promiscuity+0x165/0x340 net/core/dev.c:8738
 __dev_change_flags+0x1ed/0x410 net/core/dev.c:8958
 dev_change_flags+0x59/0xd0 net/core/dev.c:9021
 do_setlink+0x6ca/0x22c0 net/core/rtnetlink.c:3109
 rtnl_setlink+0x2c9/0x3a0 net/core/rtnetlink.c:3421
 rtnetlink_rcv_msg+0x651/0x710 net/core/rtnetlink.c:6921
 netlink_rcv_skb+0x12c/0x230 net/netlink/af_netlink.c:2542
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6948
 netlink_unicast_kernel net/netlink/af_netlink.c:1321 [inline]
 netlink_unicast+0x599/0x670 net/netlink/af_netlink.c:1347
 netlink_sendmsg+0x5cc/0x6e0 net/netlink/af_netlink.c:1891
 sock_sendmsg_nosec net/socket.c:711 [inline]
 __sock_sendmsg+0x140/0x180 net/socket.c:726
 sock_write_iter+0x15e/0x1a0 net/socket.c:1147
 do_iter_readv_writev+0x394/0x450
 vfs_writev+0x2d4/0x880 fs/read_write.c:1050
 do_writev+0xf4/0x220 fs/read_write.c:1096
 __do_sys_writev fs/read_write.c:1164 [inline]
 __se_sys_writev fs/read_write.c:1161 [inline]
 __x64_sys_writev+0x45/0x50 fs/read_write.c:1161
 x64_sys_call+0x1fab/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:21
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffffc7280 -> 0x0000000000074308

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13935 Comm: syz.3.3140 Not tainted 6.13.0-rc3-syzkaller-00017-gf44d154d6e3d #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/25/2024
==================================================================
sit0: entered promiscuous mode
netlink: 'syz.3.3140': attribute type 1 has an invalid length.
netlink: 1 bytes leftover after parsing attributes in process `syz.3.3140'.