==================================================================
BUG: KCSAN: data-race in data_push_tail / number

write to 0xffffffff8416a3e8 of 1 bytes by task 18803 on cpu 0:
 number+0x6eb/0xb50 lib/vsprintf.c:543
 vsnprintf+0xb6d/0xed0 lib/vsprintf.c:2863
 vscnprintf+0x29/0x80 lib/vsprintf.c:2900
 printk_sprint kernel/printk/printk.c:2012 [inline]
 vprintk_store+0x4c1/0x9c0 kernel/printk/printk.c:2115
 vprintk_emit+0xca/0x3d0 kernel/printk/printk.c:2157
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2185
 vprintk+0x15a/0x170 kernel/printk/printk_safe.c:392
 printk+0x62/0x87 kernel/printk/printk.c:2216
 __show_regs+0x63/0x330 arch/x86/kernel/process_64.c:81
 show_regs_if_on_stack arch/x86/kernel/dumpstack.c:173 [inline]
 show_trace_log_lvl+0x548/0x600 arch/x86/kernel/dumpstack.c:298
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xb7/0x103 lib/dump_stack.c:105
 dump_stack+0x11/0x1a lib/dump_stack.c:112
 fail_dump lib/fault-inject.c:52 [inline]
 should_fail+0x23c/0x250 lib/fault-inject.c:146
 __should_failslab+0x81/0x90 mm/failslab.c:33
 should_failslab+0x5/0x20 mm/slab_common.c:1326
 slab_pre_alloc_hook mm/slab.h:494 [inline]
 slab_alloc mm/slab.c:3306 [inline]
 __do_kmalloc mm/slab.c:3700 [inline]
 __kmalloc+0x66/0x340 mm/slab.c:3711
 kmalloc_array include/linux/slab.h:631 [inline]
 kcalloc+0x32/0x50 include/linux/slab.h:660
 ext4_find_extent+0x21c/0x7f0 fs/ext4/extents.c:864
 ext4_ext_map_blocks+0xd9/0x1f00 fs/ext4/extents.c:4061
 ext4_map_blocks+0x1be/0xef0 fs/ext4/inode.c:563
 ext4_getblk+0xb1/0x3d0 fs/ext4/inode.c:848
 ext4_bread+0x28/0x100 fs/ext4/inode.c:900
 ext4_append+0xd1/0x1c0 fs/ext4/namei.c:67
 ext4_init_new_dir+0x177/0x500 fs/ext4/namei.c:2885
 ext4_mkdir+0x329/0x760 fs/ext4/namei.c:2931
 vfs_mkdir+0x2a4/0x370 fs/namei.c:3823
 do_mkdirat+0x11d/0x200 fs/namei.c:3848
 __do_sys_mkdir fs/namei.c:3866 [inline]
 __se_sys_mkdir fs/namei.c:3864 [inline]
 __x64_sys_mkdir+0x32/0x40 fs/namei.c:3864
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffffffff8416a3e8 of 8 bytes by task 18826 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:587 [inline]
 data_push_tail+0x125/0x460 kernel/printk/printk_ringbuffer.c:672
 data_alloc+0xbc/0x2b0 kernel/printk/printk_ringbuffer.c:1043
 prb_reserve+0x8f0/0xbc0 kernel/printk/printk_ringbuffer.c:1549
 vprintk_store+0x3e9/0x9c0 kernel/printk/printk.c:2105
 vprintk_emit+0xca/0x3d0 kernel/printk/printk.c:2157
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2185
 vprintk+0x15a/0x170 kernel/printk/printk_safe.c:392
 printk+0x62/0x87 kernel/printk/printk.c:2216
 __nla_validate_parse+0x148e/0x17f0 lib/nlattr.c:600
 __nla_parse+0x3c/0x50 lib/nlattr.c:685
 __nlmsg_parse include/net/netlink.h:733 [inline]
 genl_family_rcv_msg_attrs_parse+0x148/0x1a0 net/netlink/genetlink.c:548
 genl_family_rcv_msg_doit net/netlink/genetlink.c:717 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:783 [inline]
 genl_rcv_msg+0x5aa/0x800 net/netlink/genetlink.c:800
 netlink_rcv_skb+0x13e/0x240 net/netlink/af_netlink.c:2504
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:811
 netlink_unicast_kernel net/netlink/af_netlink.c:1314 [inline]
 netlink_unicast+0x5ec/0x6b0 net/netlink/af_netlink.c:1340
 netlink_sendmsg+0x6d9/0x7c0 net/netlink/af_netlink.c:1929
 sock_sendmsg_nosec net/socket.c:703 [inline]
 sock_sendmsg net/socket.c:723 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2392
 ___sys_sendmsg net/socket.c:2446 [inline]
 __sys_sendmsg+0x1ed/0x270 net/socket.c:2475
 __do_sys_sendmsg net/socket.c:2484 [inline]
 __se_sys_sendmsg net/socket.c:2482 [inline]
 __x64_sys_sendmsg+0x42/0x50 net/socket.c:2482
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000100006dda -> 0x3030303032303030

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18826 Comm: syz-executor.0 Not tainted 5.14.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================