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

write to 0xffffffff8709db28 of 1 bytes by task 23907 on cpu 1:
 string_nocheck lib/vsprintf.c:647 [inline]
 string+0x17b/0x220 lib/vsprintf.c:725
 vsnprintf+0xb57/0xe80 lib/vsprintf.c:2782
 vscnprintf+0x3e/0x80 lib/vsprintf.c:2888
 printk_sprint kernel/printk/printk.c:2092 [inline]
 vprintk_store+0x5f2/0xb50 kernel/printk/printk.c:2206
 vprintk_emit+0xcc/0x430 kernel/printk/printk.c:2252
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2282
 vprintk+0x7f/0x90 kernel/printk/printk_safe.c:50
 _printk+0x76/0x96 kernel/printk/printk.c:2292
 dump_stack_print_info+0x122/0x130 lib/dump_stack.c:66
 __dump_stack lib/dump_stack.c:87 [inline]
 dump_stack_lvl+0xca/0x122 lib/dump_stack.c:106
 dump_stack+0x11/0x12 lib/dump_stack.c:113
 fail_dump lib/fault-inject.c:55 [inline]
 should_fail+0x242/0x250 lib/fault-inject.c:149
 should_fail_usercopy+0x16/0x20 lib/fault-inject-usercopy.c:37
 copyin+0x1a/0x90 lib/iov_iter.c:177
 _copy_from_iter+0x256/0x8b0 lib/iov_iter.c:628
 copy_from_iter include/linux/uio.h:184 [inline]
 copy_from_iter_full include/linux/uio.h:191 [inline]
 memcpy_from_msg include/linux/skbuff.h:3959 [inline]
 netlink_sendmsg+0x53d/0x760 net/netlink/af_netlink.c:1906
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg net/socket.c:734 [inline]
 ____sys_sendmsg+0x38f/0x500 net/socket.c:2482
 ___sys_sendmsg net/socket.c:2536 [inline]
 __sys_sendmsg+0x19a/0x230 net/socket.c:2565
 __do_sys_sendmsg net/socket.c:2574 [inline]
 __se_sys_sendmsg net/socket.c:2572 [inline]
 __x64_sys_sendmsg+0x42/0x50 net/socket.c:2572
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffffffff8709db28 of 8 bytes by task 23914 on cpu 0:
 data_make_reusable kernel/printk/printk_ringbuffer.c:590 [inline]
 data_push_tail+0x10f/0x440 kernel/printk/printk_ringbuffer.c:675
 data_alloc+0xbc/0x2b0 kernel/printk/printk_ringbuffer.c:1046
 prb_reserve+0x897/0xbd0 kernel/printk/printk_ringbuffer.c:1555
 vprintk_store+0x51c/0xb50 kernel/printk/printk.c:2196
 vprintk_emit+0xcc/0x430 kernel/printk/printk.c:2252
 vprintk_default+0x22/0x30 kernel/printk/printk.c:2282
 vprintk+0x7f/0x90 kernel/printk/printk_safe.c:50
 _printk+0x76/0x96 kernel/printk/printk.c:2292
 fail_dump lib/fault-inject.c:48 [inline]
 should_fail+0x229/0x250 lib/fault-inject.c:149
 should_fail_usercopy+0x16/0x20 lib/fault-inject-usercopy.c:37
 _copy_to_user+0x1a/0x90 lib/usercopy.c:29
 copy_to_user include/linux/uaccess.h:160 [inline]
 simple_read_from_buffer+0xab/0x120 fs/libfs.c:768
 proc_fail_nth_read+0x10d/0x150 fs/proc/base.c:1425
 vfs_read+0x198/0x560 fs/read_write.c:468
 ksys_read+0xe8/0x1a0 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000100007018 -> 0x6f4720656c676f6f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 23914 Comm: syz-executor.0 Not tainted 6.0.0-rc5-syzkaller-00017-gd1221cea11fc-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
==================================================================
CPU: 0 PID: 23914 Comm: syz-executor.0 Not tainted 6.0.0-rc5-syzkaller-00017-gd1221cea11fc-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xd6/0x122 lib/dump_stack.c:106
 dump_stack+0x11/0x12 lib/dump_stack.c:113
 fail_dump lib/fault-inject.c:55 [inline]
 should_fail+0x242/0x250 lib/fault-inject.c:149
 should_fail_usercopy+0x16/0x20 lib/fault-inject-usercopy.c:37
 _copy_to_user+0x1a/0x90 lib/usercopy.c:29
 copy_to_user include/linux/uaccess.h:160 [inline]
 simple_read_from_buffer+0xab/0x120 fs/libfs.c:768
 proc_fail_nth_read+0x10d/0x150 fs/proc/base.c:1425
 vfs_read+0x198/0x560 fs/read_write.c:468
 ksys_read+0xe8/0x1a0 fs/read_write.c:607
 __do_sys_read fs/read_write.c:617 [inline]
 __se_sys_read fs/read_write.c:615 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:615
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fe5b78f4f7c
Code: ec 28 48 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 f9 fc ff ff 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 34 44 89 c7 48 89 44 24 08 e8 2f fd ff ff 48
RSP: 002b:00007fe5b70b8160 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007fe5b7a54f80 RCX: 00007fe5b78f4f7c
RDX: 000000000000000f RSI: 00007fe5b70b81e0 RDI: 0000000000000005
RBP: 00007fe5b70b81d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000002
R13: 00007ffdb8e7db0f R14: 00007fe5b70b8300 R15: 0000000000022000
 </TASK>