FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
CPU: 0 UID: 0 PID: 23764 Comm: syz.0.5836 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
==================================================================
BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86a94920 of 8 bytes by task 23767 on cpu 1:
 data_alloc+0x310/0x390 kernel/printk/printk_ringbuffer.c:1129
 prb_reserve+0x8d7/0xae0 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2302
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 set_capacity_and_notify+0x1dd/0x230 block/genhd.c:93
 loop_set_size+0x2e/0x70 drivers/block/loop.c:220
 loop_configure+0x828/0x9c0 drivers/block/loop.c:1080
 lo_ioctl+0x1e1/0x13a0 drivers/block/loop.c:1555
 blkdev_ioctl+0x387/0x460 block/ioctl.c:792
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583
 x64_sys_call+0x14b0/0x3000 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86a94920 of 16 bytes by task 23764 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1931 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1979 [inline]
 _prb_read_valid+0x1bc/0x950 kernel/printk/printk_ringbuffer.c:2170
 desc_update_last_finalized+0x8f/0x170 kernel/printk/printk_ringbuffer.c:1570
 prb_final_commit+0x10d/0x150 kernel/printk/printk_ringbuffer.c:1839
 vprintk_store+0x88b/0x910 kernel/printk/printk.c:2328
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 dump_stack_print_info+0x182/0x1b0 lib/dump_stack.c:68
 __dump_stack+0x11/0x30 lib/dump_stack.c:93
 dump_stack_lvl+0x95/0xd0 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+0x263/0x280 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4906 [inline]
 slab_alloc_node mm/slub.c:5239 [inline]
 kmem_cache_alloc_noprof+0x68/0x490 mm/slub.c:5270
 skb_clone+0x151/0x1f0 net/core/skbuff.c:2088
 __netlink_deliver_tap_skb net/netlink/af_netlink.c:300 [inline]
 __netlink_deliver_tap+0x2c9/0x500 net/netlink/af_netlink.c:325
 netlink_deliver_tap net/netlink/af_netlink.c:338 [inline]
 __netlink_sendskb net/netlink/af_netlink.c:1260 [inline]
 netlink_sendskb+0x126/0x150 net/netlink/af_netlink.c:1269
 netlink_unicast+0x2a2/0x690 net/netlink/af_netlink.c:1359
 nlmsg_unicast include/net/netlink.h:1198 [inline]
 netlink_ack+0x4c8/0x500 net/netlink/af_netlink.c:2512
 netlink_rcv_skb+0x192/0x220 net/netlink/af_netlink.c:2556
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6985
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x5c8/0x6f0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x5af/0x600 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
 x64_sys_call+0x17ba/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 23764 Comm: syz.0.5836 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 __dump_stack+0x1d/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x95/0xd0 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+0x263/0x280 lib/fault-inject.c:174
 should_failslab+0x8c/0xb0 mm/failslab.c:46
 slab_pre_alloc_hook mm/slub.c:4906 [inline]
 slab_alloc_node mm/slub.c:5239 [inline]
 kmem_cache_alloc_noprof+0x68/0x490 mm/slub.c:5270
 skb_clone+0x151/0x1f0 net/core/skbuff.c:2088
 __netlink_deliver_tap_skb net/netlink/af_netlink.c:300 [inline]
 __netlink_deliver_tap+0x2c9/0x500 net/netlink/af_netlink.c:325
 netlink_deliver_tap net/netlink/af_netlink.c:338 [inline]
 __netlink_sendskb net/netlink/af_netlink.c:1260 [inline]
 netlink_sendskb+0x126/0x150 net/netlink/af_netlink.c:1269
 netlink_unicast+0x2a2/0x690 net/netlink/af_netlink.c:1359
 nlmsg_unicast include/net/netlink.h:1198 [inline]
 netlink_ack+0x4c8/0x500 net/netlink/af_netlink.c:2512
 netlink_rcv_skb+0x192/0x220 net/netlink/af_netlink.c:2556
 rtnetlink_rcv+0x1c/0x30 net/core/rtnetlink.c:6985
 netlink_unicast_kernel net/netlink/af_netlink.c:1318 [inline]
 netlink_unicast+0x5c0/0x690 net/netlink/af_netlink.c:1344
 netlink_sendmsg+0x5c8/0x6f0 net/netlink/af_netlink.c:1894
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg net/socket.c:742 [inline]
 ____sys_sendmsg+0x5af/0x600 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmsg net/socket.c:2678 [inline]
 __do_sys_sendmsg net/socket.c:2683 [inline]
 __se_sys_sendmsg net/socket.c:2681 [inline]
 __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2681
 x64_sys_call+0x17ba/0x3000 arch/x86/include/generated/asm/syscalls_64.h:47
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fd565a6aeb9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd5644c7028 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fd565ce5fa0 RCX: 00007fd565a6aeb9
RDX: 0000000020044000 RSI: 0000200000000b00 RDI: 0000000000000003
RBP: 00007fd5644c7090 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fd565ce6038 R14: 00007fd565ce5fa0 R15: 00007ffd85b4d4e8
 </TASK>