BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff868830f8 of 8 bytes by task 22447 on cpu 0: data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096 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 dump_stack_print_info+0x1a0/0x1b0 lib/dump_stack.c:71 __dump_stack+0x11/0x30 lib/dump_stack.c:93 dump_stack_lvl+0xe8/0x140 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+0x265/0x280 lib/fault-inject.c:174 should_failslab+0x8c/0xb0 mm/failslab.c:46 slab_pre_alloc_hook mm/slub.c:4133 [inline] slab_alloc_node mm/slub.c:4209 [inline] kmem_cache_alloc_node_noprof+0x57/0x320 mm/slub.c:4281 __alloc_skb+0x101/0x320 net/core/skbuff.c:659 alloc_skb include/linux/skbuff.h:1336 [inline] netlink_alloc_large_skb+0xba/0xf0 net/netlink/af_netlink.c:1186 netlink_sendmsg+0x3cf/0x6b0 net/netlink/af_netlink.c:1871 sock_sendmsg_nosec net/socket.c:714 [inline] __sock_sendmsg+0x142/0x180 net/socket.c:729 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2614 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2668 __sys_sendmsg net/socket.c:2700 [inline] __do_sys_sendmsg net/socket.c:2705 [inline] __se_sys_sendmsg net/socket.c:2703 [inline] __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2703 x64_sys_call+0x191e/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:47 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 0xffffffff868830f8 of 8 bytes by task 22437 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+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619 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:1067 lo_ioctl+0x1e1/0x1350 drivers/block/loop.c:1523 blkdev_ioctl+0x352/0x440 block/ioctl.c:705 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:598 [inline] __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:584 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:584 x64_sys_call+0x1816/0x2ff0 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: 0x00000000000bf0d8 -> 0x00000000001602c0 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 22437 Comm: syz.5.6487 Not tainted 6.17.0-rc1-syzkaller-00214-g99bade344cfa #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 ================================================================== loop5: detected capacity change from 0 to 32768 loop5: p1 p2 p3 < p5 p6 > loop5: p2 size 16775168 extends beyond EOD, truncated loop5: p5 start 4294970168 is beyond EOD, truncated