CPU: 0 UID: 0 PID: 15412 Comm: syz.6.2396 Not tainted 6.16.0-rc2-syzkaller-00269-g11313e2f7812 #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 Call Trace: __dump_stack+0x1d/0x30 lib/dump_stack.c:94 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_fail+0xb/0x20 lib/fault-inject.c:184 ================================================================== BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff86872d88 of 8 bytes by task 15411 on cpu 1: 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 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:1068 lo_ioctl+0x559/0x15d0 drivers/block/loop.c:-1 blkdev_ioctl+0x34f/0x440 block/ioctl.c:704 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:907 [inline] __se_sys_ioctl+0xce/0x140 fs/ioctl.c:893 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893 x64_sys_call+0x19a8/0x2fb0 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 read to 0xffffffff86872d88 of 8 bytes by task 15412 on cpu 0: 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 printk_stack_address arch/x86/kernel/dumpstack.c:70 [inline] show_trace_log_lvl+0x4e3/0x560 arch/x86/kernel/dumpstack.c:282 __dump_stack+0x1d/0x30 lib/dump_stack.c:94 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_fail+0xb/0x20 lib/fault-inject.c:184 should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37 _inline_copy_from_user include/linux/uaccess.h:163 [inline] _copy_from_user+0x1c/0xb0 lib/usercopy.c:18 copy_from_user include/linux/uaccess.h:212 [inline] copy_msghdr_from_user net/socket.c:2496 [inline] sendmsg_copy_msghdr net/socket.c:2597 [inline] ___sys_sendmsg+0xc1/0x1d0 net/socket.c:2616 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2655 x64_sys_call+0x2999/0x2fb0 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 value changed: 0xfffffffffffdcc90 -> 0x00000000000771f8 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 15412 Comm: syz.6.2396 Not tainted 6.16.0-rc2-syzkaller-00269-g11313e2f7812 #0 PREEMPT(voluntary) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025 ================================================================== should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37 _inline_copy_from_user include/linux/uaccess.h:163 [inline] _copy_from_user+0x1c/0xb0 lib/usercopy.c:18 copy_from_user include/linux/uaccess.h:212 [inline] copy_msghdr_from_user net/socket.c:2496 [inline] sendmsg_copy_msghdr net/socket.c:2597 [inline] ___sys_sendmsg+0xc1/0x1d0 net/socket.c:2616 __sys_sendmsg net/socket.c:2652 [inline] __do_sys_sendmsg net/socket.c:2657 [inline] __se_sys_sendmsg net/socket.c:2655 [inline] __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2655 x64_sys_call+0x2999/0x2fb0 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 RIP: 0033:0x7ffbd2c0e929 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffbd1277038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007ffbd2e35fa0 RCX: 00007ffbd2c0e929 RDX: 0000000000000000 RSI: 0000200000000240 RDI: 0000000000000005 RBP: 00007ffbd1277090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000000000 R14: 00007ffbd2e35fa0 R15: 00007fff1ef73ed8