Code: ec 28 48 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 99 93 02 00 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 ef 93 02 00 48 RSP: 002b:00007fdd0afc1030 EFLAGS: 00000246 ORIG_RAX: 0000000000000000 RAX: ffffffffffffffda RBX: 00007fdd0cb75fa0 RCX: 00007fdd0c95bb7c RDX: 000000000000000f RSI: 00007fdd0afc10a0 RDI: 0000000000000004 RBP: 00007fdd0afc1090 R08: 0000000000000000 R09: 0000000000000000 ================================================================== BUG: KCSAN: data-race in data_alloc / data_push_tail write to 0xffffffff88bece50 of 8 bytes by task 20653 on cpu 0: data_alloc+0x216/0x2c0 kernel/printk/printk_ringbuffer.c:1082 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326 vprintk_emit+0x168/0x690 kernel/printk/printk.c:2408 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x7a/0xa0 kernel/printk/printk.c:2457 __ext4_msg+0x134/0x1a0 fs/ext4/super.c:1000 ext4_parse_param+0x839/0xf40 fs/ext4/super.c:2192 vfs_parse_fs_param+0x13b/0x290 fs/fs_context.c:146 vfs_parse_fs_string fs/fs_context.c:188 [inline] vfs_parse_monolithic_sep+0x19b/0x220 fs/fs_context.c:230 generic_parse_monolithic+0x24/0x30 fs/fs_context.c:258 parse_monolithic_mount_data+0x43/0x50 fs/fs_context.c:719 do_new_mount+0x1fa/0x690 fs/namespace.c:3556 path_mount+0x49b/0xb30 fs/namespace.c:3887 do_mount fs/namespace.c:3900 [inline] __do_sys_mount fs/namespace.c:4111 [inline] __se_sys_mount+0x27f/0x2d0 fs/namespace.c:4088 __x64_sys_mount+0x67/0x80 fs/namespace.c:4088 x64_sys_call+0x2c84/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:166 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffffffff88bece50 of 8 bytes by task 20651 on cpu 1: data_make_reusable kernel/printk/printk_ringbuffer.c:594 [inline] data_push_tail+0x102/0x430 kernel/printk/printk_ringbuffer.c:679 data_alloc+0xbe/0x2c0 kernel/printk/printk_ringbuffer.c:1054 prb_reserve+0x85e/0xb60 kernel/printk/printk_ringbuffer.c:1669 vprintk_store+0x558/0x870 kernel/printk/printk.c:2326 vprintk_emit+0x168/0x690 kernel/printk/printk.c:2408 vprintk_default+0x26/0x30 kernel/printk/printk.c:2447 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x7a/0xa0 kernel/printk/printk.c:2457 __show_regs+0xbc/0x450 arch/x86/kernel/process_64.c:87 show_trace_log_lvl+0x348/0x400 arch/x86/kernel/dumpstack.c:301 __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0xf2/0x150 lib/dump_stack.c:120 dump_stack+0x15/0x1a lib/dump_stack.c:129 fail_dump lib/fault-inject.c:73 [inline] should_fail_ex+0x24a/0x260 lib/fault-inject.c:174 should_fail+0xb/0x10 lib/fault-inject.c:184 should_fail_usercopy+0x1a/0x20 lib/fault-inject-usercopy.c:37 _inline_copy_to_user include/linux/uaccess.h:193 [inline] _copy_to_user+0x20/0xa0 lib/usercopy.c:26 copy_to_user include/linux/uaccess.h:225 [inline] simple_read_from_buffer+0xa0/0x110 fs/libfs.c:1121 proc_fail_nth_read+0xf9/0x140 fs/proc/base.c:1482 vfs_read+0x19b/0x6f0 fs/read_write.c:563 ksys_read+0xe8/0x1b0 fs/read_write.c:708 __do_sys_read fs/read_write.c:717 [inline] __se_sys_read fs/read_write.c:715 [inline] __x64_sys_read+0x42/0x50 fs/read_write.c:715 x64_sys_call+0x2874/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:1 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f value changed: 0x00000000fffffcd0 -> 0x0000000100000885 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 20651 Comm: syz.1.3395 Not tainted 6.14.0-rc5-syzkaller-00214-g21e4543a2e2f #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 ================================================================== R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 0000000000000000 R14: 00007fdd0cb75fa0 R15: 00007ffe3e6c8e38 ---------------- Code disassembly (best guess): 0: ec in (%dx),%al 1: 28 48 89 sub %cl,-0x77(%rax) 4: 54 push %rsp 5: 24 18 and $0x18,%al 7: 48 89 74 24 10 mov %rsi,0x10(%rsp) c: 89 7c 24 08 mov %edi,0x8(%rsp) 10: e8 99 93 02 00 call 0x293ae 15: 48 8b 54 24 18 mov 0x18(%rsp),%rdx 1a: 48 8b 74 24 10 mov 0x10(%rsp),%rsi 1f: 41 89 c0 mov %eax,%r8d 22: 8b 7c 24 08 mov 0x8(%rsp),%edi 26: 31 c0 xor %eax,%eax 28: 0f 05 syscall * 2a: 48 3d 00 f0 ff ff cmp $0xfffffffffffff000,%rax <-- trapping instruction 30: 77 34 ja 0x66 32: 44 89 c7 mov %r8d,%edi 35: 48 89 44 24 08 mov %rax,0x8(%rsp) 3a: e8 ef 93 02 00 call 0x2942e 3f: 48 rex.W