copy_from_iter include/linux/uio.h:228 [inline] copy_from_iter_full include/linux/uio.h:245 [inline] memcpy_from_msg include/linux/skbuff.h:4272 [inline] netlink_sendmsg+0x471/0x6b0 net/netlink/af_netlink.c:1881 ================================================================== BUG: KCSAN: data-race in data_alloc / prb_reserve write to 0xffffffff8687ee90 of 8 bytes by task 16773 on cpu 0: data_alloc+0x280/0x2e0 kernel/printk/printk_ringbuffer.c:1102 prb_reserve+0x807/0xaf0 kernel/printk/printk_ringbuffer.c:1685 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2448 bio_check_eod block/blk-core.c:565 [inline] submit_bio_noacct+0x8c8/0x9a0 block/blk-core.c:801 submit_bio+0x2a6/0x2c0 block/blk-core.c:921 submit_bh_wbc+0x2e0/0x320 fs/buffer.c:2824 __block_write_full_folio+0x5ab/0x8f0 fs/buffer.c:1933 block_write_full_folio+0x2c2/0x2e0 fs/buffer.c:-1 mpage_write_folio fs/mpage.c:641 [inline] mpage_writepages+0x6cf/0x1250 fs/mpage.c:670 fat_writepages+0x24/0x30 fs/fat/inode.c:199 do_writepages+0x1c6/0x310 mm/page-writeback.c:2604 filemap_fdatawrite_wbc mm/filemap.c:389 [inline] __filemap_fdatawrite_range mm/filemap.c:422 [inline] __filemap_fdatawrite mm/filemap.c:428 [inline] filemap_fdatawrite+0xec/0x120 mm/filemap.c:433 writeback_inode fs/fat/inode.c:1872 [inline] fat_flush_inodes+0xcc/0x150 fs/fat/inode.c:1890 fat_truncate_blocks+0x4d8/0x550 fs/fat/file.c:395 fat_write_failed fs/fat/inode.c:218 [inline] fat_write_end+0xba/0x160 fs/fat/inode.c:246 generic_perform_write+0x312/0x490 mm/filemap.c:4263 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4359 generic_file_write_iter+0x8d/0x2f0 mm/filemap.c:4385 new_sync_write fs/read_write.c:593 [inline] vfs_write+0x52a/0x960 fs/read_write.c:686 ksys_write+0xda/0x1a0 fs/read_write.c:738 __do_sys_write fs/read_write.c:749 [inline] __se_sys_write fs/read_write.c:746 [inline] __x64_sys_write+0x40/0x50 fs/read_write.c:746 x64_sys_call+0x2802/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2 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 0xffffffff8687ee90 of 8 bytes by task 16787 on cpu 1: desc_read kernel/printk/printk_ringbuffer.c:479 [inline] desc_push_tail kernel/printk/printk_ringbuffer.c:775 [inline] desc_reserve kernel/printk/printk_ringbuffer.c:921 [inline] prb_reserve+0x220/0xaf0 kernel/printk/printk_ringbuffer.c:1635 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82 _printk+0x79/0xa0 kernel/printk/printk.c:2448 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:35 copy_from_user_iter lib/iov_iter.c:50 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] __copy_from_iter lib/iov_iter.c:249 [inline] _copy_from_iter+0xd2/0xe80 lib/iov_iter.c:260 copy_from_iter include/linux/uio.h:228 [inline] copy_from_iter_full include/linux/uio.h:245 [inline] memcpy_from_msg include/linux/skbuff.h:4272 [inline] netlink_sendmsg+0x471/0x6b0 net/netlink/af_netlink.c:1881 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x145/0x180 net/socket.c:742 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2630 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2684 __sys_sendmsg net/socket.c:2716 [inline] __do_sys_sendmsg net/socket.c:2721 [inline] __se_sys_sendmsg net/socket.c:2719 [inline] __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2719 x64_sys_call+0x191e/0x3000 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: 0x0000000000008d88 -> 0x00000000000b40c8 Reported by Kernel Concurrency Sanitizer on: CPU: 1 UID: 0 PID: 16787 Comm: syz.6.4425 Tainted: G W syzkaller #0 PREEMPT(voluntary) Tainted: [W]=WARN Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025 ================================================================== sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x145/0x180 net/socket.c:742 ____sys_sendmsg+0x31e/0x4e0 net/socket.c:2630 ___sys_sendmsg+0x17b/0x1d0 net/socket.c:2684 __sys_sendmsg net/socket.c:2716 [inline] __do_sys_sendmsg net/socket.c:2721 [inline] __se_sys_sendmsg net/socket.c:2719 [inline] __x64_sys_sendmsg+0xd4/0x160 net/socket.c:2719 x64_sys_call+0x191e/0x3000 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: 0033:0x7f6b0704f6c9 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:00007f6b05aaf038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f6b072a5fa0 RCX: 00007f6b0704f6c9 RDX: 0000000000008000 RSI: 00002000000005c0 RDI: 000000000000000a RBP: 00007f6b05aaf090 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001 R13: 00007f6b072a6038 R14: 00007f6b072a5fa0 R15: 00007ffeba59e6d8