loop3: detected capacity change from 0 to 1024
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86c807f0 of 8 bytes by task 9753 on cpu 1:
 data_alloc+0x31c/0x390 kernel/printk/printk_ringbuffer.c:1130
 prb_reserve+0x8d7/0xae0 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __nla_validate_parse+0x1735/0x1cf0 lib/nlattr.c:647
 __nla_parse+0x40/0x60 lib/nlattr.c:732
 nla_parse_nested_deprecated include/net/netlink.h:1379 [inline]
 rtnl_newlink+0x785/0x1330 net/core/rtnetlink.c:4019
 rtnetlink_rcv_msg+0x64b/0x720 net/core/rtnetlink.c:6958
 netlink_rcv_skb+0x123/0x220 net/netlink/af_netlink.c:2550
 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+0x563/0x5b0 net/socket.c:2592
 ___sys_sendmsg+0x195/0x1e0 net/socket.c:2646
 __sys_sendmmsg+0x185/0x320 net/socket.c:2735
 __do_sys_sendmmsg net/socket.c:2762 [inline]
 __se_sys_sendmmsg net/socket.c:2759 [inline]
 __x64_sys_sendmmsg+0x57/0x70 net/socket.c:2759
 x64_sys_call+0x27aa/0x3020 arch/x86/include/generated/asm/syscalls_64.h:308
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c807f0 of 8 bytes by task 9755 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:496 [inline]
 desc_push_tail kernel/printk/printk_ringbuffer.c:792 [inline]
 desc_reserve kernel/printk/printk_ringbuffer.c:938 [inline]
 prb_reserve+0x207/0xae0 kernel/printk/printk_ringbuffer.c:1674
 vprintk_store+0x54a/0x910 kernel/printk/printk.c:2354
 vprintk_emit+0x1a4/0x600 kernel/printk/printk.c:2455
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2494
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2504
 __ext4_msg+0x1aa/0x1c0 fs/ext4/super.c:995
 ext4_feature_set_ok+0x15d/0x1e0 fs/ext4/super.c:3617
 ext4_check_feature_compatibility+0x1e4/0x5f0 fs/ext4/super.c:4749
 __ext4_fill_super fs/ext4/super.c:5384 [inline]
 ext4_fill_super+0x1d22/0x37c0 fs/ext4/super.c:5791
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1694
 get_tree_bdev+0x1f/0x30 fs/super.c:1717
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5823
 vfs_get_tree+0x57/0x1d0 fs/super.c:1754
 fc_mount fs/namespace.c:1193 [inline]
 do_new_mount_fc fs/namespace.c:3763 [inline]
 do_new_mount+0x288/0x8d0 fs/namespace.c:3839
 path_mount+0x4d0/0xbc0 fs/namespace.c:4159
 do_mount fs/namespace.c:4172 [inline]
 __do_sys_mount fs/namespace.c:4361 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4338
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4338
 x64_sys_call+0x2d61/0x3020 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000b97e8 -> 0x0000000000169d90

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 9755 Comm: syz.3.7855 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================
EXT4-fs (loop3): filesystem is read-only
EXT4-fs (loop3): ext4_check_descriptors: Inode table for group 0 overlaps block group descriptors
EXT4-fs (loop3): ext4_check_descriptors: Checksum for group 0 failed (11891!=20869)
EXT4-fs (loop3): stripe (65535) is not aligned with cluster size (16), stripe is disabled
EXT4-fs error (device loop3): ext4_get_journal_inode:5863: comm syz.3.7855: inode #1: comm syz.3.7855: iget: illegal inode #
loop3: lost filesystem error report for type 5 error -117
EXT4-fs (loop3): no journal found
EXT4-fs (loop3): can't get journal size
EXT4-fs error (device loop3): __ext4_fill_super:5563: inode #2: comm syz.3.7855: iget: special inode unallocated
loop3: lost file I/O error report for ino 2 type 5 pos 0x0 len 0x0 error -117
EXT4-fs (loop3): get root inode failed
EXT4-fs (loop3): mount failed