loop6: detected capacity change from 0 to 512
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff8686bf50 of 8 bytes by task 19845 on cpu 0:
 data_alloc+0x31c/0x390 kernel/printk/printk_ringbuffer.c:1130
 prb_reserve+0x8d7/0xad0 kernel/printk/printk_ringbuffer.c:1724
 vprintk_store+0x53c/0x830 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x5c0 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 __ext4_error_inode+0x2ca/0x3f0 fs/ext4/super.c:853
 ext4_do_update_inode fs/ext4/inode.c:5617 [inline]
 ext4_mark_iloc_dirty+0x35e/0xda0 fs/ext4/inode.c:6267
 __ext4_mark_inode_dirty+0x2e2/0x3f0 fs/ext4/inode.c:6473
 ext4_xattr_delete_inode+0x71e/0x790 fs/ext4/xattr.c:3000
 ext4_evict_inode+0xa20/0xd40 fs/ext4/inode.c:270
 evict+0x2af/0x510 fs/inode.c:837
 iput_final fs/inode.c:1954 [inline]
 iput+0x4bd/0x650 fs/inode.c:2006
 ext4_process_orphan+0x1a9/0x1c0 fs/ext4/orphan.c:358
 ext4_orphan_cleanup+0x6a8/0xa00 fs/ext4/orphan.c:472
 __ext4_fill_super fs/ext4/super.c:5658 [inline]
 ext4_fill_super+0x3411/0x37a0 fs/ext4/super.c:5777
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1691
 get_tree_bdev+0x1f/0x30 fs/super.c:1714
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5809
 vfs_get_tree+0x57/0x1d0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x24d/0x6a0 fs/namespace.c:3712
 path_mount+0x4ab/0xb80 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8686bf50 of 8 bytes by task 19861 on cpu 1:
 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+0x207/0xad0 kernel/printk/printk_ringbuffer.c:1674
 vprintk_store+0x53c/0x830 kernel/printk/printk.c:2302
 vprintk_emit+0x15a/0x5c0 kernel/printk/printk.c:2402
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2441
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2451
 _fat_msg+0xa4/0xd0 fs/fat/misc.c:62
 fat_fill_super+0x17cd/0x1ce0 fs/fat/inode.c:1695
 msdos_fill_super+0x24/0x30 fs/fat/namei_msdos.c:655
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1691
 get_tree_bdev+0x1f/0x30 fs/super.c:1714
 msdos_get_tree+0x1c/0x30 fs/fat/namei_msdos.c:660
 vfs_get_tree+0x57/0x1d0 fs/super.c:1751
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x24d/0x6a0 fs/namespace.c:3712
 path_mount+0x4ab/0xb80 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xfffffffffffcb020 -> 0x000000000007b348

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 19861 Comm: syz.6.5028 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
FAT-fs (loop6): Invalid FSINFO signature: 0x41615252, 0x05417272 (sector = 1)
FAT-fs (loop6): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
bio_check_eod: 422 callbacks suppressed
syz.6.5028: attempt to access beyond end of device
loop6: rw=8390659, sector=268440016, nr_sectors = 16128 limit=512