==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff8687c8c0 of 8 bytes by task 22098 on cpu 0:
 data_alloc+0x290/0x2c0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x86a/0xb80 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7f/0xb0 kernel/printk/printk.c:2475
 set_capacity_and_notify+0x155/0x200 block/genhd.c:93
 loop_set_size+0x2e/0x70 drivers/block/loop.c:210
 loop_configure+0x89c/0xa30 drivers/block/loop.c:1044
 lo_ioctl+0x5fa/0x15e0 drivers/block/loop.c:-1
 blkdev_ioctl+0x35b/0x450 block/ioctl.c:698
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x168d/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8687c8c0 of 8 bytes by task 22097 on cpu 1:
 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+0x239/0xb80 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x552/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x1a0/0x6c0 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x7f/0xb0 kernel/printk/printk.c:2475
 __ext4_error_inode+0x2e7/0x410 fs/ext4/super.c:848
 ext4_do_update_inode fs/ext4/inode.c:5211 [inline]
 ext4_mark_iloc_dirty+0x383/0xdb0 fs/ext4/inode.c:5869
 __ext4_mark_inode_dirty+0x320/0x440 fs/ext4/inode.c:6074
 ext4_dirty_inode+0x91/0xb0 fs/ext4/inode.c:6103
 __mark_inode_dirty+0x166/0x7e0 fs/fs-writeback.c:2527
 mark_inode_dirty_sync include/linux/fs.h:2550 [inline]
 dquot_free_space include/linux/quotaops.h:380 [inline]
 dquot_free_block include/linux/quotaops.h:390 [inline]
 ext4_xattr_release_block+0x520/0x580 fs/ext4/xattr.c:1344
 ext4_xattr_delete_inode+0x6fe/0x7a0 fs/ext4/xattr.c:2984
 ext4_evict_inode+0xa9f/0xdf0 fs/ext4/inode.c:276
 evict+0x2de/0x550 fs/inode.c:810
 iput_final fs/inode.c:1898 [inline]
 iput+0x42a/0x5b0 fs/inode.c:1924
 ext4_ext_migrate+0x92a/0x9b0 fs/ext4/migrate.c:588
 __ext4_ioctl fs/ext4/ioctl.c:1402 [inline]
 ext4_ioctl+0xfa9/0x2e60 fs/ext4/ioctl.c:1620
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0xc9/0x140 fs/ioctl.c:892
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:892
 x64_sys_call+0x168d/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000006230 -> 0x00000000000b5140

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22097 Comm: syz.5.5972 Tainted: G        W           6.15.0-rc3-syzkaller-00032-ga79be02bba5c #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================
EXT4-fs error (device loop5): ext4_do_update_inode:5211: inode #19: comm syz.5.5972: corrupted inode contents
EXT4-fs (loop5): Remounting filesystem read-only
EXT4-fs warning (device loop5): ext4_evict_inode:279: xattr delete (err -30)