EXT4-fs (loop1): feature flags set on rev 0 fs, running e2fsck is recommended
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff868819f8 of 8 bytes by task 17377 on cpu 0:
 data_alloc+0x27d/0x2b0 kernel/printk/printk_ringbuffer.c:1096
 prb_reserve+0x808/0xaf0 kernel/printk/printk_ringbuffer.c:1669
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 bio_check_eod block/blk-core.c:563 [inline]
 submit_bio_noacct+0x808/0x8f0 block/blk-core.c:796
 submit_bio+0x227/0x240 block/blk-core.c:916
 mpage_bio_submit_read fs/mpage.c:75 [inline]
 do_mpage_readpage+0x132/0xe20 fs/mpage.c:312
 mpage_readahead+0x1b7/0x2e0 fs/mpage.c:371
 fat_readahead+0x1c/0x30 fs/fat/inode.c:209
 read_pages+0xa0/0x480 mm/readahead.c:160
 page_cache_ra_unbounded+0x347/0x380 mm/readahead.c:297
 do_page_cache_ra mm/readahead.c:327 [inline]
 page_cache_ra_order+0x102/0x120 mm/readahead.c:532
 do_sync_mmap_readahead+0x249/0x280 mm/filemap.c:3262
 filemap_fault+0x311/0xb40 mm/filemap.c:3403
 __do_fault+0xb9/0x200 mm/memory.c:5098
 do_shared_fault mm/memory.c:5582 [inline]
 do_fault mm/memory.c:5656 [inline]
 do_pte_missing mm/memory.c:4160 [inline]
 handle_pte_fault mm/memory.c:5997 [inline]
 __handle_mm_fault mm/memory.c:6140 [inline]
 handle_mm_fault+0xeff/0x2ae0 mm/memory.c:6309
 do_user_addr_fault+0x636/0x1090 arch/x86/mm/fault.c:1337
 handle_page_fault arch/x86/mm/fault.c:1480 [inline]
 exc_page_fault+0x54/0xc0 arch/x86/mm/fault.c:1538
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623

read to 0xffffffff868819f8 of 8 bytes by task 17383 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+0x221/0xaf0 kernel/printk/printk_ringbuffer.c:1619
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2326
 vprintk_emit+0x178/0x650 kernel/printk/printk.c:2426
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2465
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2475
 __ext4_msg+0x18f/0x1a0 fs/ext4/super.c:985
 ext4_check_feature_compatibility+0x470/0x5f0 fs/ext4/super.c:4687
 __ext4_fill_super fs/ext4/super.c:5325 [inline]
 ext4_fill_super+0x1ade/0x34e0 fs/ext4/super.c:5726
 get_tree_bdev_flags+0x28e/0x300 fs/super.c:1636
 get_tree_bdev+0x1f/0x30 fs/super.c:1659
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5758
 vfs_get_tree+0x54/0x1d0 fs/super.c:1759
 do_new_mount+0x207/0x680 fs/namespace.c:3884
 path_mount+0x4a4/0xb20 fs/namespace.c:4211
 do_mount fs/namespace.c:4224 [inline]
 __do_sys_mount fs/namespace.c:4435 [inline]
 __se_sys_mount+0x28f/0x2e0 fs/namespace.c:4412
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4412
 x64_sys_call+0xd36/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000015768 -> 0x00000000000b0890

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17383 Comm: syz.1.4654 Not tainted 6.15.0-rc5-syzkaller-00136-g9c69f8884904 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
==================================================================
EXT4-fs (loop1): mounting ext2 file system using the ext4 subsystem
[EXT4 FS bs=4096, gc=1, bpg=32768, ipg=32, mo=a042c01c, mo2=0002]
System zones: 0-2, 18-18, 34-34
EXT4-fs warning (device loop1): ext4_update_dynamic_rev:1132: updating to rev 1 because of new feature flag, running e2fsck is recommended
EXT4-fs (loop1): 1 truncate cleaned up
EXT4-fs (loop1): mounted filesystem 00000000-0000-0000-0000-000000000000 r/w without journal. Quota mode: none.