syz.3.3375: attempt to access beyond end of device
loop3: rw=2049, sector=680, nr_sectors = 8 limit=512
==================================================================
BUG: KCSAN: data-race in data_push_tail / vsnprintf

write to 0xffffffff893a4687 of 41 bytes by task 4752 on cpu 0:
 vsnprintf+0x2c0/0x8c0 lib/vsprintf.c:2896
 vscnprintf+0x41/0x90 lib/vsprintf.c:3014
 printk_sprint+0x30/0x2b0 kernel/printk/printk.c:2222
 vprintk_store+0x57b/0x910 kernel/printk/printk.c:2364
 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
 bio_check_eod block/blk-core.c:609 [inline]
 submit_bio_noacct+0x85f/0x920 block/blk-core.c:843
 submit_bio+0x2a4/0x2c0 block/blk-core.c:962
 mpage_bio_submit_write fs/mpage.c:82 [inline]
 __mpage_writepages+0x12d6/0x1370 fs/mpage.c:689
 mpage_writepages include/linux/mpage.h:27 [inline]
 fat_writepages+0x26/0x30 fs/fat/inode.c:200
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 __writeback_single_inode+0x7b/0x660 fs/fs-writeback.c:1787
 writeback_sb_inodes+0x4d9/0xaa0 fs/fs-writeback.c:2079
 __writeback_inodes_wb+0x8a/0x180 fs/fs-writeback.c:2155
 wb_writeback+0x21e/0x510 fs/fs-writeback.c:2266
 wb_check_start_all fs/fs-writeback.c:2392 [inline]
 wb_do_writeback fs/fs-writeback.c:2439 [inline]
 wb_workfn+0x4f4/0xa50 fs/fs-writeback.c:2477
 process_one_work kernel/workqueue.c:3322 [inline]
 process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405
 worker_thread+0x569/0x750 kernel/workqueue.c:3486
 kthread+0x221/0x270 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff893a4688 of 8 bytes by task 17887 on cpu 1:
 data_make_reusable kernel/printk/printk_ringbuffer.c:608 [inline]
 data_push_tail+0x104/0x440 kernel/printk/printk_ringbuffer.c:693
 data_alloc+0x111/0x380 kernel/printk/printk_ringbuffer.c:1089
 prb_reserve+0x8e3/0xaf0 kernel/printk/printk_ringbuffer.c:1727
 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
 bio_check_eod block/blk-core.c:609 [inline]
 submit_bio_noacct+0x85f/0x920 block/blk-core.c:843
 submit_bio+0x2a4/0x2c0 block/blk-core.c:962
 mpage_bio_submit_write fs/mpage.c:82 [inline]
 mpage_write_folio fs/mpage.c:593 [inline]
 __mpage_writepages+0x946/0x1370 fs/mpage.c:686
 mpage_writepages include/linux/mpage.h:27 [inline]
 fat_writepages+0x26/0x30 fs/fat/inode.c:200
 do_writepages+0x1b9/0x300 mm/page-writeback.c:2571
 filemap_writeback mm/filemap.c:387 [inline]
 filemap_fdatawrite_range mm/filemap.c:412 [inline]
 filemap_write_and_wait_range+0x166/0x370 mm/filemap.c:684
 kiocb_write_and_wait mm/filemap.c:2904 [inline]
 generic_file_read_iter+0xf4/0x320 mm/filemap.c:2978
 do_iter_readv_writev+0x4f6/0x5a0 fs/read_write.c:-1
 vfs_readv+0x1e8/0x6d0 fs/read_write.c:1019
 do_preadv fs/read_write.c:1133 [inline]
 __do_sys_preadv2 fs/read_write.c:1192 [inline]
 __se_sys_preadv2+0xfc/0x1c0 fs/read_write.c:1183
 __x64_sys_preadv2+0x67/0x80 fs/read_write.c:1183
 x64_sys_call+0x2b3b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:328
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000d32 -> 0x742074706d657474

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 17887 Comm: syz.3.3375 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================
syz.3.3375: attempt to access beyond end of device
loop3: rw=2049, sector=720, nr_sectors = 32 limit=512
syz.3.3375: attempt to access beyond end of device
loop3: rw=2049, sector=784, nr_sectors = 32 limit=512
syz.3.3375: attempt to access beyond end of device
loop3: rw=2049, sector=848, nr_sectors = 32 limit=512