loop2: rw=2049, sector=146, nr_sectors = 6 limit=128 syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=150, nr_sectors = 2 limit=128 ================================================================== BUG: KCSAN: data-race in data_push_tail / vsnprintf write to 0xffffffff893ca374 of 21 bytes by task 21175 on cpu 1: 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 blk_add_partition block/partitions/core.c:551 [inline] blk_add_partitions block/partitions/core.c:635 [inline] bdev_disk_changed+0x9e5/0xe20 block/partitions/core.c:695 loop_reread_partitions drivers/block/loop.c:443 [inline] loop_set_status+0x5af/0x670 drivers/block/loop.c:1272 loop_set_status64 drivers/block/loop.c:1368 [inline] lo_ioctl+0x66d/0x1390 drivers/block/loop.c:1554 blkdev_ioctl+0x387/0x460 block/ioctl.c:797 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:597 [inline] __se_sys_ioctl+0xce/0x140 fs/ioctl.c:583 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:583 x64_sys_call+0x1563/0x3020 arch/x86/include/generated/asm/syscalls_64.h:17 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 read to 0xffffffff893ca388 of 8 bytes by task 21341 on cpu 0: 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 blk_crypto_submit_bio include/linux/blk-crypto.h:203 [inline] __bh_submit+0x2db/0x310 fs/buffer.c:1225 __block_write_full_folio+0x59c/0x8d0 fs/buffer.c:1910 block_write_full_folio+0x2c1/0x2e0 fs/buffer.c:-1 mpage_write_folio fs/mpage.c:640 [inline] __mpage_writepages+0x722/0x1370 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_fdatawrite+0x100/0x140 mm/filemap.c:418 writeback_inode fs/fat/inode.c:1888 [inline] fat_flush_inodes+0xcc/0x150 fs/fat/inode.c:1906 fat_truncate_blocks+0x536/0x5b0 fs/fat/file.c:399 fat_write_failed fs/fat/inode.c:219 [inline] fat_write_end+0xba/0x160 fs/fat/inode.c:247 generic_perform_write+0x314/0x490 mm/filemap.c:4379 __generic_file_write_iter+0x9e/0x120 mm/filemap.c:4475 generic_file_write_iter+0x77/0x1f0 mm/filemap.c:4501 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x57d/0x990 fs/read_write.c:687 ksys_pwrite64 fs/read_write.c:794 [inline] __do_sys_pwrite64 fs/read_write.c:802 [inline] __se_sys_pwrite64 fs/read_write.c:799 [inline] __x64_sys_pwrite64+0xfd/0x150 fs/read_write.c:799 x64_sys_call+0xa2a/0x3020 arch/x86/include/generated/asm/syscalls_64.h:19 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: 0x3fffffffffffeb85 -> 0x3fffffffffff0020 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 21341 Comm: syz.2.5891 Not tainted syzkaller #0 PREEMPT(lazy) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026 ================================================================== Buffer I/O error on dev loop2, logical block 75, lost async page write syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=152, nr_sectors = 2 limit=128 Buffer I/O error on dev loop2, logical block 76, lost async page write syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=170, nr_sectors = 6 limit=128 syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=174, nr_sectors = 2 limit=128 Buffer I/O error on dev loop2, logical block 87, lost async page write syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=176, nr_sectors = 2 limit=128 Buffer I/O error on dev loop2, logical block 88, lost async page write syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=178, nr_sectors = 6 limit=128 syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=182, nr_sectors = 2 limit=128 Buffer I/O error on dev loop2, logical block 91, lost async page write syz.2.5891: attempt to access beyond end of device loop2: rw=2049, sector=184, nr_sectors = 2 limit=128 Buffer I/O error on dev loop2, logical block 92, lost async page write Buffer I/O error on dev loop2, logical block 103, lost async page write Buffer I/O error on dev loop2, logical block 104, lost async page write Buffer I/O error on dev loop2, logical block 107, lost async page write Buffer I/O error on dev loop2, logical block 108, lost async page write syz.2.5891 (21341) used greatest stack depth: 9576 bytes left