syzbot

loop9: detected capacity change from 0 to 7
Buffer I/O error on dev loop9, logical block 0, async page read
==================================================================
BUG: KCSAN: data-race in data_alloc / prb_reserve

write to 0xffffffff86869560 of 8 bytes by task 26279 on cpu 1:
 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
 __ext4_msg+0x18f/0x1a0 fs/ext4/super.c:981
 ext4_fill_super+0x2d05/0x34e0 fs/ext4/super.c:5739
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1681
 get_tree_bdev+0x1f/0x30 fs/super.c:1704
 ext4_get_tree+0x1c/0x30 fs/ext4/super.c:5756
 vfs_get_tree+0x54/0x1d0 fs/super.c:1804
 do_new_mount+0x207/0x680 fs/namespace.c:3902
 path_mount+0x4a4/0xb20 fs/namespace.c:4226
 do_mount fs/namespace.c:4239 [inline]
 __do_sys_mount fs/namespace.c:4450 [inline]
 __se_sys_mount+0x28f/0x2e0 fs/namespace.c:4427
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4427
 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+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86869560 of 8 bytes by task 26281 on cpu 0:
 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
 buffer_io_error fs/buffer.c:130 [inline]
 end_buffer_async_read fs/buffer.c:271 [inline]
 end_buffer_async_read_io+0x232/0x250 fs/buffer.c:380
 end_bio_bh_io_sync+0x76/0xa0 fs/buffer.c:2783
 bio_endio+0x374/0x410 block/bio.c:1645
 blk_mq_submit_bio+0x3c3/0xf50 block/blk-mq.c:-1
 __submit_bio+0xed/0x4d0 block/blk-core.c:635
 __submit_bio_noacct_mq block/blk-core.c:722 [inline]
 submit_bio_noacct_nocheck+0x208/0x6a0 block/blk-core.c:751
 submit_bio_noacct+0x6c8/0x8f0 block/blk-core.c:874
 submit_bio+0x227/0x240 block/blk-core.c:916
 submit_bh_wbc+0x2e0/0x320 fs/buffer.c:2831
 submit_bh fs/buffer.c:2836 [inline]
 block_read_full_folio+0x658/0x6a0 fs/buffer.c:2468
 blkdev_read_folio+0x1c/0x30 block/fops.c:491
 filemap_read_folio mm/filemap.c:2412 [inline]
 do_read_cache_folio+0x196/0x5b0 mm/filemap.c:3894
 read_cache_folio+0x3c/0x50 mm/filemap.c:3926
 read_mapping_folio include/linux/pagemap.h:972 [inline]
 read_part_sector+0x6f/0x150 block/partitions/core.c:722
 msdos_partition+0x82/0x20d0 block/partitions/msdos.c:592
 check_partition block/partitions/core.c:141 [inline]
 blk_add_partitions block/partitions/core.c:589 [inline]
 bdev_disk_changed+0x4b9/0xcb0 block/partitions/core.c:693
 loop_reread_partitions+0x48/0xb0 drivers/block/loop.c:440
 loop_configure+0xa18/0xa50 drivers/block/loop.c:1085
 lo_ioctl+0x559/0x15d0 drivers/block/loop.c:-1
 blkdev_ioctl+0x34f/0x440 block/ioctl.c:704
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl+0xce/0x140 fs/ioctl.c:893
 __x64_sys_ioctl+0x43/0x50 fs/ioctl.c:893
 x64_sys_call+0x19a8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000077a20 -> 0x00000000001238c8

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 26281 Comm: syz.4.6904 Not tainted 6.16.0-rc4-syzkaller-00049-gb4911fb0b060 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================
Buffer I/O error on dev loop9, logical block 0, async page read
 loop9: unable to read partition table
loop_reread_partitions: partition scan of loop9 (þ被xüŸÑø éÚ¬§½dG¤´à–ƒÝ¡¯ �â·û

) failed (rc=-5)