loop5: detected capacity change from 0 to 128
FAT-fs (loop5): Directory bread(block 162) failed
FAT-fs (loop5): Directory bread(block 163) failed
FAT-fs (loop5): Directory bread(block 164) failed
==================================================================
BUG: KCSAN: data-race in _prb_read_valid / data_alloc

write to 0xffffffff86868b50 of 8 bytes by task 25820 on cpu 1:
 data_alloc+0x2f7/0x380 kernel/printk/printk_ringbuffer.c:1101
 prb_reserve+0x964/0xb60 kernel/printk/printk_ringbuffer.c:1685
 vprintk_store+0x56d/0x860 kernel/printk/printk.c:2299
 vprintk_emit+0x10d/0x580 kernel/printk/printk.c:2399
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2448
 ib_get_eth_speed+0x33d/0x4b0 drivers/infiniband/core/verbs.c:2006
 siw_query_port+0x3a/0x2d0 drivers/infiniband/sw/siw/siw_verbs.c:179
 iw_query_port drivers/infiniband/core/device.c:2137 [inline]
 ib_query_port+0x393/0x3d0 drivers/infiniband/core/device.c:2178
 ib_setup_port_attrs+0x14a/0x1430 drivers/infiniband/core/sysfs.c:1429
 add_one_compat_dev+0x261/0x360 drivers/infiniband/core/device.c:1005
 rdma_dev_init_net+0x182/0x210 drivers/infiniband/core/device.c:1221
 ops_init+0x22a/0x2e0 net/core/net_namespace.c:137
 setup_net+0x95/0x220 net/core/net_namespace.c:445
 copy_net_ns+0x309/0x460 net/core/net_namespace.c:580
 create_new_namespaces+0x20e/0x400 kernel/nsproxy.c:130
 unshare_nsproxy_namespaces+0xe8/0x120 kernel/nsproxy.c:226
 ksys_unshare+0x3d0/0x6d0 kernel/fork.c:3129
 __do_sys_unshare kernel/fork.c:3200 [inline]
 __se_sys_unshare kernel/fork.c:3198 [inline]
 __x64_sys_unshare+0x1f/0x30 kernel/fork.c:3198
 x64_sys_call+0x2ae6/0x3000 arch/x86/include/generated/asm/syscalls_64.h:273
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86868b50 of 16 bytes by task 25837 on cpu 0:
 desc_read kernel/printk/printk_ringbuffer.c:479 [inline]
 desc_read_finalized_seq kernel/printk/printk_ringbuffer.c:1892 [inline]
 prb_read kernel/printk/printk_ringbuffer.c:1940 [inline]
 _prb_read_valid+0x1bc/0x920 kernel/printk/printk_ringbuffer.c:2131
 prb_read_valid+0x3c/0x60 kernel/printk/printk_ringbuffer.c:2203
 __console_flush_and_unlock kernel/printk/printk.c:3277 [inline]
 console_unlock+0x164/0x2e0 kernel/printk/printk.c:3298
 vprintk_emit+0x3b5/0x580 kernel/printk/printk.c:2423
 vprintk_default+0x26/0x30 kernel/printk/printk.c:2438
 vprintk+0x1d/0x30 kernel/printk/printk_safe.c:82
 _printk+0x79/0xa0 kernel/printk/printk.c:2448
 _fat_msg+0xa4/0xd0 fs/fat/misc.c:62
 fat__get_entry fs/fat/dir.c:102 [inline]
 fat_get_entry+0x52b/0x5d0 fs/fat/dir.c:128
 fat_get_short_entry fs/fat/dir.c:885 [inline]
 fat_subdirs+0x59/0x190 fs/fat/dir.c:951
 fat_read_root+0x316/0x360 fs/fat/inode.c:1348
 fat_fill_super+0x15bb/0x1ce0 fs/fat/inode.c:1821
 vfat_fill_super+0x24/0x30 fs/fat/namei_vfat.c:1197
 get_tree_bdev_flags+0x291/0x300 fs/super.c:1699
 get_tree_bdev+0x1f/0x30 fs/super.c:1722
 vfat_get_tree+0x1c/0x30 fs/fat/namei_vfat.c:1202
 vfs_get_tree+0x57/0x1d0 fs/super.c:1759
 fc_mount fs/namespace.c:1199 [inline]
 do_new_mount_fc fs/namespace.c:3636 [inline]
 do_new_mount+0x24d/0x6a0 fs/namespace.c:3712
 path_mount+0x4ab/0xb80 fs/namespace.c:4022
 do_mount fs/namespace.c:4035 [inline]
 __do_sys_mount fs/namespace.c:4224 [inline]
 __se_sys_mount+0x28c/0x2e0 fs/namespace.c:4201
 __x64_sys_mount+0x67/0x80 fs/namespace.c:4201
 x64_sys_call+0x2cca/0x3000 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 25837 Comm: syz.5.3210 Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================
FAT-fs (loop5): Directory bread(block 165) failed
FAT-fs (loop5): Directory bread(block 166) failed
FAT-fs (loop5): Directory bread(block 167) failed
FAT-fs (loop5): Directory bread(block 168) failed
FAT-fs (loop5): Directory bread(block 169) failed
netlink: 24 bytes leftover after parsing attributes in process `syz.5.3210'.
netlink: 24 bytes leftover after parsing attributes in process `syz.5.3210'.
FAT-fs (loop5): Directory bread(block 162) failed
FAT-fs (loop5): Directory bread(block 163) failed
syz.5.3210: attempt to access beyond end of device
loop5: rw=3, sector=226, nr_sectors = 6 limit=128
syz.5.3210: attempt to access beyond end of device
loop5: rw=2051, sector=232, nr_sectors = 2 limit=128