loop4: detected capacity change from 0 to 128
VFS: Found a Xenix FS (block size = 1024) on device loop4
------------[ cut here ]------------
WARNING: CPU: 1 PID: 4476 at fs/inode.c:389 inc_nlink+0x128/0x154 fs/inode.c:389
Modules linked in:
CPU: 1 PID: 4476 Comm: syz.4.15 Not tainted 6.1.148-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : inc_nlink+0x128/0x154 fs/inode.c:389
lr : inc_nlink+0x128/0x154 fs/inode.c:389
sp : ffff8000215f7b90
x29: ffff8000215f7b90 x28: dfff800000000000 x27: 0000000000000000
x26: 1fffe0001ebbd80c x25: ffff800011d35208 x24: 00000000000001c0
x23: 1fffe0001ebbd810 x22: dfff800000000000 x21: 0000000000000000
x20: ffff0000f5dec038 x19: ffff0000f5dec080 x18: 0000000000000000
x17: ffff8000181e7000 x16: ffff8000082d2370 x15: 0000000000000002
x14: 00000000ffff8000 x13: 000000003bcdb8d7 x12: 0000000000080000
x11: 0000000000006209 x10: ffff80002c68a000 x9 : ffff8000089fbf80
x8 : 000000000000620a x7 : 0000000000000000 x6 : 000000000000003f
x5 : 0000000000000040 x4 : 0000000000000001 x3 : 00000000000001c0
x2 : ffff0000dfbbb1a0 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
 inc_nlink+0x128/0x154 fs/inode.c:389
 inode_inc_link_count include/linux/fs.h:2576 [inline]
 sysv_mkdir+0x2c/0x138 fs/sysv/namei.c:119
 vfs_mkdir+0x314/0x4d4 fs/namei.c:4106
 do_mkdirat+0x1b4/0x3e0 fs/namei.c:4131
 __do_sys_mkdirat fs/namei.c:4146 [inline]
 __se_sys_mkdirat fs/namei.c:4144 [inline]
 __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4144
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
irq event stamp: 8454
hardirqs last  enabled at (8453): [<ffff8000088d7428>] kasan_quarantine_put+0xc4/0x204 mm/kasan/quarantine.c:242
hardirqs last disabled at (8454): [<ffff800011948d00>] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405
softirqs last  enabled at (8394): [<ffff800008030900>] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32
softirqs last disabled at (8392): [<ffff8000080308cc>] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19
---[ end trace 0000000000000000 ]---
==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0xd8c/0xf04 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff0000e44a71ce by task syz.4.15/4476

CPU: 1 PID: 4476 Comm: syz.4.15 Tainted: G        W          6.1.148-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/30/2025
Call trace:
 dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0x100 mm/kasan/report.c:524
 __asan_report_load2_noabort+0x2c/0x38 mm/kasan/report_generic.c:349
 sysv_new_inode+0xd8c/0xf04 fs/sysv/ialloc.c:153
 sysv_mkdir+0x44/0x138 fs/sysv/namei.c:121
 vfs_mkdir+0x314/0x4d4 fs/namei.c:4106
 do_mkdirat+0x1b4/0x3e0 fs/namei.c:4131
 __do_sys_mkdirat fs/namei.c:4146 [inline]
 __se_sys_mkdirat fs/namei.c:4144 [inline]
 __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4144
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x138 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the physical page:
page:000000004099a1fb refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1244a7
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000e44a7080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e44a7100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000e44a7180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff0000e44a7200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e44a7280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================