VFS: Found a Xenix FS (block size = 1024) on device loop4 bridge0: received packet on syz_tun with own address as source address (addr:aa:aa:aa:aa:aa:aa, vlan:0) ------------[ cut here ]------------ WARNING: CPU: 0 PID: 8999 at fs/inode.c:389 inc_nlink+0x128/0x154 fs/inode.c:389 Modules linked in: CPU: 0 PID: 8999 Comm: syz.4.843 Not tainted syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025 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 : ffff800021ef7b90 x29: ffff800021ef7b90 x28: dfff800000000000 x27: 0000000000000000 x26: 1fffe0001fb0b15e x25: ffff800011d44c48 x24: 00000000000001c0 x23: 1fffe0001fb0b162 x22: dfff800000000000 x21: 0000000000000000 x20: ffff0000fd858ac8 x19: ffff0000fd858b10 x18: 0000000000000000 x17: ffff8000181f9000 x16: ffff8000082d25ac x15: 0000000000000002 x14: 00000000ffff8000 x13: 0000000008b9190c x12: 0000000000080000 x11: 000000000000c5c8 x10: ffff8000285a9000 x9 : ffff8000089fcc64 x8 : 000000000000c5c9 x7 : 0000000000000000 x6 : 000000000000003f x5 : 0000000000000040 x4 : 0000000000000001 x3 : 00000000000001c0 x2 : ffff0000e3027490 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:4114 do_mkdirat+0x1b4/0x3e0 fs/namei.c:4139 __do_sys_mkdirat fs/namei.c:4154 [inline] __se_sys_mkdirat fs/namei.c:4152 [inline] __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4152 __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: 2208 hardirqs last enabled at (2207): [] kasan_quarantine_put+0xc4/0x204 mm/kasan/quarantine.c:242 hardirqs last disabled at (2208): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:405 softirqs last enabled at (2124): [] local_bh_enable+0x10/0x34 include/linux/bottom_half.h:32 softirqs last disabled at (2122): [] local_bh_disable+0x10/0x34 include/linux/bottom_half.h:19 ---[ end trace 0000000000000000 ]--- ================================================================== BUG: KASAN: use-after-free in sysv_new_block+0x5d0/0x768 fs/sysv/balloc.c:113 Read of size 4 at addr ffff0001081090c8 by task syz.4.843/8999 CPU: 0 PID: 8999 Comm: syz.4.843 Tainted: G W syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025 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_load4_noabort+0x2c/0x38 mm/kasan/report_generic.c:350 sysv_new_block+0x5d0/0x768 fs/sysv/balloc.c:113 alloc_branch fs/sysv/itree.c:134 [inline] get_block+0x204/0x1210 fs/sysv/itree.c:253 __block_write_begin_int+0x34c/0x13b8 fs/buffer.c:1991 __block_write_begin+0x7c/0xa0 fs/buffer.c:2041 sysv_prepare_chunk+0x3c/0x50 fs/sysv/itree.c:468 sysv_make_empty+0x94/0x4f8 fs/sysv/dir.c:257 sysv_mkdir+0x88/0x138 fs/sysv/namei.c:130 vfs_mkdir+0x314/0x4d4 fs/namei.c:4114 do_mkdirat+0x1b4/0x3e0 fs/namei.c:4139 __do_sys_mkdirat fs/namei.c:4154 [inline] __se_sys_mkdirat fs/namei.c:4152 [inline] __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4152 __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:000000003b5b8e58 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x148109 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: ffff000108108f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff000108109000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >ffff000108109080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff000108109100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff000108109180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ==================================================================