==================================================================
BUG: KASAN: slab-use-after-free in vma_multi_allowed+0x172/0x1b0
Read of size 8 at addr ffff8880171d1cd8 by task syz-executor.1/5604

CPU: 1 UID: 0 PID: 5604 Comm: syz-executor.1 Not tainted 6.17.0-rc1-next-20250815 #1 PREEMPT(voluntary) 
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xca/0x120
 print_report+0xcb/0x610
 kasan_report+0xca/0x100
 vma_multi_allowed+0x172/0x1b0
 __do_sys_mremap+0xcb7/0x1410
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f145a52cb19
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1457aa2188 EFLAGS: 00000246 ORIG_RAX: 0000000000000019
RAX: ffffffffffffffda RBX: 00007f145a63ff60 RCX: 00007f145a52cb19
RDX: 0000000000001000 RSI: 0000000000001000 RDI: 0000000020871000
RBP: 00007f145a586f6d R08: 0000000020ffd000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd65a58c4f R14: 00007f1457aa2300 R15: 0000000000022000
 </TASK>

Allocated by task 277:
 kasan_save_stack+0x24/0x50
 kasan_save_track+0x14/0x30
 __kasan_slab_alloc+0x59/0x70
 kmem_cache_alloc_noprof+0x13c/0x3d0
 vm_area_dup+0x25/0x6f0
 dup_mmap+0x80d/0x1d10
 copy_process+0x6faf/0x73e0
 kernel_clone+0xea/0x7f0
 __do_sys_clone+0xce/0x120
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Freed by task 5574:
 kasan_save_stack+0x24/0x50
 kasan_save_track+0x14/0x30
 kasan_save_free_info+0x3a/0x60
 __kasan_slab_free+0x3f/0x50
 slab_free_after_rcu_debug+0xd6/0x290
 rcu_core+0x7c8/0x1800
 handle_softirqs+0x1b1/0x770
 do_softirq+0x48/0x80
 __local_bh_enable_ip+0xf1/0x110
 kernel_fpu_end+0x5e/0x70
 crc32c+0x2e5/0x350
 ext4_superblock_csum_set+0xc0/0x130
 ext4_orphan_add+0xaf3/0x1320
 ext4_file_write_iter+0xda6/0x1990
 iter_file_splice_write+0x929/0x1140
 direct_splice_actor+0x192/0x7b0
 splice_direct_to_actor+0x347/0x9d0
 do_splice_direct+0x179/0x250
 do_sendfile+0xa8e/0xdc0
 __x64_sys_sendfile64+0x1d3/0x210
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Last potentially related work creation:
 kasan_save_stack+0x24/0x50
 kasan_record_aux_stack+0x89/0xa0
 kmem_cache_free+0x145/0x460
 vms_complete_munmap_vmas+0x549/0x9f0
 do_vmi_align_munmap+0x3db/0x550
 do_vmi_munmap+0x1eb/0x3c0
 do_munmap+0xbd/0x100
 mremap_to+0x242/0x450
 __do_sys_mremap+0xca2/0x1410
 do_syscall_64+0xbf/0x360
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff8880171d1c80
 which belongs to the cache vm_area_struct of size 256
The buggy address is located 88 bytes inside of
 freed 256-byte region [ffff8880171d1c80, ffff8880171d1d80)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x171d1
memcg:ffff888013f0f081
flags: 0x100000000000000(node=0|zone=1)
page_type: f5(slab)
raw: 0100000000000000 ffff888008fffc80 dead000000000122 0000000000000000
raw: 0000000000000000 00000000000c000c 00000000f5000000 ffff888013f0f081
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880171d1b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880171d1c00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
>ffff8880171d1c80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                    ^
 ffff8880171d1d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880171d1d80: fc fc fc fc fc fc fc fc 00 00 00 00 00 00 00 00
==================================================================
journal_path: not usable as path
EXT4-fs: error: could not find journal device path
journal_path: not usable as path
EXT4-fs: error: could not find journal device path