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BUG: KASAN: use-after-free in ext4_insert_dentry+0x36a/0x6d0 fs/ext4/namei.c:2119
Write of size 251 at addr ffff88804589af14 by task syz.0.0/5333

CPU: 0 UID: 0 PID: 5333 Comm: syz.0.0 Not tainted 6.12.0-syzkaller-09073-g9f16d5e6f220 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 __asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
 ext4_insert_dentry+0x36a/0x6d0 fs/ext4/namei.c:2119
 add_dirent_to_buf+0x3d9/0x750 fs/ext4/namei.c:2164
 make_indexed_dir+0xf98/0x1600 fs/ext4/namei.c:2361
 ext4_add_entry+0xcf7/0xfa0 fs/ext4/namei.c:2462
 ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2803
 ext4_symlink+0x920/0xb50 fs/ext4/namei.c:3438
 vfs_symlink+0x137/0x2e0 fs/namei.c:4669
 do_symlinkat+0x222/0x3a0 fs/namei.c:4695
 __do_sys_symlink fs/namei.c:4716 [inline]
 __se_sys_symlink fs/namei.c:4714 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4714
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1dddd7e819
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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f1ddeb2c038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f1dddf36080 RCX: 00007f1dddd7e819
RDX: 0000000000000000 RSI: 0000000020000cc0 RDI: 0000000020000dc0
RBP: 00007f1ddddf175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f1dddf36080 R15: 00007ffee70a6c28
 </TASK>

The buggy address belongs to the physical page:
page: refcount:3 mapcount:0 mapping:ffff88801aa1cd78 index:0x3f pfn:0x4589a
memcg:ffff888030aee000
aops:def_blk_aops ino:700000 dentry name(?):""
flags: 0x4fff08000004214(referenced|dirty|workingset|private|node=1|zone=1|lastcpupid=0x7ff)
raw: 04fff08000004214 0000000000000000 dead000000000122 ffff88801aa1cd78
raw: 000000000000003f ffff888043ed50e8 00000003ffffffff ffff888030aee000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x148c40(GFP_NOFS|__GFP_NOFAIL|__GFP_COMP|__GFP_HARDWALL), pid 5333, tgid 5331 (syz.0.0), ts 59913739582, free_ts 59823530961
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0x3649/0x3790 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 alloc_pages_noprof mm/mempolicy.c:2344 [inline]
 folio_alloc_noprof+0x128/0x180 mm/mempolicy.c:2351
 filemap_alloc_folio_noprof+0xdf/0x500 mm/filemap.c:1009
 __filemap_get_folio+0x446/0xbd0 mm/filemap.c:1951
 grow_dev_folio fs/buffer.c:1039 [inline]
 grow_buffers fs/buffer.c:1105 [inline]
 __getblk_slow fs/buffer.c:1131 [inline]
 bdev_getblk+0x1d8/0x550 fs/buffer.c:1431
 getblk_unmovable include/linux/buffer_head.h:369 [inline]
 ext4_getblk+0x31b/0x880 fs/ext4/inode.c:864
 ext4_bread+0x2e/0x180 fs/ext4/inode.c:912
 ext4_append+0x327/0x5c0 fs/ext4/namei.c:83
 make_indexed_dir+0x523/0x1600 fs/ext4/namei.c:2282
 ext4_add_entry+0xcf7/0xfa0 fs/ext4/namei.c:2462
 ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2803
 ext4_symlink+0x920/0xb50 fs/ext4/namei.c:3438
 vfs_symlink+0x137/0x2e0 fs/namei.c:4669
page last free pid 1082 tgid 1082 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_page+0xdf9/0x1140 mm/page_alloc.c:2657
 discard_slab mm/slub.c:2677 [inline]
 __put_partials+0xeb/0x130 mm/slub.c:3145
 put_cpu_partial+0x17c/0x250 mm/slub.c:3220
 __slab_free+0x2ea/0x3d0 mm/slub.c:4449
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x9a/0x140 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x14f/0x170 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x23/0x80 mm/kasan/common.c:329
 kasan_slab_alloc include/linux/kasan.h:250 [inline]
 slab_post_alloc_hook mm/slub.c:4085 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 kmem_cache_alloc_node_noprof+0x16b/0x320 mm/slub.c:4186
 __alloc_skb+0x1c3/0x440 net/core/skbuff.c:668
 alloc_skb include/linux/skbuff.h:1323 [inline]
 alloc_skb_with_frags+0xc3/0x820 net/core/skbuff.c:6612
 sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2881
 sock_alloc_send_skb include/net/sock.h:1797 [inline]
 mld_newpack+0x1c3/0xaf0 net/ipv6/mcast.c:1747
 add_grhead net/ipv6/mcast.c:1850 [inline]
 add_grec+0x1492/0x19a0 net/ipv6/mcast.c:1988
 mld_send_initial_cr+0x228/0x4b0 net/ipv6/mcast.c:2234
 ipv6_mc_dad_complete+0x88/0x490 net/ipv6/mcast.c:2245
 addrconf_dad_completed+0x712/0xcd0 net/ipv6/addrconf.c:4342

Memory state around the buggy address:
 ffff88804589af00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88804589af80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88804589b000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff88804589b080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88804589b100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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