==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
Read of size 4 at addr ffff88811a199018 by task syz.6.391/1701

CPU: 1 PID: 1701 Comm: syz.6.391 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
 ext4_ext_map_blocks+0x20b/0x5dd0 fs/ext4/extents.c:4166
 ext4_map_blocks+0x3b1/0x1bd0 fs/ext4/inode.c:601
 ext4_alloc_file_blocks+0x396/0xb40 fs/ext4/extents.c:4529
 ext4_fallocate+0x798/0x1a70 fs/ext4/extents.c:4814
 vfs_fallocate+0x4b4/0x590 fs/open.c:310
 ioctl_preallocate fs/ioctl.c:494 [inline]
 file_ioctl fs/ioctl.c:534 [inline]
 do_vfs_ioctl+0x1154/0x14c0 fs/ioctl.c:732
 __do_sys_ioctl fs/ioctl.c:751 [inline]
 __se_sys_ioctl+0x9f/0x1a0 fs/ioctl.c:739
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:739
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7ff675883819
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 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 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ff67429c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ff675afd180 RCX: 00007ff675883819
RDX: 00002000000003c0 RSI: 0000000040305828 RDI: 0000000000000008
RBP: 00007ff675919c91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ff675afd218 R14: 00007ff675afd180 R15: 00007ffc603a4258

Allocated by task 1434:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 shmem_alloc_inode+0x1a/0x30 mm/shmem.c:3816
 alloc_inode fs/inode.c:233 [inline]
 new_inode_pseudo+0x62/0x210 fs/inode.c:968
 new_inode+0x28/0x1e0 fs/inode.c:997
 shmem_get_inode+0x34a/0x9d0 mm/shmem.c:2311
 shmem_mknod+0x5c/0x1c0 mm/shmem.c:2894
 shmem_mkdir+0x2e/0x60 mm/shmem.c:2945
 vfs_mkdir+0x4c7/0x6a0 fs/namei.c:3798
 ovl_do_mkdir fs/overlayfs/overlayfs.h:159 [inline]
 ovl_mkdir_real+0x4f/0x190 fs/overlayfs/dir.c:145
 ovl_workdir_create+0x2e3/0x5a0 fs/overlayfs/super.c:773
 ovl_make_workdir fs/overlayfs/super.c:1321 [inline]
 ovl_get_workdir+0x350/0xda0 fs/overlayfs/super.c:1458
 ovl_fill_super+0x15ff/0x2560 fs/overlayfs/super.c:1998
 mount_nodev+0x5c/0xf0 fs/super.c:1488
 ovl_mount+0x2c/0x40 fs/overlayfs/super.c:2082
 legacy_get_tree+0xed/0x190 fs/fs_context.c:593
 vfs_get_tree+0x89/0x260 fs/super.c:1572
 do_new_mount+0x25a/0xa20 fs/namespace.c:3006
 path_mount+0x585/0xc90 fs/namespace.c:3336
 do_mount fs/namespace.c:3349 [inline]
 __do_sys_mount fs/namespace.c:3557 [inline]
 __se_sys_mount+0x320/0x390 fs/namespace.c:3534
 __x64_sys_mount+0xbf/0xd0 fs/namespace.c:3534
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 1407:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 shmem_free_in_core_inode+0x90/0xb0 mm/shmem.c:3826
 i_callback+0x4c/0x70 fs/inode.c:222
 rcu_do_batch+0x4ef/0xab0 kernel/rcu/tree.c:2494
 rcu_core+0x577/0xd80 kernel/rcu/tree.c:2735
 rcu_core_si+0x9/0x10 kernel/rcu/tree.c:2748
 __do_softirq+0x255/0x563 kernel/softirq.c:309

Last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x10b0 kernel/rcu/tree.c:3054
 destroy_inode fs/inode.c:288 [inline]
 evict+0x881/0x930 fs/inode.c:629
 iput_final fs/inode.c:1736 [inline]
 iput+0x638/0x7c0 fs/inode.c:1762
 d_delete_notify include/linux/fsnotify.h:267 [inline]
 vfs_rmdir+0x2bd/0x3e0 fs/namei.c:3873
 do_rmdir+0x230/0x630 fs/namei.c:3920
 __do_sys_unlinkat fs/namei.c:4084 [inline]
 __se_sys_unlinkat fs/namei.c:4078 [inline]
 __x64_sys_unlinkat+0xc7/0xf0 fs/namei.c:4078
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Second to last potentially related work creation:
 kasan_save_stack+0x3a/0x60 mm/kasan/common.c:38
 __kasan_record_aux_stack+0xd2/0x100 mm/kasan/generic.c:348
 kasan_record_aux_stack_noalloc+0xb/0x10 mm/kasan/generic.c:358
 __call_rcu kernel/rcu/tree.c:2980 [inline]
 call_rcu+0x11a/0x10b0 kernel/rcu/tree.c:3054
 destroy_inode fs/inode.c:288 [inline]
 evict+0x881/0x930 fs/inode.c:629
 iput_final fs/inode.c:1736 [inline]
 iput+0x638/0x7c0 fs/inode.c:1762
 d_delete_notify include/linux/fsnotify.h:267 [inline]
 vfs_rmdir+0x2bd/0x3e0 fs/namei.c:3873
 do_rmdir+0x230/0x630 fs/namei.c:3920
 __do_sys_unlinkat fs/namei.c:4084 [inline]
 __se_sys_unlinkat fs/namei.c:4078 [inline]
 __x64_sys_unlinkat+0xc7/0xf0 fs/namei.c:4078
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff88811a198e80
 which belongs to the cache shmem_inode_cache of size 800
The buggy address is located 408 bytes inside of
 800-byte region [ffff88811a198e80, ffff88811a1991a0)
The buggy address belongs to the page:
page:ffffea0004686600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11a198
head:ffffea0004686600 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea0004677000 0000000d0000000d ffff88810018a600
raw: 0000000000000000 0000000000110011 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 439, ts 26714085177, free_ts 26709162944
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x290/0x620 mm/page_alloc.c:5384
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x1ac/0x2d0 mm/slub.c:2965
 shmem_alloc_inode+0x1a/0x30 mm/shmem.c:3816
 alloc_inode fs/inode.c:233 [inline]
 new_inode_pseudo+0x62/0x210 fs/inode.c:968
 new_inode+0x28/0x1e0 fs/inode.c:997
 shmem_get_inode+0x34a/0x9d0 mm/shmem.c:2311
 shmem_mknod+0x5c/0x1c0 mm/shmem.c:2894
 shmem_create+0x2b/0x40 mm/shmem.c:2954
 lookup_open fs/namei.c:3255 [inline]
 open_last_lookups fs/namei.c:3325 [inline]
 path_openat+0x170a/0x31c0 fs/namei.c:3514
 do_filp_open+0x1e2/0x410 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 __free_pages_ok+0x80b/0x830 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5445 [inline]
 __free_pages+0xd8/0x3b0 mm/page_alloc.c:5454
 __free_slab+0xcf/0x190 mm/slub.c:1899
 free_slab mm/slub.c:1914 [inline]
 discard_slab+0x29/0x40 mm/slub.c:1920
 __slab_free+0x313/0x3a0 mm/slub.c:3136
 do_slab_free mm/slub.c:3196 [inline]
 ___cache_free+0x10e/0x130 mm/slub.c:3215
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 getname_flags+0xb9/0x500 fs/namei.c:141
 user_path_at_empty+0x2f/0x50 fs/namei.c:2748
 user_path_at include/linux/namei.h:60 [inline]
 vfs_statx+0x10a/0x530 fs/stat.c:193
 vfs_fstatat fs/stat.c:215 [inline]
 __do_sys_newfstatat fs/stat.c:383 [inline]
 __se_sys_newfstatat+0x10e/0x3d0 fs/stat.c:377

Memory state around the buggy address:
 ffff88811a198f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811a198f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811a199000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff88811a199080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811a199100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
EXT4-fs error (device loop6): ext4_ext_precache:625: inode #15: comm syz.6.391: pblk 129 bad header/extent: invalid magic - magic 0, entries 59906, max 1(0), depth 0(0)