==================================================================
BUG: KASAN: use-after-free in ext4_ext_rm_leaf fs/ext4/extents.c:2602 [inline]
BUG: KASAN: use-after-free in ext4_ext_remove_space+0x348b/0x40d0 fs/ext4/extents.c:2940
Read of size 4 at addr ffff88813f560c18 by task syz-executor/285

CPU: 1 PID: 285 Comm: syz-executor Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0x110/0x170 lib/dump_stack.c:106
 print_address_description+0x71/0x200 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:420
 kasan_report+0x122/0x150 mm/kasan/report.c:524
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:350
 ext4_ext_rm_leaf fs/ext4/extents.c:2602 [inline]
 ext4_ext_remove_space+0x348b/0x40d0 fs/ext4/extents.c:2940
 ext4_ext_truncate+0x200/0x320 fs/ext4/extents.c:4470
 ext4_truncate+0x9be/0xfb0 fs/ext4/inode.c:4297
 ext4_evict_inode+0xccf/0x1470 fs/ext4/inode.c:286
 evict+0x4d7/0x8f0 fs/inode.c:708
 iput_final fs/inode.c:1844 [inline]
 iput+0x620/0x670 fs/inode.c:1870
 do_unlinkat+0x380/0x6d0 fs/namei.c:4404
 __do_sys_unlink fs/namei.c:4445 [inline]
 __se_sys_unlink fs/namei.c:4443 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4443
 x64_sys_call+0x958/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:88
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fc9d039b717
Code: 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 57 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 01 c3 48 c7 c2 e8 ff ff ff f7 d8 64 89 02 b8
RSP: 002b:00007ffed3359df8 EFLAGS: 00000206 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fc9d039b717
RDX: 00007ffed3359e20 RSI: 00007ffed3359eb0 RDI: 00007ffed3359eb0
RBP: 00007ffed3359eb0 R08: 00007ffed335aeb0 R09: 00000000ffffffff
R10: 0000000000000100 R11: 0000000000000206 R12: 00007ffed335afa0
R13: 00007fc9d0431ef0 R14: 000000000000a559 R15: 00007ffed335c070
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004fd5800 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x13f560
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 708, tgid 707 (syz.3.108), ts 40633570212, free_ts 41181648878
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2670
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2677
 get_page_from_freelist+0x2d12/0x2d80 mm/page_alloc.c:4583
 __alloc_pages+0x1d9/0x480 mm/page_alloc.c:5897
 __folio_alloc+0x12/0x40 mm/page_alloc.c:5929
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 shmem_alloc_folio mm/shmem.c:1601 [inline]
 shmem_alloc_and_acct_folio+0x6dd/0x8c0 mm/shmem.c:1626
 shmem_get_folio_gfp+0x119f/0x2230 mm/shmem.c:1955
 shmem_get_folio mm/shmem.c:2086 [inline]
 shmem_write_begin+0xea/0x2c0 mm/shmem.c:2571
 generic_perform_write+0x32d/0x740 mm/filemap.c:3903
 __generic_file_write_iter+0x17a/0x230 mm/filemap.c:4002
 generic_file_write_iter+0xae/0x310 mm/filemap.c:4031
 call_write_iter include/linux/fs.h:2282 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x603/0xce0 fs/read_write.c:584
 ksys_write+0x149/0x250 fs/read_write.c:637
 __do_sys_write fs/read_write.c:649 [inline]
 __se_sys_write fs/read_write.c:646 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:646
 x64_sys_call+0x27b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1578 [inline]
 free_pcp_prepare mm/page_alloc.c:1652 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3618
 free_unref_page_list+0x117/0x8c0 mm/page_alloc.c:3769
 release_pages+0xaf2/0xb50 mm/swap.c:1048
 __pagevec_release+0x71/0xe0 mm/swap.c:1068
 pagevec_release include/linux/pagevec.h:71 [inline]
 folio_batch_release include/linux/pagevec.h:135 [inline]
 shmem_undo_range+0x574/0x1540 mm/shmem.c:955
 shmem_truncate_range mm/shmem.c:1071 [inline]
 shmem_evict_inode+0x255/0xa50 mm/shmem.c:1180
 evict+0x4d7/0x8f0 fs/inode.c:708
 iput_final fs/inode.c:1844 [inline]
 iput+0x620/0x670 fs/inode.c:1870
 dentry_unlink_inode+0x33d/0x3f0 fs/dcache.c:405
 __dentry_kill+0x460/0x670 fs/dcache.c:611
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x42/0x80 fs/dcache.c:918
 __fput+0x5be/0x8f0 fs/file_table.c:328
 ____fput+0x15/0x20 fs/file_table.c:348
 task_work_run+0x1e1/0x250 kernel/task_work.c:203
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0x9b/0xb0 kernel/entry/common.c:177

Memory state around the buggy address:
 ffff88813f560b00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88813f560b80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88813f560c00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88813f560c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88813f560d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop1): ext4_lookup:1858: inode #16: comm syz-executor: iget: bad extended attribute block 8
EXT4-fs error (device loop1): ext4_lookup:1858: inode #16: comm syz-executor: iget: bad extended attribute block 8
EXT4-fs (loop1): unmounting filesystem.