==================================================================
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 ffff888156fb3018 by task kworker/u4:0/7

CPU: 1 PID: 7 Comm: kworker/u4:0 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: writeback wb_workfn (flush-7:9)
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 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+0x1dc/0x5d80 fs/ext4/extents.c:4160
 ext4_map_blocks+0x978/0x1bc0 fs/ext4/inode.c:674
 mpage_map_one_extent fs/ext4/inode.c:2452 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2505 [inline]
 ext4_writepages+0x11d5/0x2e00 fs/ext4/inode.c:2873
 do_writepages+0x12a/0x270 mm/page-writeback.c:2380
 __writeback_single_inode+0xd5/0xa20 fs/fs-writeback.c:1470
 writeback_sb_inodes+0x860/0x1400 fs/fs-writeback.c:1733
 wb_writeback+0x3e3/0xb90 fs/fs-writeback.c:1908
 wb_do_writeback fs/fs-writeback.c:2053 [inline]
 wb_workfn+0x38f/0xe20 fs/fs-writeback.c:2094
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

The buggy address belongs to the page:
page:ffffea00055becc0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x156fb3
flags: 0x4000000000000000()
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 0x101cca(GFP_HIGHUSER_MOVABLE|__GFP_WRITE), pid 14739, ts 591954683691, free_ts 591958239890
 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+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370
 __alloc_pages include/linux/gfp.h:544 [inline]
 __alloc_pages_node include/linux/gfp.h:557 [inline]
 alloc_pages_node include/linux/gfp.h:571 [inline]
 alloc_pages include/linux/gfp.h:590 [inline]
 __page_cache_alloc include/linux/pagemap.h:290 [inline]
 pagecache_get_page+0x642/0x930 mm/filemap.c:1848
 grab_cache_page_write_begin+0x59/0xb0 mm/filemap.c:3459
 ext4_write_begin+0x27b/0x15a0 fs/ext4/inode.c:1208
 ext4_da_write_begin+0x455/0xe80 fs/ext4/inode.c:3033
 generic_perform_write+0x2be/0x510 mm/filemap.c:3509
 ext4_buffered_write_iter+0x4b8/0x640 fs/ext4/file.c:271
 ext4_file_write_iter+0x536/0x1980 fs/ext4/file.c:-1
 do_iter_readv_writev+0x491/0x600 fs/read_write.c:-1
 do_iter_write+0x189/0x630 fs/read_write.c:866
 vfs_iter_write+0x7d/0xa0 fs/read_write.c:907
 iter_file_splice_write+0x650/0xc30 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0xe9/0x120 fs/splice.c:936
 splice_direct_to_actor+0x4c0/0xb10 fs/splice.c:891
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_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page_list+0x12e/0x9b0 mm/page_alloc.c:3443
 release_pages+0xe38/0xe80 mm/swap.c:1103
 __pagevec_release+0x71/0xe0 mm/swap.c:1123
 pagevec_release include/linux/pagevec.h:88 [inline]
 truncate_inode_pages_range+0x771/0x15b0 mm/truncate.c:367
 truncate_inode_pages mm/truncate.c:473 [inline]
 truncate_inode_pages_final+0xc0/0xd0 mm/truncate.c:524
 ext4_evict_inode+0x3b8/0x1760 fs/ext4/inode.c:225
 evict+0x478/0x910 fs/inode.c:612
 iput_final fs/inode.c:1736 [inline]
 iput+0x638/0x7c0 fs/inode.c:1762
 dentry_unlink_inode+0x2cf/0x380 fs/dcache.c:378
 __dentry_kill+0x44f/0x650 fs/dcache.c:583
 dentry_kill+0xc0/0x2a0 fs/dcache.c:-1
 dput+0x42/0x80 fs/dcache.c:883
 __fput+0x4fe/0x770 fs/file_table.c:294
 ____fput+0x15/0x20 fs/file_table.c:314
 task_work_run+0x127/0x190 kernel/task_work.c:189

Memory state around the buggy address:
 ffff888156fb2f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888156fb2f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888156fb3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888156fb3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888156fb3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs (loop9): Delayed block allocation failed for inode 15 at logical offset 203 with max blocks 1 with error 117
EXT4-fs (loop9): This should not happen!! Data will be lost