==================================================================
BUG: KASAN: use-after-free in ext4_ext_insert_extent+0x3c13/0x4530 fs/ext4/extents.c:2072
Read of size 4 at addr ffff888123dd94a4 by task kworker/u4:0/7

CPU: 0 PID: 7 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: ext4-rsv-conversion ext4_end_io_rsv_work
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_insert_extent+0x3c13/0x4530 fs/ext4/extents.c:2072
 ext4_split_extent_at+0x79f/0xe90 fs/ext4/extents.c:3230
 ext4_split_extent+0x1d7/0x4e0 fs/ext4/extents.c:3349
 ext4_split_convert_extents fs/ext4/extents.c:3709 [inline]
 ext4_convert_unwritten_extents_endio fs/ext4/extents.c:3745 [inline]
 ext4_ext_handle_unwritten_extents fs/ext4/extents.c:3892 [inline]
 ext4_ext_map_blocks+0x2459/0x5d40 fs/ext4/extents.c:4225
 ext4_map_blocks+0x978/0x1bc0 fs/ext4/inode.c:674
 ext4_convert_unwritten_extents+0x21c/0x3f0 fs/ext4/extents.c:4862
 ext4_convert_unwritten_io_end_vec+0x103/0x180 fs/ext4/extents.c:4901
 ext4_end_io_end fs/ext4/page-io.c:189 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:262 [inline]
 ext4_end_io_rsv_work+0x2b9/0x600 fs/ext4/page-io.c:276
 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:ffffea00048f7640 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x123dd9
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 496, ts 42531663177, free_ts 42753329338
 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_da_write_begin+0x53c/0xe80 fs/ext4/inode.c:3067
 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
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_write+0x140/0x240 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
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
 do_unlinkat+0x33f/0x670 fs/namei.c:4042
 __do_sys_unlink fs/namei.c:4082 [inline]
 __se_sys_unlink fs/namei.c:4080 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4080
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff888123dd9380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888123dd9400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888123dd9480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                               ^
 ffff888123dd9500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888123dd9580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop4): ext4_ext_split:1073: inode #19: comm kworker/u4:0: p_ext > EXT_MAX_EXTENT!
EXT4-fs warning (device loop4): ext4_convert_unwritten_extents:4869: inode #19: block 17: len 1: ext4_ext_map_blocks returned -117
EXT4-fs error (device loop4): __ext4_get_inode_loc:4438: comm kworker/u4:0: Invalid inode table block 34360905424 in block_group 0
EXT4-fs error (device loop4) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs error (device loop4): ext4_convert_unwritten_extents:4870: inode #19: comm kworker/u4:0: mark_inode_dirty error
EXT4-fs (loop4): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop4): ext4_convert_unwritten_extents:4869: inode #19: block 18: len 1: ext4_ext_map_blocks returned -28
EXT4-fs error (device loop4): __ext4_get_inode_loc:4438: comm kworker/u4:0: Invalid inode table block 34360905424 in block_group 0
EXT4-fs error (device loop4) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs error (device loop4): ext4_convert_unwritten_extents:4870: inode #19: comm kworker/u4:0: mark_inode_dirty error
EXT4-fs (loop4): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -28)
EXT4-fs error (device loop4): __ext4_get_inode_loc:4438: comm kworker/u4:0: Invalid inode table block 34360905424 in block_group 0
EXT4-fs error (device loop4): __ext4_get_inode_loc:4438: comm kworker/u4:0: Invalid inode table block 34360905424 in block_group 0
EXT4-fs error (device loop5): ext4_find_extent:928: inode #19: comm kworker/u4:0: pblk 208 bad header/extent: invalid magic - magic 6f69, entries 29795, max 9324(0), depth 20297(0)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 15: len 1: ext4_ext_map_blocks returned -117
EXT4-fs error (device loop5): __ext4_get_inode_loc:4438: comm kworker/u4:0: Invalid inode table block 34360905424 in block_group 0
EXT4-fs error (device loop5) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs error (device loop5): ext4_convert_unwritten_extents:4870: inode #19: comm kworker/u4:0: mark_inode_dirty error
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs error (device loop5): ext4_find_extent:928: inode #19: comm kworker/u4:0: pblk 208 bad header/extent: invalid magic - magic 6f69, entries 29795, max 9324(0), depth 20297(0)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 16: len 1: ext4_ext_map_blocks returned -117
EXT4-fs error (device loop5): __ext4_get_inode_loc:4438: comm kworker/u4:0: Invalid inode table block 34360905424 in block_group 0
EXT4-fs error (device loop5) in ext4_reserve_inode_write:5933: Corrupt filesystem
EXT4-fs error (device loop5): ext4_convert_unwritten_extents:4870: inode #19: comm kworker/u4:0: mark_inode_dirty error
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs error (device loop5): ext4_find_extent:928: inode #19: comm kworker/u4:0: pblk 208 bad header/extent: invalid magic - magic 6f69, entries 29795, max 9324(0), depth 20297(0)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 17: len 1: ext4_ext_map_blocks returned -117
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 18: len 1: ext4_ext_map_blocks returned -117
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 19: len 1: ext4_ext_map_blocks returned -117
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 20: len 1: ext4_ext_map_blocks returned -117
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 21: len 1: ext4_ext_map_blocks returned -117
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 22: len 1: ext4_ext_map_blocks returned -117
EXT4-fs (loop5): failed to convert unwritten extents to written extents -- potential data loss!  (inode 19, error -117)
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 23: len 1: ext4_ext_map_blocks returned -117
EXT4-fs warning (device loop5): ext4_convert_unwritten_extents:4869: inode #19: block 24: len 1: ext4_ext_map_blocks returned -117