syzbot

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BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbea/0xe30 fs/ext4/extents.c:946
Read of size 4 at addr ffff88812324ec14 by task kworker/u4:0/8

CPU: 0 PID: 8 Comm: kworker/u4:0 Not tainted 5.15.178-syzkaller-00034-g5e1b899f19c3 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: writeback wb_workfn (flush-7:4)
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x151/0x1c0 lib/dump_stack.c:106
 print_address_description+0x87/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:427 [inline]
 kasan_report+0x179/0x1c0 mm/kasan/report.c:444
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0xbea/0xe30 fs/ext4/extents.c:946
 ext4_ext_map_blocks+0x269/0x7450 fs/ext4/extents.c:4165
 ext4_map_blocks+0xa60/0x1c70 fs/ext4/inode.c:673
 mpage_map_one_extent fs/ext4/inode.c:2420 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2473 [inline]
 ext4_writepages+0x1628/0x4000 fs/ext4/inode.c:2841
 do_writepages+0x40e/0x670 mm/page-writeback.c:2388
 __writeback_single_inode+0xdf/0xa70 fs/fs-writeback.c:1647
 writeback_sb_inodes+0xb2a/0x1920 fs/fs-writeback.c:1930
 __writeback_inodes_wb+0x118/0x3f0 fs/fs-writeback.c:2001
 wb_writeback+0x3da/0x9f0 fs/fs-writeback.c:2108
 wb_check_background_flush fs/fs-writeback.c:2178 [inline]
 wb_do_writeback fs/fs-writeback.c:2266 [inline]
 wb_workfn+0xc12/0x1110 fs/fs-writeback.c:2294
 process_one_work+0x6bb/0xc10 kernel/workqueue.c:2325
 worker_thread+0xad5/0x12a0 kernel/workqueue.c:2472
 kthread+0x421/0x510 kernel/kthread.c:337
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

The buggy address belongs to the page:
page:ffffea00048c9380 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12324e
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea00048c93c8 ffffea00048c9348 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 538, ts 30453639745, free_ts 30574608672
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1a3/0x1b0 mm/page_alloc.c:2605
 prep_new_page+0x1b/0x110 mm/page_alloc.c:2611
 get_page_from_freelist+0x3550/0x35d0 mm/page_alloc.c:4485
 __alloc_pages+0x27e/0x8f0 mm/page_alloc.c:5780
 __alloc_pages_node include/linux/gfp.h:591 [inline]
 alloc_pages_node include/linux/gfp.h:605 [inline]
 alloc_pages include/linux/gfp.h:618 [inline]
 __page_cache_alloc include/linux/pagemap.h:305 [inline]
 pagecache_get_page+0xb18/0xeb0 mm/filemap.c:1946
 grab_cache_page_write_begin+0x5d/0xa0 mm/filemap.c:3811
 ext4_da_write_begin+0x5ae/0xc30 fs/ext4/inode.c:3014
 generic_perform_write+0x2de/0x750 mm/filemap.c:3857
 ext4_buffered_write_iter+0x48a/0x610 fs/ext4/file.c:270
 ext4_file_write_iter+0x454/0x1660 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2204 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0xd5d/0x1110 fs/read_write.c:594
 ksys_write+0x199/0x2c0 fs/read_write.c:647
 __do_sys_write fs/read_write.c:659 [inline]
 __se_sys_write fs/read_write.c:656 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:656
 x64_sys_call+0x2f/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1472 [inline]
 free_pcp_prepare mm/page_alloc.c:1544 [inline]
 free_unref_page_prepare+0x7c8/0x7d0 mm/page_alloc.c:3534
 free_unref_page_list+0x14b/0xa60 mm/page_alloc.c:3671
 release_pages+0x1310/0x1370 mm/swap.c:1009
 __pagevec_release+0x84/0x100 mm/swap.c:1029
 pagevec_release include/linux/pagevec.h:81 [inline]
 truncate_inode_pages_range+0x482/0x1160 mm/truncate.c:329
 truncate_inode_pages mm/truncate.c:425 [inline]
 truncate_pagecache+0x6c/0x90 mm/truncate.c:735
 ext4_setattr+0xe4a/0x1940 fs/ext4/inode.c:5578
 notify_change+0xc7a/0xf30 fs/attr.c:505
 do_truncate+0x21c/0x300 fs/open.c:66
 handle_truncate fs/namei.c:3265 [inline]
 do_open fs/namei.c:3612 [inline]
 path_openat+0x28ed/0x2f40 fs/namei.c:3742
 do_filp_open+0x21c/0x460 fs/namei.c:3769
 do_sys_openat2+0x13f/0x820 fs/open.c:1234
 do_sys_open fs/open.c:1250 [inline]
 __do_sys_openat fs/open.c:1266 [inline]
 __se_sys_openat fs/open.c:1261 [inline]
 __x64_sys_openat+0x243/0x290 fs/open.c:1261
 x64_sys_call+0x6bf/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0

Memory state around the buggy address:
 ffff88812324eb00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812324eb80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812324ec00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff88812324ec80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812324ed00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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