==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:837 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953
Read of size 4 at addr ffff88812bb2ee18 by task kworker/u4:4/475

CPU: 1 PID: 475 Comm: kworker/u4:4 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: writeback wb_workfn (flush-7:2)
Call Trace:
 <TASK>
 __dump_stack+0x21/0x24 lib/dump_stack.c:88
 dump_stack_lvl+0xee/0x150 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_binsearch fs/ext4/extents.c:837 [inline]
 ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:953
 ext4_ext_map_blocks+0x1dc/0x6060 fs/ext4/extents.c:4166
 ext4_map_blocks+0x9cb/0x1b60 fs/ext4/inode.c:679
 mpage_map_one_extent fs/ext4/inode.c:2435 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2488 [inline]
 ext4_writepages+0x1260/0x3020 fs/ext4/inode.c:2856
 do_writepages+0x3a9/0x5e0 mm/page-writeback.c:2494
 __writeback_single_inode+0xc6/0xad0 fs/fs-writeback.c:1612
 writeback_sb_inodes+0x9b8/0x1550 fs/fs-writeback.c:1903
 wb_writeback+0x3f1/0x980 fs/fs-writeback.c:2079
 wb_do_writeback fs/fs-writeback.c:2226 [inline]
 wb_workfn+0x350/0xda0 fs/fs-writeback.c:2266
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2449
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>

The buggy address belongs to the physical page:
page:ffffea0004aecb80 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x12bb2e
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004aecbc8 ffffea0004aeab08 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 0x8140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO|__GFP_CMA), pid 286, tgid 283 (syz-execprog), ts 25839967427, free_ts 27772786421
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2643
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2650
 get_page_from_freelist+0x2c7b/0x2cf0 mm/page_alloc.c:4554
 __alloc_pages+0x1c3/0x450 mm/page_alloc.c:5868
 __folio_alloc+0x12/0x40 mm/page_alloc.c:5900
 __folio_alloc_node include/linux/gfp.h:245 [inline]
 folio_alloc include/linux/gfp.h:274 [inline]
 alloc_page_vma include/linux/gfp.h:283 [inline]
 do_anonymous_page mm/memory.c:4283 [inline]
 handle_pte_fault mm/memory.c:5169 [inline]
 __handle_mm_fault mm/memory.c:5313 [inline]
 handle_mm_fault+0x18ef/0x2640 mm/memory.c:5453
 do_user_addr_fault+0x905/0x1050 arch/x86/mm/fault.c:1323
 handle_page_fault arch/x86/mm/fault.c:1466 [inline]
 exc_page_fault+0x51/0xb0 arch/x86/mm/fault.c:1522
 asm_exc_page_fault+0x27/0x30 arch/x86/include/asm/idtentry.h:608
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1551 [inline]
 free_pcp_prepare mm/page_alloc.c:1625 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3589
 free_unref_page_list+0x112/0x8b0 mm/page_alloc.c:3740
 release_pages+0xad1/0xb20 mm/swap.c:1043
 free_pages_and_swap_cache+0x86/0xa0 mm/swap_state.c:315
 tlb_batch_pages_flush mm/mmu_gather.c:59 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:254 [inline]
 tlb_flush_mmu+0x101/0x1e0 mm/mmu_gather.c:261
 zap_pte_range mm/memory.c:1547 [inline]
 zap_pmd_range mm/memory.c:1596 [inline]
 zap_pud_range mm/memory.c:1625 [inline]
 zap_p4d_range mm/memory.c:1646 [inline]
 unmap_page_range+0x20c6/0x2310 mm/memory.c:1667
 unmap_single_vma mm/memory.c:1713 [inline]
 unmap_vmas+0x31c/0x430 mm/memory.c:1753
 exit_mmap+0x268/0xb60 mm/mmap.c:3369
 __mmput+0x93/0x320 kernel/fork.c:1300
 mmput+0x4b/0x150 kernel/fork.c:1323
 exit_mm kernel/exit.c:568 [inline]
 do_exit+0x981/0x2650 kernel/exit.c:873
 do_group_exit+0x210/0x2d0 kernel/exit.c:1028
 get_signal+0x13b5/0x1520 kernel/signal.c:2889
 arch_do_signal_or_restart+0xb0/0x1030 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x7a/0xb0 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0x5a/0xa0 kernel/entry/common.c:210

Memory state around the buggy address:
 ffff88812bb2ed00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812bb2ed80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88812bb2ee00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff88812bb2ee80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88812bb2ef00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop2): ext4_map_blocks:745: inode #15: block 120368058753396: comm kworker/u4:4: lblock 0 mapped to illegal pblock 120368058753396 (length 1)
EXT4-fs (loop2): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop2): This should not happen!! Data will be lost

------------[ cut here ]------------
kernel BUG at fs/ext4/inode.c:2447!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 475 Comm: kworker/u4:4 Tainted: G    B              syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: writeback wb_workfn (flush-7:2)
RIP: 0010:mpage_map_one_extent fs/ext4/inode.c:2447 [inline]
RIP: 0010:mpage_map_and_submit_extent fs/ext4/inode.c:2488 [inline]
RIP: 0010:ext4_writepages+0x2f61/0x3020 fs/ext4/inode.c:2856
Code: 08 48 89 df e8 30 f1 ca ff 48 8b 3b 48 8b 74 24 40 48 8b 54 24 30 48 8b 4c 24 20 45 89 f0 e8 86 c7 07 00 eb 5b e8 1f 83 86 ff <0f> 0b e8 18 83 86 ff eb 2f e8 11 83 86 ff eb 69 e8 0a 83 86 ff 31
RSP: 0018:ffffc90000aa7120 EFLAGS: 00010293
RAX: ffffffff81e99ae1 RBX: 0000000000000000 RCX: ffff88811bc8e540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000aa7490 R08: dffffc0000000000 R09: ffffed1024e06302
R10: ffffed1024e06302 R11: 1ffff11024e06301 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888127031848 R15: 000000000000042b
FS:  0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000f000 CR3: 0000000114686000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 do_writepages+0x3a9/0x5e0 mm/page-writeback.c:2494
 __writeback_single_inode+0xc6/0xad0 fs/fs-writeback.c:1612
 writeback_sb_inodes+0x9b8/0x1550 fs/fs-writeback.c:1903
 wb_writeback+0x3f1/0x980 fs/fs-writeback.c:2079
 wb_do_writeback fs/fs-writeback.c:2226 [inline]
 wb_workfn+0x350/0xda0 fs/fs-writeback.c:2266
 process_one_work+0x71f/0xc40 kernel/workqueue.c:2302
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2449
 kthread+0x281/0x320 kernel/kthread.c:386
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:mpage_map_one_extent fs/ext4/inode.c:2447 [inline]
RIP: 0010:mpage_map_and_submit_extent fs/ext4/inode.c:2488 [inline]
RIP: 0010:ext4_writepages+0x2f61/0x3020 fs/ext4/inode.c:2856
Code: 08 48 89 df e8 30 f1 ca ff 48 8b 3b 48 8b 74 24 40 48 8b 54 24 30 48 8b 4c 24 20 45 89 f0 e8 86 c7 07 00 eb 5b e8 1f 83 86 ff <0f> 0b e8 18 83 86 ff eb 2f e8 11 83 86 ff eb 69 e8 0a 83 86 ff 31
RSP: 0018:ffffc90000aa7120 EFLAGS: 00010293
RAX: ffffffff81e99ae1 RBX: 0000000000000000 RCX: ffff88811bc8e540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000aa7490 R08: dffffc0000000000 R09: ffffed1024e06302
R10: ffffed1024e06302 R11: 1ffff11024e06301 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888127031848 R15: 000000000000042b
FS:  0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000020000000f000 CR3: 0000000114686000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400