==================================================================
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 ffff888126817e18 by task kworker/u4:4/308

CPU: 0 PID: 308 Comm: kworker/u4:4 Not tainted 6.1.141-syzkaller-1169944-gfa7e0538663e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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+0x71/0x210 mm/kasan/report.c:316
 print_report+0x4a/0x60 mm/kasan/report.c:427
 kasan_report+0x122/0x150 mm/kasan/report.c:531
 __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:4165
 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:2299
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2446
 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:ffffea00049a05c0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x126817
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x102dc2(GFP_HIGHUSER|__GFP_NOWARN|__GFP_ZERO), pid 427, tgid 427 (syz-executor), ts 54180902473, free_ts 54298910935
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0x1f5/0x210 mm/page_alloc.c:2637
 prep_new_page+0x1c/0x110 mm/page_alloc.c:2644
 get_page_from_freelist+0x2c7b/0x2cf0 mm/page_alloc.c:4539
 __alloc_pages+0x19e/0x3a0 mm/page_alloc.c:5850
 vm_area_alloc_pages mm/vmalloc.c:-1 [inline]
 __vmalloc_area_node mm/vmalloc.c:3074 [inline]
 __vmalloc_node_range+0x891/0x13d0 mm/vmalloc.c:3246
 vmalloc_user+0x73/0x80 mm/vmalloc.c:3400
 kcov_ioctl+0x57/0x640 kernel/kcov.c:713
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl+0x12f/0x1b0 fs/ioctl.c:856
 __x64_sys_ioctl+0x7b/0x90 fs/ioctl.c:856
 x64_sys_call+0x58b/0x9a0 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 free_pages_prepare mm/page_alloc.c:1545 [inline]
 free_pcp_prepare mm/page_alloc.c:1619 [inline]
 free_unref_page_prepare+0x742/0x750 mm/page_alloc.c:3581
 free_unref_page+0x8f/0x530 mm/page_alloc.c:3677
 free_the_page mm/page_alloc.c:830 [inline]
 __free_pages+0x67/0x100 mm/page_alloc.c:5939
 __vunmap+0x9af/0xb70 mm/vmalloc.c:2729
 __vfree mm/vmalloc.c:2778 [inline]
 vfree+0x61/0x90 mm/vmalloc.c:2809
 kcov_put kernel/kcov.c:437 [inline]
 kcov_close+0x2b/0x50 kernel/kcov.c:533
 __fput+0x1fc/0x8f0 fs/file_table.c:320
 ____fput+0x15/0x20 fs/file_table.c:348
 task_work_run+0x1db/0x240 kernel/task_work.c:203
 exit_task_work include/linux/task_work.h:39 [inline]
 do_exit+0xa1d/0x2650 kernel/exit.c:877
 do_group_exit+0x210/0x2d0 kernel/exit.c:1027
 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
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x1a/0x30 kernel/entry/common.c:303

Memory state around the buggy address:
 ffff888126817d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888126817d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888126817e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff888126817e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888126817f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
------------[ cut here ]------------
kernel BUG at fs/ext4/inode.c:2447!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 308 Comm: kworker/u4:4 Tainted: G    B              6.1.141-syzkaller-1169944-gfa7e0538663e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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 c0 0e cb ff 48 8b 3b 48 8b 74 24 40 48 8b 54 24 30 48 8b 4c 24 20 45 89 f0 e8 46 c8 07 00 eb 5b e8 cf b4 86 ff <0f> 0b e8 c8 b4 86 ff eb 2f e8 c1 b4 86 ff eb 69 e8 ba b4 86 ff 31
RSP: 0018:ffffc900032c7120 EFLAGS: 00010293
RAX: ffffffff81e942a1 RBX: 0000000000000000 RCX: ffff888108305100
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900032c7490 R08: dffffc0000000000 R09: ffffed1020e32f29
R10: ffffed1020e32f29 R11: 1ffff11020e32f28 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888107197980 R15: 000000000000042b
FS:  0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f0b9af21130 CR3: 0000000006e0f000 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:2299
 worker_thread+0xa29/0x11f0 kernel/workqueue.c:2446
 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 c0 0e cb ff 48 8b 3b 48 8b 74 24 40 48 8b 54 24 30 48 8b 4c 24 20 45 89 f0 e8 46 c8 07 00 eb 5b e8 cf b4 86 ff <0f> 0b e8 c8 b4 86 ff eb 2f e8 c1 b4 86 ff eb 69 e8 ba b4 86 ff 31
RSP: 0018:ffffc900032c7120 EFLAGS: 00010293
RAX: ffffffff81e942a1 RBX: 0000000000000000 RCX: ffff888108305100
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc900032c7490 R08: dffffc0000000000 R09: ffffed1020e32f29
R10: ffffed1020e32f29 R11: 1ffff11020e32f28 R12: dffffc0000000000
R13: 0000000000000000 R14: ffff888107197980 R15: 000000000000042b
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c005859000 CR3: 000000012d0e5000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400