==================================================================
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 ffff8881395d6018 by task kworker/u4:5/342

CPU: 0 PID: 342 Comm: kworker/u4:5 Not tainted 6.1.138-syzkaller-00046-gdb710ea87c32 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: writeback wb_workfn (flush-7:4)
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:ffffea0004e57580 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1395d6
flags: 0x4000000000000000(zone=1)
raw: 4000000000000000 ffffea0004e57588 ffffea0004e57588 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner info is not present (never set?)

Memory state around the buggy address:
 ffff8881395d5f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881395d5f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881395d6000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                            ^
 ffff8881395d6080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881395d6100: 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: 0 PID: 342 Comm: kworker/u4:5 Tainted: G    B              6.1.138-syzkaller-00046-gdb710ea87c32 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: writeback wb_workfn (flush-7:4)
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 50 17 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 9f be 86 ff <0f> 0b e8 98 be 86 ff eb 2f e8 91 be 86 ff eb 69 e8 8a be 86 ff 31
RSP: 0018:ffffc9000dcdf120 EFLAGS: 00010293
RAX: ffffffff81e93271 RBX: 0000000000000000 RCX: ffff888113cfe540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000dcdf490 R08: dffffc0000000000 R09: ffffed10200b2c4d
R10: ffffed10200b2c4d R11: 1ffff110200b2c4c R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8881005962a0 R15: 000000000000042b
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c2f329e CR3: 00000001332f5000 CR4: 00000000003506b0
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 50 17 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 9f be 86 ff <0f> 0b e8 98 be 86 ff eb 2f e8 91 be 86 ff eb 69 e8 8a be 86 ff 31
RSP: 0018:ffffc9000dcdf120 EFLAGS: 00010293
RAX: ffffffff81e93271 RBX: 0000000000000000 RCX: ffff888113cfe540
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc9000dcdf490 R08: dffffc0000000000 R09: ffffed10200b2c4d
R10: ffffed10200b2c4d R11: 1ffff110200b2c4c R12: dffffc0000000000
R13: 0000000000000000 R14: ffff8881005962a0 R15: 000000000000042b
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f677f38fd58 CR3: 000000011277f000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400