==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:946
Read of size 4 at addr ffff0000e1867314 by task kworker/u4:2/148

CPU: 0 PID: 148 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/03/2025
Workqueue: writeback wb_workfn (flush-7:0)
Call trace:
 dump_backtrace+0x0/0x43c arch/arm64/kernel/stacktrace.c:152
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:216
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf8/0x160 lib/dump_stack.c:106
 print_address_description+0x78/0x30c mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0xec/0x15c mm/kasan/report.c:451
 __asan_report_load4_noabort+0x44/0x50 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:827 [inline]
 ext4_find_extent+0x994/0xb6c fs/ext4/extents.c:946
 ext4_ext_map_blocks+0x230/0x5694 fs/ext4/extents.c:4166
 ext4_map_blocks+0x7b8/0x167c fs/ext4/inode.c:673
 mpage_map_one_extent fs/ext4/inode.c:2408 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2461 [inline]
 ext4_writepages+0xf00/0x2c14 fs/ext4/inode.c:2829
 do_writepages+0x36c/0x578 mm/page-writeback.c:2386
 __writeback_single_inode+0x148/0x11f0 fs/fs-writeback.c:1657
 writeback_sb_inodes+0x7fc/0x1378 fs/fs-writeback.c:1940
 wb_writeback+0x3d8/0xe44 fs/fs-writeback.c:2114
 wb_do_writeback fs/fs-writeback.c:2257 [inline]
 wb_workfn+0x350/0xdd8 fs/fs-writeback.c:2298
 process_one_work+0x79c/0x1140 kernel/workqueue.c:2310
 worker_thread+0x8f4/0x101c kernel/workqueue.c:2457
 kthread+0x374/0x454 kernel/kthread.c:334
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:856

The buggy address belongs to the page:
page:00000000b4960965 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x121867
flags: 0x5ffc00000000000(node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000000000 fffffc0003a18b08 fffffc0003a0b848 0000000000000000
raw: 0000000000000001 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000e1867200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e1867280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff0000e1867300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                         ^
 ffff0000e1867380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff0000e1867400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop0): ext4_map_blocks:739: inode #15: comm kworker/u4:2: lblock 0 mapped to illegal pblock 0 (length 1)
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs error (device loop0): ext4_map_blocks:739: inode #15: block 86110555277147: comm kworker/u4:2: lblock 0 mapped to illegal pblock 86110555277147 (length 1)
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs error (device loop0): ext4_ext_split:1074: inode #15: comm kworker/u4:2: p_ext > EXT_MAX_EXTENT!
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs error (device loop0): ext4_ext_split:1146: inode #15: comm kworker/u4:2: eh_entries 26982 != eh_max 25964!
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs error (device loop0): ext4_map_blocks:739: inode #15: block 2014339661824: comm kworker/u4:2: lblock 0 mapped to illegal pblock 2014339661824 (length 1)
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs error (device loop0): ext4_map_blocks:739: inode #15: block 71748523475265: comm kworker/u4:2: lblock 0 mapped to illegal pblock 71748523475265 (length 1)
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost

EXT4-fs error (device loop0): ext4_map_blocks:739: inode #15: block 126969739568179: comm kworker/u4:2: lblock 0 mapped to illegal pblock 126969739568179 (length 1)
EXT4-fs (loop0): Delayed block allocation failed for inode 15 at logical offset 0 with max blocks 1 with error 117
EXT4-fs (loop0): This should not happen!! Data will be lost