==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbfb/0xe30 fs/ext4/extents.c:945
Read of size 4 at addr ffff8881363e2e80 by task syz.5.1021/4578

CPU: 0 PID: 4578 Comm: syz.5.1021 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x1a7/0x208 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0x100/0x140 mm/kasan/report.c:452
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report_generic.c:308
 ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
 ext4_find_extent+0xbfb/0xe30 fs/ext4/extents.c:945
 ext4_ext_map_blocks+0x204/0x5da0 fs/ext4/extents.c:4191
 ext4_map_blocks+0x979/0x1b10 fs/ext4/inode.c:676
 mpage_map_one_extent fs/ext4/inode.c:2454 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2507 [inline]
 ext4_writepages+0x1238/0x2f00 fs/ext4/inode.c:2875
 do_writepages+0x12e/0x280 mm/page-writeback.c:2380
 __filemap_fdatawrite_range+0x2a0/0x350 mm/filemap.c:427
 filemap_write_and_wait_range+0x65/0x270 mm/filemap.c:660
 ext4_collapse_range fs/ext4/extents.c:5430 [inline]
 ext4_fallocate+0xc77/0x1a60 fs/ext4/extents.c:4794
 vfs_fallocate+0x4b9/0x590 fs/open.c:310
 ksys_fallocate fs/open.c:333 [inline]
 __do_sys_fallocate fs/open.c:341 [inline]
 __se_sys_fallocate fs/open.c:339 [inline]
 __x64_sys_fallocate+0xc0/0x110 fs/open.c:339
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f3174c22159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f317367b028 EFLAGS: 00000246 ORIG_RAX: 000000000000011d
RAX: ffffffffffffffda RBX: 00007f3174ea9fa0 RCX: 00007f3174c22159
RDX: 0000000000004000 RSI: 0000000000000008 RDI: 000000000000000a
RBP: 00007f3174cb9024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000008000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f3174eaa038 R14: 00007f3174ea9fa0 R15: 00007ffd6d050c38

The buggy address belongs to the page:
page:ffffea0004d8f880 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x1363e2
flags: 0x4000000000000000()
raw: 4000000000000000 dead000000000100 dead000000000122 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 0x100cca(GFP_HIGHUSER_MOVABLE), pid 4412, ts 146849651713, free_ts 147675932240
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x176/0x190 mm/page_alloc.c:2462
 get_page_from_freelist+0x225f/0x23f0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x29a/0x640 mm/page_alloc.c:5384
 __alloc_pages include/linux/gfp.h:544 [inline]
 __alloc_pages_node include/linux/gfp.h:557 [inline]
 alloc_pages_node include/linux/gfp.h:571 [inline]
 alloc_pages include/linux/gfp.h:590 [inline]
 shmem_alloc_page+0x1fd/0x380 mm/shmem.c:1580
 shmem_alloc_and_acct_page+0x3d3/0x840 mm/shmem.c:1605
 shmem_getpage_gfp+0x785/0x20f0 mm/shmem.c:1918
 shmem_getpage mm/shmem.c:161 [inline]
 shmem_write_begin+0xce/0x1b0 mm/shmem.c:2497
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 __generic_file_write_iter+0x24b/0x480 mm/filemap.c:3638
 generic_file_write_iter+0xa9/0x1d0 mm/filemap.c:3670
 call_write_iter include/linux/fs.h:2072 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x770/0xd70 fs/read_write.c:605
 ksys_write+0x14a/0x260 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:28 [inline]
 free_pages_prepare mm/page_alloc.c:1349 [inline]
 free_pcp_prepare mm/page_alloc.c:1421 [inline]
 free_unref_page_prepare+0x2b7/0x2d0 mm/page_alloc.c:3336
 free_unref_page_list+0x129/0x9c0 mm/page_alloc.c:3443
 release_pages+0xe41/0xe90 mm/swap.c:1103
 __pagevec_release+0x71/0xe0 mm/swap.c:1123
 pagevec_release include/linux/pagevec.h:88 [inline]
 shmem_undo_range+0x741/0x1740 mm/shmem.c:965
 shmem_truncate_range mm/shmem.c:1069 [inline]
 shmem_evict_inode+0x1dc/0x970 mm/shmem.c:1169
 evict+0x4a9/0x940 fs/inode.c:612
 iput_final fs/inode.c:1736 [inline]
 iput+0x654/0x7e0 fs/inode.c:1762
 do_unlinkat+0x347/0x670 fs/namei.c:4092
 __do_sys_unlink fs/namei.c:4132 [inline]
 __se_sys_unlink fs/namei.c:4130 [inline]
 __x64_sys_unlink+0x49/0x50 fs/namei.c:4130
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Memory state around the buggy address:
 ffff8881363e2d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881363e2e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881363e2e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                   ^
 ffff8881363e2f00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881363e2f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================
EXT4-fs error (device loop5): __ext4_get_inode_loc:4451: comm syz.5.1021: Invalid inode table block 13816973012072644543 in block_group 0
EXT4-fs error (device loop5) in ext4_reserve_inode_write:5971: Corrupt filesystem
EXT4-fs error (device loop5): ext4_dirty_inode:6181: inode #15: comm syz.5.1021: mark_inode_dirty error
EXT4-fs error (device loop5): __ext4_get_inode_loc:4451: comm syz.5.1021: Invalid inode table block 13816973012072644543 in block_group 0
EXT4-fs error (device loop5) in ext4_reserve_inode_write:5971: Corrupt filesystem
EXT4-fs error (device loop5): ext4_dirty_inode:6181: inode #15: comm syz.5.1021: mark_inode_dirty error
EXT4-fs (loop5): Delayed block allocation failed for inode 15 at logical offset 131075 with max blocks 13 with error 117
EXT4-fs (loop5): This should not happen!! Data will be lost