==================================================================
BUG: KASAN: use-after-free in ext4_ext_binsearch fs/ext4/extents.c:826 [inline]
BUG: KASAN: use-after-free in ext4_find_extent+0xbeb/0xe20 fs/ext4/extents.c:945
Read of size 4 at addr ffff8881178ee018 by task kworker/u4:2/49

CPU: 1 PID: 49 Comm: kworker/u4:2 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Workqueue: writeback wb_workfn (flush-7:9)
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 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+0xe2/0x130 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+0xbeb/0xe20 fs/ext4/extents.c:945
 ext4_ext_map_blocks+0x1de/0x5d40 fs/ext4/extents.c:4160
 ext4_map_blocks+0x978/0x1bc0 fs/ext4/inode.c:674
 mpage_map_one_extent fs/ext4/inode.c:2452 [inline]
 mpage_map_and_submit_extent fs/ext4/inode.c:2505 [inline]
 ext4_writepages+0x11d5/0x2e00 fs/ext4/inode.c:2873
 do_writepages+0x12a/0x270 mm/page-writeback.c:2380
 __writeback_single_inode+0xd5/0xa20 fs/fs-writeback.c:1470
 writeback_sb_inodes+0x860/0x1400 fs/fs-writeback.c:1733
 wb_writeback+0x3e3/0xb90 fs/fs-writeback.c:1908
 wb_do_writeback fs/fs-writeback.c:2053 [inline]
 wb_workfn+0x38f/0xe20 fs/fs-writeback.c:2094
 process_one_work+0x6e1/0xba0 kernel/workqueue.c:2301
 worker_thread+0xa6a/0x13b0 kernel/workqueue.c:2447
 kthread+0x346/0x3d0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Allocated by task 12837:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:430 [inline]
 __kasan_slab_alloc+0xbd/0xf0 mm/kasan/common.c:463
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2947 [inline]
 slab_alloc mm/slub.c:2955 [inline]
 kmem_cache_alloc+0x165/0x2e0 mm/slub.c:2960
 getname_flags+0xb9/0x500 fs/namei.c:141
 user_path_at_empty+0x2f/0x50 fs/namei.c:2740
 user_path_at include/linux/namei.h:60 [inline]
 __do_sys_chdir fs/open.c:492 [inline]
 __se_sys_chdir+0x91/0x210 fs/open.c:486
 __x64_sys_chdir+0x38/0x40 fs/open.c:486
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 12837:
 kasan_save_stack mm/kasan/common.c:38 [inline]
 kasan_set_track+0x4a/0x70 mm/kasan/common.c:45
 kasan_set_free_info+0x23/0x40 mm/kasan/generic.c:370
 ____kasan_slab_free+0x125/0x160 mm/kasan/common.c:362
 __kasan_slab_free+0x11/0x20 mm/kasan/common.c:370
 kasan_slab_free include/linux/kasan.h:220 [inline]
 slab_free_hook mm/slub.c:1595 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1621
 slab_free mm/slub.c:3203 [inline]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3219
 putname fs/namei.c:262 [inline]
 filename_lookup+0x459/0x600 fs/namei.c:2470
 user_path_at_empty+0x43/0x50 fs/namei.c:2740
 user_path_at include/linux/namei.h:60 [inline]
 __do_sys_chdir fs/open.c:492 [inline]
 __se_sys_chdir+0x91/0x210 fs/open.c:486
 __x64_sys_chdir+0x38/0x40 fs/open.c:486
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

The buggy address belongs to the object at ffff8881178ed500
 which belongs to the cache names_cache of size 4096
The buggy address is located 2840 bytes inside of
 4096-byte region [ffff8881178ed500, ffff8881178ee500)
The buggy address belongs to the page:
page:ffffea00045e3a00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1178e8
head:ffffea00045e3a00 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff88810018af00
raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 701, ts 419883567980, free_ts 419875108892
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1808 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1869
 new_slab_objects mm/slub.c:2627 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2791
 __slab_alloc+0x63/0xa0 mm/slub.c:2831
 slab_alloc_node mm/slub.c:2913 [inline]
 slab_alloc mm/slub.c:2955 [inline]
 kmem_cache_alloc+0x1af/0x2e0 mm/slub.c:2960
 getname_flags+0xb9/0x500 fs/namei.c:141
 user_path_at_empty+0x2f/0x50 fs/namei.c:2740
 user_path_at include/linux/namei.h:60 [inline]
 vfs_statx+0xff/0x520 fs/stat.c:193
 vfs_fstatat fs/stat.c:215 [inline]
 __do_sys_newfstatat fs/stat.c:383 [inline]
 __se_sys_newfstatat+0xc6/0x340 fs/stat.c:377
 __x64_sys_newfstatat+0x9b/0xb0 fs/stat.c:377
 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_pages_ok+0x7fc/0x820 mm/page_alloc.c:1629
 free_the_page mm/page_alloc.c:5431 [inline]
 __free_pages+0xdd/0x380 mm/page_alloc.c:5440
 __free_slab+0xcf/0x190 mm/slub.c:1894
 free_slab mm/slub.c:1909 [inline]
 discard_slab mm/slub.c:1915 [inline]
 unfreeze_partials+0x15f/0x190 mm/slub.c:2410
 put_cpu_partial+0xc1/0x180 mm/slub.c:2446
 __slab_free+0x2c9/0x3a0 mm/slub.c:3095
 do_slab_free mm/slub.c:3191 [inline]
 ___cache_free+0x111/0x130 mm/slub.c:3210
 qlink_free+0x50/0x90 mm/kasan/quarantine.c:157
 qlist_free_all+0x5f/0xb0 mm/kasan/quarantine.c:176
 kasan_quarantine_reduce+0x14a/0x160 mm/kasan/quarantine.c:283
 __kasan_slab_alloc+0x2f/0xf0 mm/kasan/common.c:440
 kasan_slab_alloc include/linux/kasan.h:244 [inline]
 slab_post_alloc_hook+0x5d/0x2f0 mm/slab.h:580
 slab_alloc_node mm/slub.c:2947 [inline]
 slab_alloc mm/slub.c:2955 [inline]
 kmem_cache_alloc+0x165/0x2e0 mm/slub.c:2960
 getname_flags+0xb9/0x500 fs/namei.c:141
 getname+0x19/0x20 fs/namei.c:212
 do_sys_openat2+0xd9/0x6d0 fs/open.c:1211

Memory state around the buggy address:
 ffff8881178edf00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881178edf80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881178ee000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                            ^
 ffff8881178ee080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881178ee100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
EXT4-fs error (device loop9): ext4_map_blocks:740: inode #15: block 395414420: comm kworker/u4:2: lblock 52 mapped to illegal pblock 395414420 (length 12)
EXT4-fs (loop9): Delayed block allocation failed for inode 15 at logical offset 52 with max blocks 12 with error 117
EXT4-fs (loop9): This should not happen!! Data will be lost