==================================================================
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 ffff8881278261c8 by task kworker/u4:3/357

CPU: 0 PID: 357 Comm: kworker/u4:3 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: writeback wb_workfn (flush-7:2)
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
 __writeback_single_inode+0xd9/0xa30 fs/fs-writeback.c:1470
 writeback_sb_inodes+0x96d/0x1680 fs/fs-writeback.c:1733
 wb_writeback+0x40f/0xb80 fs/fs-writeback.c:1908
 wb_do_writeback fs/fs-writeback.c:2053 [inline]
 wb_workfn+0x3ac/0xf30 fs/fs-writeback.c:2094
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298

Allocated by task 300:
 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_kmalloc mm/kasan/common.c:509 [inline]
 __kasan_kmalloc+0xd4/0x100 mm/kasan/common.c:518
 kasan_kmalloc include/linux/kasan.h:254 [inline]
 kmem_cache_alloc_trace+0x179/0x2e0 mm/slub.c:2979
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 kernfs_iop_get_link+0x66/0x600 fs/kernfs/symlink.c:136
 pick_link+0x5b2/0xcc0 fs/namei.c:-1
 step_into+0xaa6/0xcd0 fs/namei.c:1816
 open_last_lookups fs/namei.c:3348 [inline]
 path_openat+0xec4/0x3040 fs/namei.c:3514
 do_filp_open+0x1df/0x400 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb

Freed by task 300:
 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:1600 [inline]
 slab_free_freelist_hook+0xc5/0x190 mm/slub.c:1626
 slab_free mm/slub.c:3208 [inline]
 kfree+0xc0/0x270 mm/slub.c:4196
 kfree_link+0x15/0x20 fs/libfs.c:1220
 do_delayed_call include/linux/delayed_call.h:28 [inline]
 put_link fs/namei.c:1024 [inline]
 open_last_lookups fs/namei.c:3347 [inline]
 path_openat+0xdec/0x3040 fs/namei.c:3514
 do_filp_open+0x1df/0x400 fs/namei.c:3544
 do_sys_openat2+0x19f/0x750 fs/open.c:1219
 do_sys_open fs/open.c:1235 [inline]
 __do_sys_openat fs/open.c:1251 [inline]
 __se_sys_openat fs/open.c:1246 [inline]
 __x64_sys_openat+0x136/0x160 fs/open.c:1246
 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 ffff888127826000
 which belongs to the cache kmalloc-4k of size 4096
The buggy address is located 456 bytes inside of
 4096-byte region [ffff888127826000, ffff888127827000)
The buggy address belongs to the page:
page:ffffea00049e0800 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x127820
head:ffffea00049e0800 order:3 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 dead000000000100 dead000000000122 ffff888100042c00
raw: 0000000000000000 0000000000040004 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 300, ts 26807419196, free_ts 0
 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_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2f8/0x4c0 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc_trace+0x1a8/0x2e0 mm/slub.c:2977
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:667 [inline]
 uevent_show+0x15d/0x340 drivers/base/core.c:2295
 dev_attr_show+0x56/0xd0 drivers/base/core.c:2002
 sysfs_kf_seq_show+0x266/0x3d0 fs/sysfs/file.c:61
 kernfs_seq_show+0x119/0x160 fs/kernfs/file.c:168
 seq_read_iter+0x472/0xce0 fs/seq_file.c:230
 kernfs_fop_read_iter+0x146/0x460 fs/kernfs/file.c:241
 call_read_iter include/linux/fs.h:2060 [inline]
 new_sync_read fs/read_write.c:415 [inline]
 vfs_read+0x62a/0xa50 fs/read_write.c:496
 ksys_read+0x14a/0x260 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888127826080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888127826100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888127826180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888127826200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888127826280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
EXT4-fs error (device loop2): __ext4_get_inode_loc:4451: comm kworker/u4:3: Invalid inode table block 11335476957231759676 in block_group 0
EXT4-fs error (device loop2): __ext4_get_inode_loc:4451: comm kworker/u4:3: Invalid inode table block 12251902480533084122 in block_group 0
EXT4-fs error (device loop2): __ext4_get_inode_loc:4451: comm kworker/u4:3: Invalid inode table block 4681120029152026812 in block_group 0
------------[ cut here ]------------
kernel BUG at fs/ext4/extents.c:2150!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 357 Comm: kworker/u4:3 Tainted: G    B             syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: writeback wb_workfn (flush-7:2)
RIP: 0010:ext4_ext_insert_extent+0x45b8/0x45f0 fs/ext4/extents.c:2150
Code: ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c 01 e9 ff ff 4c 89 f7 e8 09 5c d4 ff e9 f4 e8 ff ff e8 1f e7 99 ff 0f 0b e8 18 e7 99 ff <0f> 0b e8 11 e7 99 ff 0f 0b 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c fe
RSP: 0018:ffffc90000cc6b60 EFLAGS: 00010293
RAX: ffffffff81cabc48 RBX: ffff888122b7f000 RCX: ffff88810c644f00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000cc6d10 R08: ffff88811aa0049f R09: 1ffff11023540093
R10: dffffc0000000000 R11: ffffed1023540094 R12: ffff888122b8fbfc
R13: ffff888119ea0040 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f7100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555583146928 CR3: 000000010d6ef000 CR4: 00000000003506a0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 ext4_ext_map_blocks+0x16f2/0x5da0 fs/ext4/extents.c:4387
 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
 __writeback_single_inode+0xd9/0xa30 fs/fs-writeback.c:1470
 writeback_sb_inodes+0x96d/0x1680 fs/fs-writeback.c:1733
 wb_writeback+0x40f/0xb80 fs/fs-writeback.c:1908
 wb_do_writeback fs/fs-writeback.c:2053 [inline]
 wb_workfn+0x3ac/0xf30 fs/fs-writeback.c:2094
 process_one_work+0x6fd/0xbc0 kernel/workqueue.c:2301
 worker_thread+0xa8e/0x13c0 kernel/workqueue.c:2447
 kthread+0x324/0x3b0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:298
Modules linked in:
---[ end trace 2c75e22655775129 ]---
RIP: 0010:ext4_ext_insert_extent+0x45b8/0x45f0 fs/ext4/extents.c:2150
Code: ff 44 89 f1 80 e1 07 fe c1 38 c1 0f 8c 01 e9 ff ff 4c 89 f7 e8 09 5c d4 ff e9 f4 e8 ff ff e8 1f e7 99 ff 0f 0b e8 18 e7 99 ff <0f> 0b e8 11 e7 99 ff 0f 0b 89 d9 80 e1 07 80 c1 03 38 c1 0f 8c fe
RSP: 0018:ffffc90000cc6b60 EFLAGS: 00010293
RAX: ffffffff81cabc48 RBX: ffff888122b7f000 RCX: ffff88810c644f00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000cc6d10 R08: ffff88811aa0049f R09: 1ffff11023540093
R10: dffffc0000000000 R11: ffffed1023540094 R12: ffff888122b8fbfc
R13: ffff888119ea0040 R14: 0000000000000000 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8881f7000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f2c2a4154d0 CR3: 000000010cd27000 CR4: 00000000003506b0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400