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BUG: KASAN: slab-out-of-bounds in ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
BUG: KASAN: slab-out-of-bounds in ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:956
Read of size 4 at addr ffff8880256d4400 by task syz.1.17/6614

CPU: 1 UID: 0 PID: 6614 Comm: syz.1.17 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:378 [inline]
 print_report+0xca/0x240 mm/kasan/report.c:482
 kasan_report+0x118/0x150 mm/kasan/report.c:595
 ext4_ext_binsearch fs/ext4/extents.c:841 [inline]
 ext4_find_extent+0xae6/0xcc0 fs/ext4/extents.c:956
 ext4_ext_map_blocks+0x278/0x6ab0 fs/ext4/extents.c:4208
 ext4_map_query_blocks+0x135/0x9f0 fs/ext4/inode.c:549
 ext4_map_blocks+0x4c3/0x17e0 fs/ext4/inode.c:778
 _ext4_get_block+0x1fa/0x4c0 fs/ext4/inode.c:915
 ext4_get_block_unwritten+0x2e/0x100 fs/ext4/inode.c:948
 ext4_block_write_begin+0x993/0x1710 fs/ext4/inode.c:1203
 ext4_write_begin+0xb3a/0x1880 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x352/0xd50 fs/ext4/inode.c:3133
 generic_perform_write+0x2c5/0x900 mm/filemap.c:4314
 ext4_buffered_write_iter+0xce/0x3a0 fs/ext4/file.c:299
 ext4_file_write_iter+0x292/0x1bc0 fs/ext4/file.c:-1
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5c9/0xb30 fs/read_write.c:686
 ksys_pwrite64 fs/read_write.c:793 [inline]
 __do_sys_pwrite64 fs/read_write.c:801 [inline]
 __se_sys_pwrite64 fs/read_write.c:798 [inline]
 __x64_sys_pwrite64+0x193/0x220 fs/read_write.c:798
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f9d7ed8e929
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9d7fbbc038 EFLAGS: 00000246 ORIG_RAX: 0000000000000012
RAX: ffffffffffffffda RBX: 00007f9d7efb5fa0 RCX: 00007f9d7ed8e929
RDX: 000000000000fdef RSI: 0000200000000140 RDI: 0000000000000004
RBP: 00007f9d7ee10b39 R08: 0000000000000000 R09: 0000000000000000
R10: 000000000000fecc R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f9d7efb5fa0 R15: 00007fffa3d460c8
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:56 [inline]
 kasan_save_track+0x3e/0x80 mm/kasan/common.c:77
 poison_kmalloc_redzone mm/kasan/common.c:397 [inline]
 __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:414
 kasan_kmalloc include/linux/kasan.h:262 [inline]
 __do_kmalloc_node mm/slub.c:5652 [inline]
 __kvmalloc_node_noprof+0x5d9/0x910 mm/slub.c:7129
 sbitmap_init_node+0x2cd/0x640 lib/sbitmap.c:132
 sbitmap_queue_init_node+0x3e/0x4d0 lib/sbitmap.c:454
 bt_alloc block/blk-mq-tag.c:546 [inline]
 blk_mq_init_tags+0x15c/0x2d0 block/blk-mq-tag.c:571
 blk_mq_alloc_rq_map block/blk-mq.c:3545 [inline]
 blk_mq_alloc_map_and_rqs+0xbb/0x9c0 block/blk-mq.c:4108
 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4130 [inline]
 __blk_mq_alloc_rq_maps block/blk-mq.c:4657 [inline]
 blk_mq_alloc_set_map_and_rqs+0x1a2/0x810 block/blk-mq.c:4688
 blk_mq_alloc_tag_set+0x89d/0xfc0 block/blk-mq.c:4865
 loop_add+0x3c9/0xad0 drivers/block/loop.c:2202
 loop_init+0xd9/0x170 drivers/block/loop.c:2441
 do_one_initcall+0x1fb/0x870 init/main.c:1378
 do_initcall_level+0x104/0x190 init/main.c:1440
 do_initcalls+0x59/0xa0 init/main.c:1456
 kernel_init_freeable+0x334/0x4b0 init/main.c:1688
 kernel_init+0x1d/0x1d0 init/main.c:1578
 ret_from_fork+0x599/0xb30 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

The buggy address belongs to the object at ffff8880256d4000
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 256 bytes to the right of
 allocated 768-byte region [ffff8880256d4000, ffff8880256d4300)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x256d0
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe26dc0 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe26dc0 dead000000000122 0000000000000000
head: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
head: 00fff00000000003 ffffea000095b401 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0x252800(GFP_NOWAIT|__GFP_NORETRY|__GFP_COMP|__GFP_THISNODE), pid 1, tgid 1 (swapper/0), ts 7377195129, free_ts 0
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x234/0x290 mm/page_alloc.c:1846
 prep_new_page mm/page_alloc.c:1854 [inline]
 get_page_from_freelist+0x2365/0x2440 mm/page_alloc.c:3915
 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210
 alloc_slab_page mm/slub.c:3077 [inline]
 allocate_slab+0x7a/0x3b0 mm/slub.c:3248
 new_slab mm/slub.c:3302 [inline]
 ___slab_alloc+0xf56/0x1990 mm/slub.c:4651
 __slab_alloc+0x65/0x100 mm/slub.c:4774
 __slab_alloc_node mm/slub.c:4850 [inline]
 slab_alloc_node mm/slub.c:5246 [inline]
 __do_kmalloc_node mm/slub.c:5651 [inline]
 __kvmalloc_node_noprof+0x6ba/0x910 mm/slub.c:7129
 sbitmap_init_node+0x2cd/0x640 lib/sbitmap.c:132
 sbitmap_queue_init_node+0x3e/0x4d0 lib/sbitmap.c:454
 bt_alloc block/blk-mq-tag.c:546 [inline]
 blk_mq_init_tags+0x15c/0x2d0 block/blk-mq-tag.c:571
 blk_mq_alloc_rq_map block/blk-mq.c:3545 [inline]
 blk_mq_alloc_map_and_rqs+0xbb/0x9c0 block/blk-mq.c:4108
 __blk_mq_alloc_map_and_rqs block/blk-mq.c:4130 [inline]
 __blk_mq_alloc_rq_maps block/blk-mq.c:4657 [inline]
 blk_mq_alloc_set_map_and_rqs+0x1a2/0x810 block/blk-mq.c:4688
 blk_mq_alloc_tag_set+0x89d/0xfc0 block/blk-mq.c:4865
 loop_add+0x3c9/0xad0 drivers/block/loop.c:2202
 loop_init+0xd9/0x170 drivers/block/loop.c:2441
 do_one_initcall+0x1fb/0x870 init/main.c:1378
page_owner free stack trace missing

Memory state around the buggy address:
 ffff8880256d4300: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880256d4380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8880256d4400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff8880256d4480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8880256d4500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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