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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 ffff888128f8cc00 by task syz.0.10/339

CPU: 1 PID: 339 Comm: syz.0.10 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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+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+0x20b/0x5e00 fs/ext4/extents.c:4176
 ext4_map_blocks+0x3b1/0x1bd0 fs/ext4/inode.c:601
 ext4_mpage_readpages+0xa05/0x2110 fs/ext4/readpage.c:343
 ext4_readpage+0x10e/0x220 fs/ext4/inode.c:3339
 filemap_fault+0x1abd/0x20d0 mm/filemap.c:2875
 ext4_filemap_fault+0x8a/0xa0 fs/ext4/inode.c:6412
 __do_fault mm/memory.c:4064 [inline]
 do_read_fault mm/memory.c:4399 [inline]
 do_fault mm/memory.c:4527 [inline]
 handle_pte_fault+0x1fa5/0x3750 mm/memory.c:4791
 __handle_mm_fault mm/memory.c:4944 [inline]
 handle_mm_fault+0xf81/0x1710 mm/memory.c:5358
 faultin_page mm/gup.c:902 [inline]
 __get_user_pages+0xbf8/0x1400 mm/gup.c:1121
 populate_vma_page_range mm/gup.c:1454 [inline]
 __mm_populate+0x34f/0x440 mm/gup.c:1502
 mm_populate include/linux/mm.h:2793 [inline]
 vm_mmap_pgoff+0x254/0x370 mm/util.c:548
 ksys_mmap_pgoff+0x16f/0x1e0 mm/mmap.c:1712
 __do_sys_mmap arch/x86/kernel/sys_x86_64.c:95 [inline]
 __se_sys_mmap arch/x86/kernel/sys_x86_64.c:86 [inline]
 __x64_sys_mmap+0xfa/0x110 arch/x86/kernel/sys_x86_64.c:86
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f10eebdbdd9
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:00007f10ed636028 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: ffffffffffffffda RBX: 00007f10eee54fa0 RCX: 00007f10eebdbdd9
RDX: 000000000100000a RSI: 0000000000b36000 RDI: 0000200000000000
RBP: 00007f10eec71d69 R08: 0000000000000004 R09: 0000000000000000
R10: 0000000000028011 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f10eee55038 R14: 00007f10eee54fa0 R15: 00007fff828bf7f8

Allocated by task 339:
 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:2952 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 kmem_cache_alloc+0x162/0x2d0 mm/slub.c:2965
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x11e/0x460 mm/mempool.c:393
 bio_alloc_bioset+0x18c/0x570 block/bio.c:486
 bio_alloc include/linux/bio.h:412 [inline]
 submit_bh_wbc+0x1c6/0x6f0 fs/buffer.c:3057
 submit_bh fs/buffer.c:3091 [inline]
 __sync_dirty_buffer+0x214/0x320 fs/buffer.c:3186
 sync_dirty_buffer+0x1a/0x20 fs/buffer.c:3199
 __ext4_handle_dirty_metadata+0x282/0x7f0 fs/ext4/ext4_jbd2.c:366
 __ext4_ext_dirty+0xfb/0x1e0 fs/ext4/extents.c:175
 ext4_ext_insert_extent+0x2aa5/0x45d0 fs/ext4/extents.c:2175
 ext4_ext_map_blocks+0x1709/0x5e00 fs/ext4/extents.c:4372
 ext4_map_blocks+0x985/0x1bd0 fs/ext4/inode.c:674
 _ext4_get_block+0x1d1/0x4e0 fs/ext4/inode.c:817
 ext4_get_block_unwritten+0x2a/0x40 fs/ext4/inode.c:848
 ext4_block_write_begin+0x573/0x1340 fs/ext4/inode.c:1101
 ext4_write_begin+0x67e/0x1690 fs/ext4/ext4_jbd2.h:-1
 ext4_da_write_begin+0x478/0xf10 fs/ext4/inode.c:3033
 generic_perform_write+0x2ce/0x540 mm/filemap.c:3509
 ext4_buffered_write_iter+0x4b8/0x640 fs/ext4/file.c:271
 ext4_file_write_iter+0x53f/0x1980 fs/ext4/file.c:-1
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x758/0xdc0 fs/read_write.c:605
 ksys_write+0x149/0x250 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

Freed by task 12:
 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]
 kmem_cache_free+0x100/0x2d0 mm/slub.c:3224
 mempool_free_slab+0x1d/0x30 mm/mempool.c:520
 mempool_free+0xd8/0x340 mm/mempool.c:502
 bio_free+0x24a/0x360 block/bio.c:266
 bio_put+0xbf/0x110 block/bio.c:-1
 end_bio_bh_io_sync+0xc4/0x120 fs/buffer.c:3037
 bio_endio+0x646/0x860 block/bio.c:1458
 req_bio_endio block/blk-core.c:263 [inline]
 blk_update_request+0x74a/0x1090 block/blk-core.c:1468
 blk_mq_end_request+0x41/0x80 block/blk-mq.c:572
 lo_complete_rq+0x147/0x2d0 drivers/block/loop.c:490
 blk_done_softirq+0x26f/0x2f0 block/blk-mq.c:596
 __do_softirq+0x255/0x563 kernel/softirq.c:309

The buggy address belongs to the object at ffff888128f8cb40
 which belongs to the cache bio-0 of size 216
The buggy address is located 192 bytes inside of
 216-byte region [ffff888128f8cb40, ffff888128f8cc18)
The buggy address belongs to the page:
page:ffffea0004a3e300 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x128f8c
flags: 0x4000000000000200(slab)
raw: 4000000000000200 dead000000000100 dead000000000122 ffff888107fbe900
raw: 0000000000000000 00000000000c000c 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x192800(GFP_NOWAIT|__GFP_NOWARN|__GFP_NORETRY|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 339, ts 24826719465, 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+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x223b/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x290/0x620 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+0x2a6/0x450 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+0x1ac/0x2d0 mm/slub.c:2965
 mempool_alloc_slab+0x1d/0x30 mm/mempool.c:513
 mempool_alloc+0x11e/0x460 mm/mempool.c:393
 bio_alloc_bioset+0x18c/0x570 block/bio.c:486
 bio_alloc include/linux/bio.h:412 [inline]
 submit_bh_wbc+0x1c6/0x6f0 fs/buffer.c:3057
 submit_bh fs/buffer.c:3091 [inline]
 __sync_dirty_buffer+0x214/0x320 fs/buffer.c:3186
 sync_dirty_buffer+0x1a/0x20 fs/buffer.c:3199
 __ext4_handle_dirty_metadata+0x282/0x7f0 fs/ext4/ext4_jbd2.c:366
 __ext4_ext_dirty+0xfb/0x1e0 fs/ext4/extents.c:175
 ext4_ext_insert_extent+0x2aa5/0x45d0 fs/ext4/extents.c:2175
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888128f8cb00: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
 ffff888128f8cb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888128f8cc00: fb fb fb fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff888128f8cc80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888128f8cd00: fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc fc
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