syz.4.28: attempt to access beyond end of device
loop4: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop4, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_block+0x790/0x970 fs/sysv/balloc.c:113
Read of size 4 at addr ffff88805b3200c8 by task syz.4.28/6077

CPU: 0 UID: 0 PID: 6077 Comm: syz.4.28 Not tainted 6.12.0-rc7-syzkaller-00070-g0a9b9d17f3a7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 sysv_new_block+0x790/0x970 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:135 [inline]
 get_block+0x30a/0x16d0 fs/sysv/itree.c:254
 __block_write_begin_int+0x50c/0x1a70 fs/buffer.c:2121
 block_write_begin+0x8f/0x120 fs/buffer.c:2231
 sysv_write_begin+0x31/0x70 fs/sysv/itree.c:490
 page_symlink+0x2a6/0x4a0 fs/namei.c:5362
 sysv_symlink+0xcf/0x180 fs/sysv/namei.c:86
 vfs_symlink+0x137/0x2e0 fs/namei.c:4615
 do_symlinkat+0x222/0x3a0 fs/namei.c:4641
 __do_sys_symlinkat fs/namei.c:4657 [inline]
 __se_sys_symlinkat fs/namei.c:4654 [inline]
 __x64_sys_symlinkat+0x95/0xb0 fs/namei.c:4654
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe54a37e719
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:00007fe54b121038 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007fe54a535f80 RCX: 00007fe54a37e719
RDX: 0000000020000000 RSI: ffffffffffffff9c RDI: 0000000020000140
RBP: 00007fe54a3f175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe54a535f80 R15: 00007ffdd1e32398
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x263 pfn:0x5b320
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 00fff00000000000 ffffea000178a808 ffffea0001692008 0000000000000000
raw: 0000000000000263 0000000000000005 00000000f0000000 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 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 6048, tgid 6047 (syz.4.26), ts 89055267356, free_ts 89944598938
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1556
 prep_new_page mm/page_alloc.c:1564 [inline]
 get_page_from_freelist+0x363e/0x3790 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4750
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 folio_alloc_mpol_noprof+0x36/0x50 mm/mempolicy.c:2283
 shmem_alloc_folio mm/shmem.c:1771 [inline]
 shmem_alloc_and_add_folio+0x49b/0x13d0 mm/shmem.c:1810
 shmem_get_folio_gfp+0x5a9/0x20a0 mm/shmem.c:2332
 shmem_get_folio mm/shmem.c:2438 [inline]
 shmem_write_begin+0x17e/0x460 mm/shmem.c:3040
 generic_perform_write+0x344/0x6d0 mm/filemap.c:4054
 shmem_file_write_iter+0xf9/0x120 mm/shmem.c:3215
 new_sync_write fs/read_write.c:590 [inline]
 vfs_write+0xaeb/0xd30 fs/read_write.c:683
 ksys_write+0x183/0x2b0 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 5844 tgid 5844 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xf21/0x1a10 mm/page_alloc.c:2704
 folios_put_refs+0x76c/0x860 mm/swap.c:993
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x64c/0x1cf0 mm/shmem.c:1032
 shmem_truncate_range mm/shmem.c:1144 [inline]
 shmem_evict_inode+0x29b/0xa80 mm/shmem.c:1274
 evict+0x4e8/0x9b0 fs/inode.c:725
 __dentry_kill+0x20d/0x630 fs/dcache.c:615
 dput+0x19f/0x2b0 fs/dcache.c:857
 __fput+0x5d2/0x880 fs/file_table.c:439
 task_work_run+0x24f/0x310 kernel/task_work.c:239
 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x168/0x370 kernel/entry/common.c:218
 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88805b31ff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805b320000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88805b320080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88805b320100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88805b320180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================