syz.6.286: attempt to access beyond end of device
loop6: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop6, 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 ffff888054a990c8 by task syz.6.286/7466

CPU: 1 UID: 0 PID: 7466 Comm: syz.6.286 Not tainted 6.12.0-syzkaller-08446-g228a1157fb9f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
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+0x50e/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+0x2a8/0x4a0 fs/namei.c:5416
 sysv_symlink+0xcf/0x180 fs/sysv/namei.c:86
 vfs_symlink+0x139/0x2e0 fs/namei.c:4669
 do_symlinkat+0x222/0x3a0 fs/namei.c:4695
 __do_sys_symlink fs/namei.c:4716 [inline]
 __se_sys_symlink fs/namei.c:4714 [inline]
 __x64_sys_symlink+0x7a/0x90 fs/namei.c:4714
 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: 0033:0x7fa58457e819
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:00007fa5843b7038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007fa584736160 RCX: 00007fa58457e819
RDX: 0000000000000000 RSI: 00000000200059c0 RDI: 00000000200049c0
RBP: 00007fa5845f175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007fa584736160 R15: 00007fff01196b18
 </TASK>

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:ffff8880595ad888 index:0x4ee pfn:0x54a99
memcg:ffff888048332000
aops:shmem_aops ino:53 dentry name(?):"memfd:syzkaller"
flags: 0xfff6000002003c(referenced|uptodate|dirty|lru|swapbacked|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff6000002003c ffffea000152a608 ffffea000152a688 ffff8880595ad888
raw: 00000000000004ee 0000000000000000 00000001ffffffff ffff888048332000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Movable, gfp_mask 0x140cca(GFP_HIGHUSER_MOVABLE|__GFP_COMP), pid 7462, tgid 7461 (syz.8.289), ts 182710798676, free_ts 181643913292
 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+0x3649/0x3790 mm/page_alloc.c:3474
 __alloc_pages_noprof+0x292/0x710 mm/page_alloc.c:4751
 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:1774 [inline]
 shmem_alloc_and_add_folio+0x49b/0x13d0 mm/shmem.c:1813
 shmem_get_folio_gfp+0x5a9/0x20a0 mm/shmem.c:2335
 shmem_get_folio mm/shmem.c:2441 [inline]
 shmem_write_begin+0x17e/0x460 mm/shmem.c:3094
 generic_perform_write+0x346/0x6d0 mm/filemap.c:4056
 shmem_file_write_iter+0xf9/0x120 mm/shmem.c:3269
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0xaed/0xd30 fs/read_write.c:679
 ksys_write+0x18f/0x2b0 fs/read_write.c:731
 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 6399 tgid 6399 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xf37/0x1a20 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:1037
 shmem_truncate_range mm/shmem.c:1149 [inline]
 shmem_evict_inode+0x29b/0xa80 mm/shmem.c:1277
 evict+0x4ea/0x9a0 fs/inode.c:796
 __dentry_kill+0x20d/0x630 fs/dcache.c:625
 dput+0x19f/0x2b0 fs/dcache.c:867
 __fput+0x5ba/0xa50 fs/file_table.c:458
 task_work_run+0x251/0x310 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:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x13f/0x340 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:
 ffff888054a98f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888054a99000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888054a99080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
                                              ^
 ffff888054a99100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888054a99180: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================