syz.7.2422: attempt to access beyond end of device
loop7: rw=0, sector=6491536, nr_sectors = 2 limit=128
buffer_io_error: 1 callbacks suppressed
Buffer I/O error on dev loop7, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_block+0x7bf/0xa70 fs/sysv/balloc.c:113
Read of size 4 at addr ffff8880536910c8 by task syz.7.2422/19354

CPU: 1 UID: 0 PID: 19354 Comm: syz.7.2422 Not tainted 6.14.0-rc7-syzkaller-00137-g5fc319360819 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_address_description mm/kasan/report.c:408 [inline]
 print_report+0xc3/0x670 mm/kasan/report.c:521
 kasan_report+0xd9/0x110 mm/kasan/report.c:634
 sysv_new_block+0x7bf/0xa70 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:135 [inline]
 get_block+0x261/0x1570 fs/sysv/itree.c:254
 __block_write_begin_int+0x4fe/0x16e0 fs/buffer.c:2116
 block_write_begin+0x9a/0x1d0 fs/buffer.c:2226
 sysv_write_begin+0x31/0xe0 fs/sysv/itree.c:490
 page_symlink+0x3bc/0x440 fs/namei.c:5436
 sysv_symlink+0xd3/0x180 fs/sysv/namei.c:86
 vfs_symlink fs/namei.c:4671 [inline]
 vfs_symlink+0x3eb/0x660 fs/namei.c:4655
 do_symlinkat+0x263/0x310 fs/namei.c:4697
 __do_sys_symlink fs/namei.c:4718 [inline]
 __se_sys_symlink fs/namei.c:4716 [inline]
 __x64_sys_symlink+0x75/0x90 fs/namei.c:4716
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3b4458d169
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:00007f3b453bf038 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 00007f3b447a6160 RCX: 00007f3b4458d169
RDX: 0000000000000000 RSI: 000020000000acc0 RDI: 000020000000ad80
RBP: 00007f3b4460e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3b447a6160 R15: 00007ffcd62ae318
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x5ce pfn:0x53691
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000000000005ce 0000000000000000 00000000ffffffff 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 19075, tgid 19074 (syz.9.2370), ts 1674131724436, free_ts 1674474762826
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x181/0x1b0 mm/page_alloc.c:1551
 prep_new_page mm/page_alloc.c:1559 [inline]
 get_page_from_freelist+0xfce/0x2f80 mm/page_alloc.c:3477
 __alloc_frozen_pages_noprof+0x221/0x2470 mm/page_alloc.c:4740
 alloc_pages_mpol+0x1fc/0x540 mm/mempolicy.c:2270
 folio_alloc_mpol_noprof+0x36/0x2f0 mm/mempolicy.c:2289
 shmem_alloc_folio+0x135/0x160 mm/shmem.c:1863
 shmem_alloc_and_add_folio+0x48e/0xc10 mm/shmem.c:1902
 shmem_get_folio_gfp+0x689/0x1530 mm/shmem.c:2545
 shmem_fault+0x200/0xae0 mm/shmem.c:2746
 __do_fault+0x10d/0x490 mm/memory.c:4989
 do_read_fault mm/memory.c:5409 [inline]
 do_fault mm/memory.c:5543 [inline]
 do_pte_missing+0xecf/0x3e10 mm/memory.c:4059
 handle_pte_fault mm/memory.c:5888 [inline]
 __handle_mm_fault+0x103c/0x2a40 mm/memory.c:6031
 handle_mm_fault+0x3fa/0xaa0 mm/memory.c:6200
 faultin_page mm/gup.c:1196 [inline]
 __get_user_pages+0x773/0x36f0 mm/gup.c:1491
 populate_vma_page_range+0x27f/0x3a0 mm/gup.c:1929
 __mm_populate+0x1d6/0x380 mm/gup.c:2032
page last free pid 19083 tgid 19074 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1127 [inline]
 free_unref_folios+0xa7b/0x1500 mm/page_alloc.c:2707
 folios_put_refs+0x587/0x7b0 mm/swap.c:994
 folio_batch_release include/linux/pagevec.h:101 [inline]
 shmem_undo_range+0x586/0x1170 mm/shmem.c:1112
 shmem_truncate_range mm/shmem.c:1224 [inline]
 shmem_evict_inode+0x3a3/0xba0 mm/shmem.c:1352
 evict+0x40c/0x960 fs/inode.c:796
 iput_final fs/inode.c:1946 [inline]
 iput fs/inode.c:1972 [inline]
 iput+0x52a/0x890 fs/inode.c:1958
 dentry_unlink_inode+0x29c/0x480 fs/dcache.c:440
 __dentry_kill+0x1d0/0x600 fs/dcache.c:643
 dput.part.0+0x4b1/0x9b0 fs/dcache.c:885
 dput+0x1f/0x30 fs/dcache.c:875
 __fput+0x51c/0xb70 fs/file_table.c:472
 task_work_run+0x151/0x250 kernel/task_work.c:227
 exit_task_work include/linux/task_work.h:40 [inline]
 do_exit+0xad8/0x2db0 kernel/exit.c:938
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1087
 get_signal+0x24ed/0x26c0 kernel/signal.c:3036
 arch_do_signal_or_restart+0x90/0x7e0 arch/x86/kernel/signal.c:337

Memory state around the buggy address:
 ffff888053690f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888053691000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888053691080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888053691100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888053691180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================