syzbot

VFS: Found a Xenix FS (block size = 1024) on device loop0
syz-executor391: attempt to access beyond end of device
loop0: rw=0, sector=6491536, nr_sectors = 2 limit=128
Buffer I/O error on dev loop0, logical block 3245768, async page read
==================================================================
BUG: KASAN: use-after-free in sysv_new_inode+0xfc7/0x1160 fs/sysv/ialloc.c:153
Read of size 2 at addr ffff88807e7bd1ce by task syz-executor391/5846

CPU: 0 UID: 0 PID: 5846 Comm: syz-executor391 Not tainted 6.12.0-syzkaller-10313-g7d4050728c83 #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:378 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:489
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 sysv_new_inode+0xfc7/0x1160 fs/sysv/ialloc.c:153
 sysv_symlink+0x9f/0x180 fs/sysv/namei.c:80
 vfs_symlink+0x137/0x2e0 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: 0033:0x7ffac3182749
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 b1 1c 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff7c2c0ae8 EFLAGS: 00000246 ORIG_RAX: 0000000000000058
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007ffac3182749
RDX: 0000000000000000 RSI: 0000000020000200 RDI: 00000000200049c0
RBP: 0000000000000000 R08: 0000000000009e7f R09: 00007fff7c2c0b1c
R10: 00007fff7c2c09b0 R11: 0000000000000246 R12: 00007fff7c2c0b1c
R13: 0000000000000001 R14: 431bde82d7b634db R15: 00007fff7c2c0b50
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x7f68329e5 pfn:0x7e7bd
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 00000007f68329e5 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 0x140dca(GFP_HIGHUSER_MOVABLE|__GFP_COMP|__GFP_ZERO), pid 5833, tgid 5833 (sshd), ts 55885858589, free_ts 55892796337
 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:4751
 alloc_pages_mpol_noprof+0x3e8/0x680 mm/mempolicy.c:2265
 folio_alloc_mpol_noprof mm/mempolicy.c:2283 [inline]
 vma_alloc_folio_noprof+0x12e/0x230 mm/mempolicy.c:2313
 folio_prealloc+0x2e/0x170
 alloc_anon_folio mm/memory.c:4752 [inline]
 do_anonymous_page mm/memory.c:4809 [inline]
 do_pte_missing mm/memory.c:3977 [inline]
 handle_pte_fault+0x2518/0x68a0 mm/memory.c:5801
 __handle_mm_fault mm/memory.c:5944 [inline]
 handle_mm_fault+0x1053/0x1ad0 mm/memory.c:6112
 do_user_addr_fault arch/x86/mm/fault.c:1338 [inline]
 handle_page_fault arch/x86/mm/fault.c:1481 [inline]
 exc_page_fault+0x459/0x8c0 arch/x86/mm/fault.c:1539
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:623
page last free pid 5833 tgid 5833 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:962
 free_pages_and_swap_cache+0x2ea/0x690 mm/swap_state.c:332
 __tlb_batch_free_encoded_pages mm/mmu_gather.c:136 [inline]
 tlb_batch_pages_flush mm/mmu_gather.c:149 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:366 [inline]
 tlb_flush_mmu+0x3a3/0x680 mm/mmu_gather.c:373
 tlb_finish_mmu+0xd4/0x200 mm/mmu_gather.c:465
 vms_clear_ptes+0x437/0x530 mm/vma.c:1143
 vms_complete_munmap_vmas+0x210/0x8f0 mm/vma.c:1185
 do_vmi_align_munmap+0x5ef/0x6f0 mm/vma.c:1444
 do_vmi_munmap+0x24e/0x2d0 mm/vma.c:1492
 __vm_munmap+0x24c/0x480 mm/mmap.c:1367
 __do_sys_munmap mm/mmap.c:1384 [inline]
 __se_sys_munmap mm/mmap.c:1381 [inline]
 __x64_sys_munmap+0x60/0x70 mm/mmap.c:1381
 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

Memory state around the buggy address:
 ffff88807e7bd080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807e7bd100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88807e7bd180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff88807e7bd200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88807e7bd280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
==================================================================