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BUG: KASAN: use-after-free in sysv_new_block+0x788/0x960 fs/sysv/balloc.c:113
Read of size 4 at addr ffff888071fb30c8 by task syz.4.11/4292

CPU: 1 PID: 4292 Comm: syz.4.11 Not tainted 5.15.178-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 print_address_description+0x63/0x3b0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:434 [inline]
 kasan_report+0x16b/0x1c0 mm/kasan/report.c:451
 sysv_new_block+0x788/0x960 fs/sysv/balloc.c:113
 alloc_branch fs/sysv/itree.c:134 [inline]
 get_block+0x2e7/0x1790 fs/sysv/itree.c:253
 __block_write_begin_int+0x60b/0x1650 fs/buffer.c:2012
 sysv_make_empty+0x8a/0x730 fs/sysv/dir.c:257
 sysv_mkdir+0x7b/0x120 fs/sysv/namei.c:130
 vfs_mkdir+0x3b6/0x590 fs/namei.c:4065
 do_mkdirat+0x260/0x520 fs/namei.c:4090
 __do_sys_mkdir fs/namei.c:4110 [inline]
 __se_sys_mkdir fs/namei.c:4108 [inline]
 __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4108
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f063b885da9
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:00007f06396ad038 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 00007f063ba9f160 RCX: 00007f063b885da9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200003c0
RBP: 00007f063b9072a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000001 R14: 00007f063ba9f160 R15: 00007ffe9f92dd68
 </TASK>

The buggy address belongs to the page:
page:ffffea0001c7ecc0 refcount:0 mapcount:0 mapping:0000000000000000 index:0x1 pfn:0x71fb3
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0001c7ed08 ffffea0001c7ec88 0000000000000000
raw: 0000000000000001 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 0x1100dca(GFP_HIGHUSER_MOVABLE|__GFP_ZERO), pid 4287, ts 71109484693, free_ts 72641607695
 prep_new_page mm/page_alloc.c:2426 [inline]
 get_page_from_freelist+0x3b78/0x3d40 mm/page_alloc.c:4192
 __alloc_pages+0x272/0x700 mm/page_alloc.c:5465
 alloc_pages_vma+0x39a/0x800 mm/mempolicy.c:2146
 wp_page_copy+0x221/0x2070 mm/memory.c:3049
 handle_pte_fault mm/memory.c:4666 [inline]
 __handle_mm_fault mm/memory.c:4783 [inline]
 handle_mm_fault+0x2a3d/0x5960 mm/memory.c:4881
 do_user_addr_fault arch/x86/mm/fault.c:1357 [inline]
 handle_page_fault arch/x86/mm/fault.c:1445 [inline]
 exc_page_fault+0x271/0x700 arch/x86/mm/fault.c:1501
 asm_exc_page_fault+0x22/0x30 arch/x86/include/asm/idtentry.h:606
 __put_user_nocheck_4+0x3/0x11
 ____sys_recvmsg+0x35b/0x530 net/socket.c:2668
 ___sys_recvmsg+0x1ec/0x690 net/socket.c:2697
 do_recvmmsg+0x36f/0x8f0 net/socket.c:2791
 __sys_recvmmsg net/socket.c:2870 [inline]
 __do_sys_recvmmsg net/socket.c:2893 [inline]
 __se_sys_recvmmsg net/socket.c:2886 [inline]
 __x64_sys_recvmmsg+0x195/0x240 net/socket.c:2886
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1340 [inline]
 free_pcp_prepare mm/page_alloc.c:1391 [inline]
 free_unref_page_prepare+0xc34/0xcf0 mm/page_alloc.c:3317
 free_unref_page_list+0x1f7/0x8e0 mm/page_alloc.c:3433
 release_pages+0x1bb9/0x1f40 mm/swap.c:963
 tlb_batch_pages_flush mm/mmu_gather.c:49 [inline]
 tlb_flush_mmu_free mm/mmu_gather.c:240 [inline]
 tlb_flush_mmu+0xc8/0x170 mm/mmu_gather.c:247
 zap_pte_range mm/memory.c:1456 [inline]
 zap_pmd_range mm/memory.c:1505 [inline]
 zap_pud_range mm/memory.c:1534 [inline]
 zap_p4d_range mm/memory.c:1555 [inline]
 unmap_page_range+0x214d/0x2630 mm/memory.c:1576
 unmap_vmas+0x1f8/0x390 mm/memory.c:1653
 exit_mmap+0x3b6/0x620 mm/mmap.c:3204
 __mmput+0x112/0x3b0 kernel/fork.c:1127
 exit_mm+0x688/0x7f0 kernel/exit.c:550
 do_exit+0x626/0x2480 kernel/exit.c:861
 do_group_exit+0x144/0x310 kernel/exit.c:996
 get_signal+0xc66/0x14e0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xc3/0x1890 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x97/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x5d/0x240 kernel/entry/common.c:307

Memory state around the buggy address:
 ffff888071fb2f80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888071fb3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888071fb3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                              ^
 ffff888071fb3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888071fb3180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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