Message-ID: <0000000000009b692105e153af25@google.com>
Date:   Mon, 13 Jun 2022 05:47:08 -0700
From:   syzbot <syzbot+68771c0e74f7bb7804e5@...kaller.appspotmail.com>
To:     hdanton@...a.com, linux-kernel@...r.kernel.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] KASAN: use-after-free Read in __vma_adjust

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KASAN: use-after-free Write in userfaultfd_release

==================================================================
BUG: KASAN: use-after-free in userfaultfd_release+0x651/0x670 fs/userfaultfd.c:897
Write of size 8 at addr ffff8880781dfe78 by task syz-executor.0/4090

CPU: 0 PID: 4090 Comm: syz-executor.0 Not tainted 5.19.0-rc1-next-20220610-syzkaller-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 print_address_description.constprop.0.cold+0xeb/0x495 mm/kasan/report.c:313
 print_report mm/kasan/report.c:429 [inline]
 kasan_report.cold+0xf4/0x1c6 mm/kasan/report.c:491
 userfaultfd_release+0x651/0x670 fs/userfaultfd.c:897
 __fput+0x277/0x9d0 fs/file_table.c:317
 task_work_run+0xdd/0x1a0 kernel/task_work.c:177
 get_signal+0x1c5/0x2600 kernel/signal.c:2634
 arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
 exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
 exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
RIP: 0033:0x7f734c489109
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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f734d629168 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: fffffffffffffe00 RBX: 00007f734c59bf60 RCX: 00007f734c489109
RDX: 000000000000003c RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00007f734d6291d0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffcee01460f R14: 00007f734d629300 R15: 0000000000022000
 </TASK>

Allocated by task 4069:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track mm/kasan/common.c:45 [inline]
 set_alloc_info mm/kasan/common.c:436 [inline]
 __kasan_slab_alloc+0x90/0xc0 mm/kasan/common.c:469
 kasan_slab_alloc include/linux/kasan.h:224 [inline]
 slab_post_alloc_hook mm/slab.h:750 [inline]
 slab_alloc_node mm/slub.c:3214 [inline]
 slab_alloc mm/slub.c:3222 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
 kmem_cache_alloc+0x204/0x3b0 mm/slub.c:3239
 vm_area_dup+0x81/0x380 kernel/fork.c:466
 dup_mmap+0x656/0x1090 kernel/fork.c:640
 dup_mm+0x91/0x370 kernel/fork.c:1520
 copy_mm kernel/fork.c:1569 [inline]
 copy_process+0x3c95/0x7080 kernel/fork.c:2234
 kernel_clone+0xe7/0xab0 kernel/fork.c:2649
 __do_sys_clone+0xba/0x100 kernel/fork.c:2783
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Freed by task 4090:
 kasan_save_stack+0x1e/0x40 mm/kasan/common.c:38
 kasan_set_track+0x21/0x30 mm/kasan/common.c:45
 kasan_set_free_info+0x20/0x30 mm/kasan/generic.c:370
 ____kasan_slab_free mm/kasan/common.c:366 [inline]
 ____kasan_slab_free+0x166/0x1a0 mm/kasan/common.c:328
 kasan_slab_free include/linux/kasan.h:200 [inline]
 slab_free_hook mm/slub.c:1727 [inline]
 slab_free_freelist_hook+0x8b/0x1c0 mm/slub.c:1753
 slab_free mm/slub.c:3507 [inline]
 kmem_cache_free+0xdd/0x5a0 mm/slub.c:3524
 __vma_adjust+0x9ae/0x1910 mm/mmap.c:889
 vma_merge+0x590/0x870 mm/mmap.c:1123
 userfaultfd_release+0x4c5/0x670 fs/userfaultfd.c:888
 __fput+0x277/0x9d0 fs/file_table.c:317
 task_work_run+0xdd/0x1a0 kernel/task_work.c:177
 get_signal+0x1c5/0x2600 kernel/signal.c:2634
 arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869
 exit_to_user_mode_loop kernel/entry/common.c:166 [inline]
 exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:294
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

The buggy address belongs to the object at ffff8880781dfe58
 which belongs to the cache vm_area_struct of size 152
The buggy address is located 32 bytes inside of
 152-byte region [ffff8880781dfe58, ffff8880781dfef0)

The buggy address belongs to the physical page:
page:ffffea0001e077c0 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x781df
memcg:ffff88801e8b2f01
flags: 0xfff00000000200(slab|node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000200 ffffea0000973500 dead000000000007 ffff888140006b40
raw: 0000000000000000 0000000000120012 00000001ffffffff ffff88801e8b2f01
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x112cc0(GFP_USER|__GFP_NOWARN|__GFP_NORETRY), pid 3812, tgid 3812 (sed), ts 62101588097, free_ts 62100288733
 prep_new_page mm/page_alloc.c:2460 [inline]
 get_page_from_freelist+0xa64/0x3d10 mm/page_alloc.c:4279
 __alloc_pages+0x1c7/0x510 mm/page_alloc.c:5500
 alloc_pages+0x1aa/0x310 mm/mempolicy.c:2279
 alloc_slab_page mm/slub.c:1797 [inline]
 allocate_slab+0x26c/0x3c0 mm/slub.c:1942
 new_slab mm/slub.c:2002 [inline]
 ___slab_alloc+0x985/0xd90 mm/slub.c:3002
 __slab_alloc.constprop.0+0x4d/0xa0 mm/slub.c:3089
 slab_alloc_node mm/slub.c:3180 [inline]
 slab_alloc mm/slub.c:3222 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3229 [inline]
 kmem_cache_alloc+0x360/0x3b0 mm/slub.c:3239
 vm_area_alloc+0x1c/0xf0 kernel/fork.c:458
 __install_special_mapping+0x2e/0x3a0 mm/mmap.c:3489
 map_vdso+0x131/0x390 arch/x86/entry/vdso/vma.c:268
 load_elf_binary+0x206e/0x4ec0 fs/binfmt_elf.c:1287
 search_binary_handler fs/exec.c:1728 [inline]
 exec_binprm fs/exec.c:1769 [inline]
 bprm_execve fs/exec.c:1838 [inline]
 bprm_execve+0x7ef/0x1970 fs/exec.c:1800
 do_execveat_common+0x724/0x890 fs/exec.c:1943
 do_execve fs/exec.c:2017 [inline]
 __do_sys_execve fs/exec.c:2093 [inline]
 __se_sys_execve fs/exec.c:2088 [inline]
 __x64_sys_execve+0x8f/0xc0 fs/exec.c:2088
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1375 [inline]
 free_pcp_prepare+0x549/0xd20 mm/page_alloc.c:1425
 free_unref_page_prepare mm/page_alloc.c:3311 [inline]
 free_unref_page_list+0x184/0x1530 mm/page_alloc.c:3475
 release_pages+0xff1/0x2290 mm/swap.c:980
 tlb_batch_pages_flush+0xa8/0x1a0 mm/mmu_gather.c:58
 tlb_flush_mmu_free mm/mmu_gather.c:255 [inline]
 tlb_flush_mmu mm/mmu_gather.c:262 [inline]
 tlb_finish_mmu+0x147/0x7e0 mm/mmu_gather.c:353
 exit_mmap+0x217/0x750 mm/mmap.c:3209
 __mmput+0x128/0x4c0 kernel/fork.c:1180
 mmput+0x5c/0x70 kernel/fork.c:1201
 exec_mmap fs/exec.c:1038 [inline]
 begin_new_exec+0xfbd/0x2e50 fs/exec.c:1297
 load_elf_binary+0x15a3/0x4ec0 fs/binfmt_elf.c:1002
 search_binary_handler fs/exec.c:1728 [inline]
 exec_binprm fs/exec.c:1769 [inline]
 bprm_execve fs/exec.c:1838 [inline]
 bprm_execve+0x7ef/0x1970 fs/exec.c:1800
 do_execveat_common+0x724/0x890 fs/exec.c:1943
 do_execve fs/exec.c:2017 [inline]
 __do_sys_execve fs/exec.c:2093 [inline]
 __se_sys_execve fs/exec.c:2088 [inline]
 __x64_sys_execve+0x8f/0xc0 fs/exec.c:2088
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Memory state around the buggy address:
 ffff8880781dfd00: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
 ffff8880781dfd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880781dfe00: 00 00 00 fc fc fc fc fc fc fc fc fa fb fb fb fb
                                                                ^
 ffff8880781dfe80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff8880781dff00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================


Tested on:

commit:         6d0c8068 Add linux-next specific files for 20220610
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
console output: https://syzkaller.appspot.com/x/log.txt?x=13e7c01bf00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a30d6e3e814e5931
dashboard link: https://syzkaller.appspot.com/bug?extid=68771c0e74f7bb7804e5
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=1679062ff00000

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