Message-Id: <20230308122457.c5620872df8e70c7f0621417@linux-foundation.org>
Date:   Wed, 8 Mar 2023 12:24:57 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     syzbot <syzbot+8d95422d3537159ca390@...kaller.appspotmail.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        syzkaller-bugs@...glegroups.com,
        Liam Howlett <liam.howlett@...cle.com>
Subject: Re: [syzbot] [mm?] kernel BUG in find_mergeable_anon_vma

(cc Liam)

On Wed, 08 Mar 2023 05:40:42 -0800 syzbot <syzbot+8d95422d3537159ca390@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    0988a0ea7919 Merge tag 'for-v6.3-part2' of git://git.kerne..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=13fc4754c80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=cab35c936731a347
> dashboard link: https://syzkaller.appspot.com/bug?extid=8d95422d3537159ca390
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=130602bcc80000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10b61b54c80000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/e2d28852dbc0/disk-0988a0ea.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/9ad7e6fa3a8d/vmlinux-0988a0ea.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/7430e1576859/bzImage-0988a0ea.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+8d95422d3537159ca390@...kaller.appspotmail.com
> 
> pgoff 20000 file 0000000000000000 private_data 0000000000000000
> flags: 0x8102172(write|mayread|maywrite|mayexec|growsdown|locked|account|softdirty)
> ------------[ cut here ]------------
> kernel BUG at mm/mmap.c:1108!

Thanks.  That's VM_BUG_ON_VMA(prev != vma, vma);

> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 24456 Comm: syz-executor216 Not tainted 6.2.0-syzkaller-13467-g0988a0ea7919 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
> RIP: 0010:find_mergeable_anon_vma+0x6f0/0x840 mm/mmap.c:1108
> Code: df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 6b 48 3b 6b 50 0f 85 08 fb ff ff e9 06 fb ff ff e8 58 ad bf ff 48 89 ef e8 70 a5 fa ff <0f> 0b 4c 89 f7 e8 06 29 11 00 e9 d2 f9 ff ff e8 fc 28 11 00 e9 a0
> RSP: 0018:ffffc9000b61f888 EFLAGS: 00010286
> RAX: 0000000000000130 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff816931bc RDI: 0000000000000005
> RBP: ffff8880783f97e0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000080000000 R11: 0000000000000000 R12: ffffc9000b61f8b0
> R13: 1ffff920016c3f12 R14: ffff8880783f97e8 R15: fff0000000000fff
> FS:  00007fe0f1f58700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffc5b9a8960 CR3: 000000002bd88000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  __anon_vma_prepare+0x7d/0x580 mm/rmap.c:199
>  anon_vma_prepare include/linux/rmap.h:159 [inline]
>  do_anonymous_page mm/memory.c:4050 [inline]
>  handle_pte_fault mm/memory.c:4907 [inline]
>  __handle_mm_fault+0x3a8f/0x3e60 mm/memory.c:5051
>  handle_mm_fault+0x2ba/0x9c0 mm/memory.c:5197
>  faultin_page mm/gup.c:925 [inline]
>  __get_user_pages+0x4da/0xf30 mm/gup.c:1147
>  populate_vma_page_range+0x2df/0x420 mm/gup.c:1543
>  __mm_populate+0x105/0x3b0 mm/gup.c:1652
>  mm_populate include/linux/mm.h:3026 [inline]
>  vm_mmap_pgoff+0x201/0x280 mm/util.c:547
>  ksys_mmap_pgoff+0x7d/0x5a0 mm/mmap.c:1410
>  do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>  do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80
>  entry_SYSCALL_64_after_hwframe+0x63/0xcd
> RIP: 0033:0x7fe0f1fa6959
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 11 15 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:00007fe0f1f582f8 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
> RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 00007fe0f1fa6959
> RDX: 0000000000000002 RSI: 0000000000001000 RDI: 0000000020002000
> RBP: 00007fe0f202e3e8 R08: 00000000ffffffff R09: 0000000000000000
> R10: 840000000000a132 R11: 0000000000000246 R12: 840000000000a132
> R13: 00007fe0f202e3e0 R14: 00007fe0f202e3ec R15: 0000000000022000
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:find_mergeable_anon_vma+0x6f0/0x840 mm/mmap.c:1108
> Code: df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 6b 48 3b 6b 50 0f 85 08 fb ff ff e9 06 fb ff ff e8 58 ad bf ff 48 89 ef e8 70 a5 fa ff <0f> 0b 4c 89 f7 e8 06 29 11 00 e9 d2 f9 ff ff e8 fc 28 11 00 e9 a0
> RSP: 0018:ffffc9000b61f888 EFLAGS: 00010286
> RAX: 0000000000000130 RBX: 0000000000000000 RCX: 0000000000000000
> RDX: 0000000000000000 RSI: ffffffff816931bc RDI: 0000000000000005
> RBP: ffff8880783f97e0 R08: 0000000000000005 R09: 0000000000000000
> R10: 0000000080000000 R11: 0000000000000000 R12: ffffc9000b61f8b0
> R13: 1ffff920016c3f12 R14: ffff8880783f97e8 R15: fff0000000000fff
> FS:  00007fe0f1f58700(0000) GS:ffff8880b9900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007fe0f1ffc01d CR3: 000000002bd88000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
> 
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this issue, for details see:
> https://goo.gl/tpsmEJ#testing-patches

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