linux-kernel - Re: [syzbot] kernel BUG in __page

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Message-ID: <0000000000009411bb05d3ab468f@google.com>
Date:   Tue, 21 Dec 2021 09:24:20 -0800
From:   syzbot <syzbot+1f52b3a18d5633fa7f82@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, apopple@...dia.com,
        chinwen.chang@...iatek.com, fgheet255t@...il.com, jannh@...gle.com,
        khlebnikov@...dex-team.ru, kirill.shutemov@...ux.intel.com,
        kirill@...temov.name, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        peterx@...hat.com, peterz@...radead.org,
        syzkaller-bugs@...glegroups.com, tonymarislogistics@...dex.com,
        vbabka@...e.cz, walken@...gle.com, willy@...radead.org,
        ziy@...dia.com
Subject: Re: [syzbot] kernel BUG in __page_mapcount

syzbot has found a reproducer for the following issue on:

HEAD commit:    6e0567b73052 Merge tag 'for-linus' of git://git.kernel.org..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14c192b3b00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ae22d1ee4fbca18
dashboard link: https://syzkaller.appspot.com/bug?extid=1f52b3a18d5633fa7f82
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=133200fdb00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17c3102db00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1f52b3a18d5633fa7f82@...kaller.appspotmail.com

 __mmput+0x122/0x4b0 kernel/fork.c:1113
 mmput+0x56/0x60 kernel/fork.c:1134
 exit_mm kernel/exit.c:507 [inline]
 do_exit+0xb27/0x2b40 kernel/exit.c:819
 do_group_exit+0x125/0x310 kernel/exit.c:929
 get_signal+0x47d/0x2220 kernel/signal.c:2852
 arch_do_signal_or_restart+0x2a9/0x1c40 arch/x86/kernel/signal.c:868
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x17d/0x290 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x19/0x60 kernel/entry/common.c:300
 do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae
------------[ cut here ]------------
kernel BUG at include/linux/page-flags.h:785!
invalid opcode: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 4392 Comm: syz-executor560 Not tainted 5.16.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:PageDoubleMap include/linux/page-flags.h:785 [inline]
RIP: 0010:__page_mapcount+0x2d2/0x350 mm/util.c:744
Code: e8 d3 16 d1 ff 48 c7 c6 c0 00 b6 89 48 89 ef e8 94 4e 04 00 0f 0b e8 bd 16 d1 ff 48 c7 c6 60 01 b6 89 48 89 ef e8 7e 4e 04 00 <0f> 0b e8 a7 16 d1 ff 48 c7 c6 a0 01 b6 89 4c 89 f7 e8 68 4e 04 00
RSP: 0018:ffffc90002b6f7b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888019619d00 RSI: ffffffff81a68c12 RDI: 0000000000000003
RBP: ffffea0001bdc2c0 R08: 0000000000000029 R09: 00000000ffffffff
R10: ffffffff8903e29f R11: 00000000ffffffff R12: 00000000ffffffff
R13: 00000000ffffea00 R14: ffffc90002b6fb30 R15: ffffea0001bd8001
FS:  00007faa2aefd700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff7e663318 CR3: 0000000018c6e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 page_mapcount include/linux/mm.h:837 [inline]
 smaps_account+0x470/0xb10 fs/proc/task_mmu.c:466
 smaps_pte_entry fs/proc/task_mmu.c:538 [inline]
 smaps_pte_range+0x611/0x1250 fs/proc/task_mmu.c:601
 walk_pmd_range mm/pagewalk.c:128 [inline]
 walk_pud_range mm/pagewalk.c:205 [inline]
 walk_p4d_range mm/pagewalk.c:240 [inline]
 walk_pgd_range mm/pagewalk.c:277 [inline]
 __walk_page_range+0xe23/0x1ea0 mm/pagewalk.c:379
 walk_page_vma+0x277/0x350 mm/pagewalk.c:530
 smap_gather_stats.part.0+0x148/0x260 fs/proc/task_mmu.c:768
 smap_gather_stats fs/proc/task_mmu.c:741 [inline]
 show_smap+0xc6/0x440 fs/proc/task_mmu.c:822
 seq_read_iter+0xbb0/0x1240 fs/seq_file.c:272
 seq_read+0x3e0/0x5b0 fs/seq_file.c:162
 vfs_read+0x1b5/0x600 fs/read_write.c:479
 ksys_read+0x12d/0x250 fs/read_write.c:619
 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+0x44/0xae
RIP: 0033:0x7faa2af6c969
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:00007faa2aefd288 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007faa2aff4418 RCX: 00007faa2af6c969
RDX: 0000000000002025 RSI: 0000000020000100 RDI: 0000000000000003
RBP: 00007faa2aff4410 R08: 00007faa2aefd700 R09: 0000000000000000
R10: 00007faa2aefd700 R11: 0000000000000246 R12: 00007faa2afc20ac
R13: 00007fff7e6632bf R14: 00007faa2aefd400 R15: 0000000000022000
 </TASK>
Modules linked in:
---[ end trace 24ec93ff95e4ac3d ]---
RIP: 0010:PageDoubleMap include/linux/page-flags.h:785 [inline]
RIP: 0010:__page_mapcount+0x2d2/0x350 mm/util.c:744
Code: e8 d3 16 d1 ff 48 c7 c6 c0 00 b6 89 48 89 ef e8 94 4e 04 00 0f 0b e8 bd 16 d1 ff 48 c7 c6 60 01 b6 89 48 89 ef e8 7e 4e 04 00 <0f> 0b e8 a7 16 d1 ff 48 c7 c6 a0 01 b6 89 4c 89 f7 e8 68 4e 04 00
RSP: 0018:ffffc90002b6f7b8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888019619d00 RSI: ffffffff81a68c12 RDI: 0000000000000003
RBP: ffffea0001bdc2c0 R08: 0000000000000029 R09: 00000000ffffffff
R10: ffffffff8903e29f R11: 00000000ffffffff R12: 00000000ffffffff
R13: 00000000ffffea00 R14: ffffc90002b6fb30 R15: ffffea0001bd8001
FS:  00007faa2aefd700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fff7e663318 CR3: 0000000018c6e000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400