Re: [syzbot] kernel BUG in hugepage_add_anon_rmap

[Hugh Dickins]

On Tue, 1 Mar 2022, syzbot wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    196d330d7fb1 Add linux-next specific files for 20220222
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15b0618a700000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=45b71d0aea81d553
> dashboard link: https://syzkaller.appspot.com/bug?extid=d7ed29a6231d3747fb31
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d7ed29a6231d3747fb31@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> kernel BUG at mm/rmap.c:2330!
> invalid opcode: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 4289 Comm: syz-executor.0 Not tainted 5.17.0-rc5-next-20220222-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> RIP: 0010:hugepage_add_anon_rmap+0x1f5/0x240 mm/rmap.c:2330

Already fixed in next-20220301 by latest version (16f06327291e)
of "mm/migrate: Convert remove_migration_ptes() to folios".

> Code: 89 ef e8 6e ad f8 ff 0f 0b e8 77 b2 c4 ff 48 83 eb 01 e9 a6 fe ff ff e8 69 b2 c4 ff 48 83 eb 01 e9 ff fe ff ff e8 5b b2 c4 ff <0f> 0b e8 54 b2 c4 ff 0f 0b e8 4d b2 c4 ff 49 8d 6c 24 ff eb b4 48
> RSP: 0018:ffffc9000fa8f9b8 EFLAGS: 00010216
> RAX: 0000000000002b78 RBX: 0000000000000000 RCX: ffffc90003bd1000
> RDX: 0000000000040000 RSI: ffffffff81b47f75 RDI: 0000000000000003
> RBP: ffffea0001008040 R08: 0000000000000000 R09: 0000000000000000
> R10: ffffffff81b47eab R11: 0000000000000000 R12: ffff88801e231210
> R13: 0000000020400000 R14: ffff8880738f8700 R15: 0000000000000000
> FS:  00007f1a19594700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f33cc0df300 CR3: 000000001ca70000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  remove_migration_pte+0x5fd/0xc50 mm/migrate.c:234
>  rmap_walk_anon+0x44b/0x9e0 mm/rmap.c:2236
>  rmap_walk+0x92/0xd0 mm/rmap.c:2302
>  remove_migration_ptes mm/migrate.c:271 [inline]
>  unmap_and_move_huge_page mm/migrate.c:1259 [inline]
>  migrate_pages+0x1709/0x4030 mm/migrate.c:1379
>  do_mbind mm/mempolicy.c:1334 [inline]
>  kernel_mbind+0x4d7/0x7d0 mm/mempolicy.c:1481
>  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: 0033:0x7f1a18489059
> 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:00007f1a19594168 EFLAGS: 00000246 ORIG_RAX: 00000000000000ed
> RAX: ffffffffffffffda RBX: 00007f1a1859c030 RCX: 00007f1a18489059
> RDX: 0000000000000000 RSI: 0000000000800000 RDI: 0000000020001000
> RBP: 00007f1a184e308d R08: 0000000000000000 R09: 0000000000000002
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffe5da8cc9f R14: 00007f1a19594300 R15: 0000000000022000
>  </TASK>
> Modules linked in:
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:hugepage_add_anon_rmap+0x1f5/0x240 mm/rmap.c:2330
> Code: 89 ef e8 6e ad f8 ff 0f 0b e8 77 b2 c4 ff 48 83 eb 01 e9 a6 fe ff ff e8 69 b2 c4 ff 48 83 eb 01 e9 ff fe ff ff e8 5b b2 c4 ff <0f> 0b e8 54 b2 c4 ff 0f 0b e8 4d b2 c4 ff 49 8d 6c 24 ff eb b4 48
> RSP: 0018:ffffc9000fa8f9b8 EFLAGS: 00010216
> RAX: 0000000000002b78 RBX: 0000000000000000 RCX: ffffc90003bd1000
> RDX: 0000000000040000 RSI: ffffffff81b47f75 RDI: 0000000000000003
> RBP: ffffea0001008040 R08: 0000000000000000 R09: 0000000000000000
> R10: ffffffff81b47eab R11: 0000000000000000 R12: ffff88801e231210
> R13: 0000000020400000 R14: ffff8880738f8700 R15: 0000000000000000
> FS:  00007f1a19594700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f33cc0df300 CR3: 000000001ca70000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
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> 
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