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Date:   Tue, 6 Sep 2022 17:22:18 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     syzbot <syzbot+6b3a1fd733d73b7a14d7@syzkaller.appspotmail.com>
Cc:     linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        linux-usb@vger.kernel.org, syzkaller-bugs@googlegroups.com,
        Jason Gunthorpe <jgg@nvidia.com>,
        John Hubbard <jhubbard@nvidia.com>,
        Alistair Popple <apopple@nvidia.com>,
        Ralph Campbell <rcampbell@nvidia.com>,
        Alex Sierra <alex.sierra@amd.com>,
        Dan Williams <dan.j.williams@intel.com>
Subject: Re: [syzbot] usb-testing boot error: BUG: unable to handle kernel
 paging request in follow_page_mask
Message-Id: <20220906172218.b50521a3caf73095983a907e@linux-foundation.org>
In-Reply-To: <00000000000098580e05e8033b9a@google.com>
References: <00000000000098580e05e8033b9a@google.com>
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(cc some of the gup.c developers)

On Tue, 06 Sep 2022 07:44:25 -0700 syzbot <syzbot+6b3a1fd733d73b7a14d7@syzkaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    4e55e22d3d9a USB: hcd-pci: Drop the unused id parameter fr..
> git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
> console output: https://syzkaller.appspot.com/x/log.txt?x=16b2d4d7080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3cb39b084894e9a5
> dashboard link: https://syzkaller.appspot.com/bug?extid=6b3a1fd733d73b7a14d7
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/05f931abacee/disk-4e55e22d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/9b749a498398/vmlinux-4e55e22d.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+6b3a1fd733d73b7a14d7@syzkaller.appspotmail.com
> 
> BUG: unable to handle page fault for address: ffffeefda00001ff

Thanks.  A bit strange that it came from the USB tree, but I assume this
bug originates from Linus's current.

> #PF: supervisor read access in kernel mode
> #PF: error_code(0x0000) - not-present page
> PGD 0 P4D 0 
> Oops: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 687 Comm: kworker/u4:0 Not tainted 6.0.0-rc1-syzkaller-00049-g4e55e22d3d9a #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
> RIP: 0010:native_pud_val arch/x86/include/asm/pgtable_types.h:347 [inline]
> RIP: 0010:pud_none arch/x86/include/asm/pgtable.h:829 [inline]
> RIP: 0010:follow_pud_mask mm/gup.c:730 [inline]
> RIP: 0010:follow_p4d_mask mm/gup.c:782 [inline]
> RIP: 0010:follow_page_mask+0x1a9/0x1c90 mm/gup.c:846
> Code: 00 80 88 ff ff 4c 01 e8 4d 89 e5 49 c1 ed 1b 41 81 e5 f8 0f 00 00 49 01 c5 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 d4 18 00 00 4d 8b 75 00 31 ff 49 83 e6 9f 4c 89
> RSP: 0000:ffffc90001e7fb10 EFLAGS: 00010a06
> RAX: dffffc0000000000 RBX: ffff88810e732500 RCX: 0000000000000000
> RDX: 1ffff2fda00001ff RSI: ffffffff8167fdbd RDI: 0000000000000007
> RBP: ffffc90001e7fc48 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 00007fffffffefc0
> R13: ffff97ed00000ff8 R14: 0000000000000000 R15: 0000000000002017
> FS:  0000000000000000(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffeefda00001ff CR3: 0000000007825000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <TASK>
>  __get_user_pages+0x3f2/0x1020 mm/gup.c:1193
>  __get_user_pages_locked mm/gup.c:1399 [inline]
>  __get_user_pages_remote+0x18f/0x830 mm/gup.c:2109
>  get_user_pages_remote+0x84/0xc0 mm/gup.c:2182
>  get_arg_page+0xe4/0x2a0 fs/exec.c:222
>  copy_string_kernel+0x169/0x460 fs/exec.c:639
>  copy_strings_kernel+0xb3/0x190 fs/exec.c:655
>  kernel_execve+0x377/0x500 fs/exec.c:2001
>  call_usermodehelper_exec_async+0x2e3/0x580 kernel/umh.c:112
>  ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
>  </TASK>
> Modules linked in:
> CR2: ffffeefda00001ff
> ---[ end trace 0000000000000000 ]---
> RIP: 0010:native_pud_val arch/x86/include/asm/pgtable_types.h:347 [inline]
> RIP: 0010:pud_none arch/x86/include/asm/pgtable.h:829 [inline]
> RIP: 0010:follow_pud_mask mm/gup.c:730 [inline]
> RIP: 0010:follow_p4d_mask mm/gup.c:782 [inline]
> RIP: 0010:follow_page_mask+0x1a9/0x1c90 mm/gup.c:846
> Code: 00 80 88 ff ff 4c 01 e8 4d 89 e5 49 c1 ed 1b 41 81 e5 f8 0f 00 00 49 01 c5 48 b8 00 00 00 00 00 fc ff df 4c 89 ea 48 c1 ea 03 <80> 3c 02 00 0f 85 d4 18 00 00 4d 8b 75 00 31 ff 49 83 e6 9f 4c 89
> RSP: 0000:ffffc90001e7fb10 EFLAGS: 00010a06
> RAX: dffffc0000000000 RBX: ffff88810e732500 RCX: 0000000000000000
> RDX: 1ffff2fda00001ff RSI: ffffffff8167fdbd RDI: 0000000000000007
> RBP: ffffc90001e7fc48 R08: 0000000000000007 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000000 R12: 00007fffffffefc0
> R13: ffff97ed00000ff8 R14: 0000000000000000 R15: 0000000000002017
> FS:  0000000000000000(0000) GS:ffff8881f6900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffeefda00001ff CR3: 0000000007825000 CR4: 00000000003506e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> ----------------
> Code disassembly (best guess):
>    0:	00 80 88 ff ff 4c    	add    %al,0x4cffff88(%rax)
>    6:	01 e8                	add    %ebp,%eax
>    8:	4d 89 e5             	mov    %r12,%r13
>    b:	49 c1 ed 1b          	shr    $0x1b,%r13
>    f:	41 81 e5 f8 0f 00 00 	and    $0xff8,%r13d
>   16:	49 01 c5             	add    %rax,%r13
>   19:	48 b8 00 00 00 00 00 	movabs $0xdffffc0000000000,%rax
>   20:	fc ff df
>   23:	4c 89 ea             	mov    %r13,%rdx
>   26:	48 c1 ea 03          	shr    $0x3,%rdx
> * 2a:	80 3c 02 00          	cmpb   $0x0,(%rdx,%rax,1) <-- trapping instruction
>   2e:	0f 85 d4 18 00 00    	jne    0x1908
>   34:	4d 8b 75 00          	mov    0x0(%r13),%r14
>   38:	31 ff                	xor    %edi,%edi
>   3a:	49 83 e6 9f          	and    $0xffffffffffffff9f,%r14
>   3e:	4c                   	rex.WR
>   3f:	89                   	.byte 0x89
> 
> 
> ---
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