MIME-Version: 1.0
Date:   Mon, 15 Nov 2021 00:15:52 -0800
In-Reply-To: <CAEVVKH8FXmthqxmEP_0qhpT7uqfzgWhWAmJbKNEznm0TN6TmQw@mail.gmail.com>
Message-ID: <000000000000ce677205d0cf6a87@google.com>
Subject: Re: [syzbot] WARNING in __get_free_pages
From:   syzbot <syzbot+23a02c7df2cf2bc93fa2@syzkaller.appspotmail.com>
To:     Xiongwei Song <sxwjean@gmail.com>
Cc:     akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, sxwjean@gmail.com,
        syzkaller-bugs@googlegroups.com
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

> #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

This crash does not have a reproducer. I cannot test it.

> 8ab77458790
>
> commit 0921cbb7e62f2aac73da86fff458814d9b0a846b (HEAD)
> Author: Xiongwei Song <sxwjean@gmail.com>
> Date:   Mon Nov 15 16:06:19 2021 +0800
>
>     floppy: Add max size check for user space request
>
>     We need to check the max request size that is from user space before
>     allocating pages. If the request size exceeds the limit, return -EINVAL.
>
>     Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
>
> diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
> index c4267da716fe..52112ed59dd0 100644
> --- a/drivers/block/floppy.c
> +++ b/drivers/block/floppy.c
> @@ -3081,6 +3081,8 @@ static void raw_cmd_free(struct floppy_raw_cmd **ptr)
>         }
>  }
>
> +#define MAX_LEN (1UL << MAX_ORDER << PAGE_SHIFT)
> +
>  static int raw_cmd_copyin(int cmd, void __user *param,
>                                  struct floppy_raw_cmd **rcmd)
>  {
> @@ -3108,7 +3110,7 @@ static int raw_cmd_copyin(int cmd, void __user *param,
>         ptr->resultcode = 0;
>
>         if (ptr->flags & (FD_RAW_READ | FD_RAW_WRITE)) {
> -               if (ptr->length <= 0)
> +               if (ptr->length <= 0 || ptr->length >= MAX_LEN)
>                         return -EINVAL;
>                 ptr->kernel_data = (char *)fd_dma_mem_alloc(ptr->length);
>                 fallback_on_nodma_alloc(&ptr->kernel_data, ptr->length);
>
>
> Regards,
> Xiongwei
>
> On Sun, Nov 14, 2021 at 11:37 AM syzbot
> <syzbot+23a02c7df2cf2bc93fa2@syzkaller.appspotmail.com> wrote:
>>
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    debe436e77c7 Merge tag 'ext4_for_linus' of git://git.kerne..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=10bca72ab00000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=9d7259f0deb293aa
>> dashboard link: https://syzkaller.appspot.com/bug?extid=23a02c7df2cf2bc93fa2
>> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>> userspace arch: i386
>>
>> 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+23a02c7df2cf2bc93fa2@syzkaller.appspotmail.com
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 3 PID: 16525 at mm/page_alloc.c:5344 current_gfp_context include/linux/sched/mm.h:195 [inline]
>> WARNING: CPU: 3 PID: 16525 at mm/page_alloc.c:5344 __alloc_pages+0x45d/0x500 mm/page_alloc.c:5356
>> Modules linked in:
>> CPU: 3 PID: 16525 Comm: syz-executor.3 Not tainted 5.15.0-syzkaller #0
>> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.14.0-2 04/01/2014
>> RIP: 0010:__alloc_pages+0x45d/0x500 mm/page_alloc.c:5344
>> Code: be c9 00 00 00 48 c7 c7 20 4a 97 89 c6 05 62 32 a7 0b 01 e8 74 9a 42 07 e9 6a ff ff ff 0f 0b e9 a0 fd ff ff 40 80 e5 3f eb 88 <0f> 0b e9 18 ff ff ff 4c 89 ef 44 89 e6 45 31 ed e8 1e 76 ff ff e9
>> RSP: 0018:ffffc90023b87850 EFLAGS: 00010246
>> RAX: 0000000000000000 RBX: 1ffff92004770f0b RCX: dffffc0000000000
>> RDX: 0000000000000000 RSI: 0000000000000033 RDI: 0000000000010cc1
>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000001
>> R10: ffffffff81bb4686 R11: 0000000000000001 R12: ffffffff902c1960
>> R13: 0000000000000033 R14: 0000000000000000 R15: ffff88804cf64a30
>> FS:  0000000000000000(0000) GS:ffff88802cd00000(0063) knlGS:00000000f44b4b40
>> CS:  0010 DS: 002b ES: 002b CR0: 0000000080050033
>> CR2: 000000002c921000 CR3: 000000004f507000 CR4: 0000000000150ee0
>> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> Call Trace:
>>  <TASK>
>>  alloc_pages+0x1a7/0x300 mm/mempolicy.c:2191
>>  __get_free_pages+0x8/0x40 mm/page_alloc.c:5418
>>  raw_cmd_copyin drivers/block/floppy.c:3113 [inline]
>>  raw_cmd_ioctl drivers/block/floppy.c:3160 [inline]
>>  fd_locked_ioctl+0x12e5/0x2820 drivers/block/floppy.c:3528
>>  fd_ioctl drivers/block/floppy.c:3555 [inline]
>>  fd_compat_ioctl+0x891/0x1b60 drivers/block/floppy.c:3869
>>  compat_blkdev_ioctl+0x3b8/0x810 block/ioctl.c:662
>>  __do_compat_sys_ioctl+0x1c7/0x290 fs/ioctl.c:972
>>  do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline]
>>  __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178
>>  do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203
>>  entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
>> RIP: 0023:0xf6eba549
>> Code: 03 74 c0 01 10 05 03 74 b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
>> RSP: 002b:00000000f44b45fc EFLAGS: 00000296 ORIG_RAX: 0000000000000036
>> RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000000258
>> RDX: 0000000020000400 RSI: 0000000000000000 RDI: 0000000000000000
>> RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
>> R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
>> R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
>>  </TASK>
>> ----------------
>> Code disassembly (best guess):
>>    0:   03 74 c0 01             add    0x1(%rax,%rax,8),%esi
>>    4:   10 05 03 74 b8 01       adc    %al,0x1b87403(%rip)        # 0x1b8740d
>>    a:   10 06                   adc    %al,(%rsi)
>>    c:   03 74 b4 01             add    0x1(%rsp,%rsi,4),%esi
>>   10:   10 07                   adc    %al,(%rdi)
>>   12:   03 74 b0 01             add    0x1(%rax,%rsi,4),%esi
>>   16:   10 08                   adc    %cl,(%rax)
>>   18:   03 74 d8 01             add    0x1(%rax,%rbx,8),%esi
>>   1c:   00 00                   add    %al,(%rax)
>>   1e:   00 00                   add    %al,(%rax)
>>   20:   00 51 52                add    %dl,0x52(%rcx)
>>   23:   55                      push   %rbp
>>   24:   89 e5                   mov    %esp,%ebp
>>   26:   0f 34                   sysenter
>>   28:   cd 80                   int    $0x80
>> * 2a:   5d                      pop    %rbp <-- trapping instruction
>>   2b:   5a                      pop    %rdx
>>   2c:   59                      pop    %rcx
>>   2d:   c3                      retq
>>   2e:   90                      nop
>>   2f:   90                      nop
>>   30:   90                      nop
>>   31:   90                      nop
>>   32:   8d b4 26 00 00 00 00    lea    0x0(%rsi,%riz,1),%esi
>>   39:   8d b4 26 00 00 00 00    lea    0x0(%rsi,%riz,1),%esi
>>
>>
>> ---
>> 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@googlegroups.com.
>>
>> syzbot will keep track of this issue. See:
>> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>>
>> --
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