Re: [PATCH -next] PM: hibernate: Get block device exclusively when do swsusp_check

yebin
2021-10-21T14:38:29Z

On 2021/10/21 21:27, Rafael J. Wysocki wrote:
> On Thu, Oct 21, 2021 at 1:38 PM yebin <yebin10@huawei.com> wrote:
>>
>>
>> On 2021/10/21 19:00, Rafael J. Wysocki wrote:
>>> On Wed, Oct 13, 2021 at 2:06 PM Ye Bin <yebin10@huawei.com> wrote:
>>>> We got follow issue:
>>>> [ 89.266592] ------------[ cut here ]------------
>>>> [ 89.267427] kernel BUG at fs/buffer.c:3020!
>>>> [ 89.268264] invalid opcode: 0000 [#1] SMP KASAN PTI
>>>> [ 89.269116] CPU: 7 PID: 1750 Comm: kmmpd-loop0 Not tainted 5.10.0-862.14.0.6.x86_64-08610-gc932cda3cef4-dirty #20
>>>> [ 89.273169] RIP: 0010:submit_bh_wbc.isra.0+0x538/0x6d0
>>>> [ 89.277157] RSP: 0018:ffff888105ddfd08 EFLAGS: 00010246
>>>> [ 89.278093] RAX: 0000000000000005 RBX: ffff888124231498 RCX: ffffffffb2772612
>>>> [ 89.279332] RDX: 1ffff11024846293 RSI: 0000000000000008 RDI: ffff888124231498
>>>> [ 89.280591] RBP: ffff8881248cc000 R08: 0000000000000001 R09: ffffed1024846294
>>>> [ 89.281851] R10: ffff88812423149f R11: ffffed1024846293 R12: 0000000000003800
>>>> [ 89.283095] R13: 0000000000000001 R14: 0000000000000000 R15: ffff8881161f7000
>>>> [ 89.284342] FS: 0000000000000000(0000) GS:ffff88839b5c0000(0000) knlGS:0000000000000000
>>>> [ 89.285711] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>> [ 89.286701] CR2: 00007f166ebc01a0 CR3: 0000000435c0e000 CR4: 00000000000006e0
>>>> [ 89.287919] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>>>> [ 89.289138] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>>>> [ 89.290368] Call Trace:
>>>> [ 89.290842] write_mmp_block+0x2ca/0x510
>>>> [ 89.292218] kmmpd+0x433/0x9a0
>>>> [ 89.294902] kthread+0x2dd/0x3e0
>>>> [ 89.296268] ret_from_fork+0x22/0x30
>>>> [ 89.296906] Modules linked in:
>>>>
>>>> We can reproduce this issue as follow:
>>>> 1. mkfs.ext4 -O mmp /dev/sda -b 1024
>>>> 2. mount /dev/sda /home/test
>>>> 3. echo "/dev/sda" > /sys/power/resume
>>>> 4. wait a moment we will get exception
>>>>
>>>> The sequence of issue is as follows:
>>>> Thread1 Thread2
>>>> mount /dev/sda /home/test
>>>> get s_mmp_bh --> has mapped flag
>>>> start kmmpd thread
>>>> echo "/dev/sda" > /sys/power/resume
>>>> resume_store
>>>> software_resume
>>>> swsusp_check
>>>> set_blocksize
>>>> truncate_inode_pages_range
>>>> truncate_cleanup_page
>>>> block_invalidatepage
>>>> discard_buffer --> clean mapped flag
>>>> write_mmp_block
>>>> submit_bh
>>>> submit_bh_wbc
>>>> BUG_ON(!buffer_mapped(bh)) --> trigger bug_on
>>>>
>>>> To solve this issue, get block device exclusively when do swsusp_check.
>>> And why exactly is this going to help?
>> If a block device is already mounted, then do resume, it will discard
>> buffer
>> which file system being used. That can cause the file system to crash and
>> may even cause the system to reset abnormally.
> I see.
>
> Is there a way to indicate in swsusp_check() that the access will be
> read-only and so it doesn't care whether or not the block device is in
> use by someone else?
The root reason is that call 'set_blocksize' in 'swsusp_check' which
maybe invalidate
block device's page.
Moreover, the file system and swap partition share storage space, which
will lead to
data confusion.
>> If the "/sys/power/resume" sysfs interface is unrestricted, it will provide
>> criminals with a way to attack the system.
>>
>>>> Signed-off-by: Ye Bin <yebin10@huawei.com>
>>>> ---
>>>> kernel/power/swap.c | 5 +++--
>>>> 1 file changed, 3 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/kernel/power/swap.c b/kernel/power/swap.c
>>>> index 9ec418955556..26c0bd2a50da 100644
>>>> --- a/kernel/power/swap.c
>>>> +++ b/kernel/power/swap.c
>>>> @@ -1521,9 +1521,10 @@ int swsusp_read(unsigned int *flags_p)
>>>> int swsusp_check(void)
>>>> {
>>>> int error;
>>>> + void *holder;
>>>>
>>>> hib_resume_bdev = blkdev_get_by_dev(swsusp_resume_device,
>>>> - FMODE_READ, NULL);
>>>> + FMODE_READ | FMODE_EXCL, &holder);
>>> So you need to explain to me how this works.
>> As we call 'blkdev_get_by_path' in 'mount_bdev' pass mode includes
>> FMODE_EXCL.
>> So if 'swsusp_check' try to get block device with mode includes
>> FMODE_EXCL will failed.
>>
>> I think if a block device is used as a swap partition, it cannot be
>> mounted at the
>> same time. Conversely, if a block device is already mounted, it cannot
>> be used as
>> a swap partition.
> Well, what if a hibernation image is located in a swap file? This is
> one of the cases that need to be supported.
I don't know much about this, but I think the process can call
swsusp_check, the
hibernation image must be loaded into the block device.

I refer to the process of swapon. If the swap partition is a block
device, it is also
opened exclusively.
swapon
claim_swapfile
static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
{
int error;

if (S_ISBLK(inode->i_mode)) { -->If a block device is
specified, it is also opened exclusively here.
p->bdev = blkdev_get_by_dev(inode->i_rdev,
FMODE_READ | FMODE_WRITE |
FMODE_EXCL, p);
if (IS_ERR(p->bdev)) {
error = PTR_ERR(p->bdev);
p->bdev = NULL;
return error;
}
p->old_block_size = block_size(p->bdev);
error = set_blocksize(p->bdev, PAGE_SIZE);
if (error < 0)
return error;
/*
* Zoned block devices contain zones that have a sequential
* write only restriction. Hence zoned block devices
are not
* suitable for swapping. Disallow them here.
*/
if (blk_queue_is_zoned(p->bdev->bd_disk->queue))
return -EINVAL;
p->flags |= SWP_BLKDEV;
} else if (S_ISREG(inode->i_mode)) {
p->bdev = inode->i_sb->s_bdev;
}

return 0;
}
>>>> if (!IS_ERR(hib_resume_bdev)) {
>>>> set_blocksize(hib_resume_bdev, PAGE_SIZE);
>>>> clear_page(swsusp_header);
>>>> @@ -1545,7 +1546,7 @@ int swsusp_check(void)
>>>>
>>>> put:
>>>> if (error)
>>>> - blkdev_put(hib_resume_bdev, FMODE_READ);
>>>> + blkdev_put(hib_resume_bdev, FMODE_READ | FMODE_EXCL);
>>>> else
>>>> pr_debug("Image signature found, resuming\n");
>>>> } else {
>>>> --
>>> .
>>>
> .
>