Messages in this thread | | | From | "Rafael J. Wysocki" <> | Date | Thu, 21 Oct 2021 19:17:20 +0200 | Subject | Re: [PATCH -next] PM: hibernate: Get block device exclusively when do swsusp_check |
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On Thu, Oct 21, 2021 at 4:38 PM yebin <yebin10@huawei.com> wrote: > > > > 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.
I see.
> 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.
Yes, it is invalid to call swsusp_check() without a hibernation image in the target swap partition or swap file if that's what you mean.
However, in the case of a swap file, the image may be there in theory even if the filesystem holding the swap file is mounted.
> I refer to the process of swapon. If the swap partition is a block > device, it is also > opened exclusively. > > swapon > claim_swapfile
There are two cases, though, the S_ISBLK() one and the S_ISREG() one, and the latter is the swap file case I believe.
> 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;
Here, it is not exclusive.
Anyway, I think that the change made by the patch should be fine, because it mostly affects restore and I'm not expecting anyone to restore the system from an image in a swap file while the filesystem holding it is mounted.
So I'm going to apply it with some changelog edits.
Thanks!
> } > > 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 { > >>>> -- > >>> . > >>> > > . > > >
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