linux-kernel - Re: [dm-devel] [PATCH][RFC] dm raid: Fix NULL pointer dereference for raid1 without bitmap

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Date:   Thu, 30 Mar 2017 21:30:53 +0200
From:   Heinz Mauelshagen <heinzm@...hat.com>
To:     kmeaw@...dex-team.ru, linux-kernel <linux-kernel@...r.kernel.org>,
        dm-devel@...hat.com, linux-raid@...r.kernel.org
Cc:     Андрей Сметанин 
        <asmetanin@...dex-team.ru>, shli@...nel.org, agk@...hat.com
Subject: Re: [dm-devel] [PATCH][RFC] dm raid: Fix NULL pointer dereference for
 raid1 without bitmap


Acked-by: Heinz Mauelshagen <heinzm@...hat.com>

This is the simplest way to solve the issue at hand
(bitmap_load() returns success with non-existing bitmap).

Heinz

On 03/30/2017 05:14 PM, kmeaw@...dex-team.ru wrote:
> From: Dmitry Bilunov <kmeaw@...dex-team.ru>
>
> 4257e08 introduces a bitmap resize call during preresume phase. User
> can create a DM device with "raid" target configured as raid1 with no
> metadata devices to hold superblock/bitmap info. It can be achieved
> using the following sequence:
>
>    truncate -s 32M /dev/shm/raid-test
>    LOOP=$(losetup --show -f /dev/shm/raid-test)
>    dmsetup create raid-test-linear0 --table "0 1024 linear $LOOP 0"
>    dmsetup create raid-test-linear1 --table "0 1024 linear $LOOP 1024"
>    dmsetup create raid-test --table "0 1024 raid raid1 1 2048 2 - /dev/mapper/raid-test-linear0 - /dev/mapper/raid-test-linear1"
>
> It results in
>
> Killed
> [ 4029.110216] device-mapper: raid: Ignoring chunk size parameter for RAID 1
> [ 4029.110217] device-mapper: raid: Choosing default region size of 4MiB
> [ 4029.111349] md/raid1:mdX: active with 2 out of 2 mirrors
> [ 4029.114770] BUG: unable to handle kernel NULL pointer dereference at 0000000000000030
> [ 4029.114802] IP: bitmap_resize+0x25/0x7c0 [md_mod]
> [ 4029.114816] PGD 0
> …
> [ 4029.115059] Hardware name: Aquarius Pro P30 S85 BUY-866/B85M-E, BIOS 2304 05/25/2015
> [ 4029.115079] task: ffff88015cc29a80 task.stack: ffffc90001a5c000
> [ 4029.115097] RIP: 0010:bitmap_resize+0x25/0x7c0 [md_mod]
> [ 4029.115112] RSP: 0018:ffffc90001a5fb68 EFLAGS: 00010246
> [ 4029.115127] RAX: 0000000000000005 RBX: 0000000000000000 RCX: 0000000000000000
> [ 4029.115146] RDX: 0000000000000000 RSI: 0000000000000400 RDI: 0000000000000000
> [ 4029.115166] RBP: ffffc90001a5fc28 R08: 0000000800000000 R09: 00000008ffffffff
> [ 4029.115185] R10: ffffea0005661600 R11: ffff88015cc29a80 R12: ffff88021231f058
> [ 4029.115204] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
> [ 4029.115223] FS:  00007fe73a6b4740(0000) GS:ffff88021ea80000(0000) knlGS:0000000000000000
> [ 4029.115245] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 4029.115261] CR2: 0000000000000030 CR3: 0000000159a74000 CR4: 00000000001426e0
> [ 4029.115281] Call Trace:
> [ 4029.115291]  ? raid_iterate_devices+0x63/0x80 [dm_raid]
> [ 4029.115309]  ? dm_table_all_devices_attribute.isra.23+0x41/0x70 [dm_mod]
> [ 4029.115329]  ? dm_table_set_restrictions+0x225/0x2d0 [dm_mod]
> [ 4029.115346]  raid_preresume+0x81/0x2e0 [dm_raid]
> [ 4029.115361]  dm_table_resume_targets+0x47/0xe0 [dm_mod]
> [ 4029.115378]  dm_resume+0xa8/0xd0 [dm_mod]
> [ 4029.115391]  dev_suspend+0x123/0x250 [dm_mod]
> [ 4029.115405]  ? table_load+0x350/0x350 [dm_mod]
> [ 4029.115419]  ctl_ioctl+0x1c2/0x490 [dm_mod]
> [ 4029.115433]  dm_ctl_ioctl+0xe/0x20 [dm_mod]
> [ 4029.115447]  do_vfs_ioctl+0x8d/0x5a0
> [ 4029.115459]  ? ____fput+0x9/0x10
> [ 4029.115470]  ? task_work_run+0x79/0xa0
> [ 4029.115481]  SyS_ioctl+0x3c/0x70
> [ 4029.115493]  entry_SYSCALL_64_fastpath+0x13/0x94
>
> Function raid_preresume takes an assumption that raid_set has a bitmap enabled.
> Call to bitmap_load(&rs->md) inside __load_dirty_region_bitmap would return 0 even
> if there is no bitmap present.
>
> This patch avoids resizing an absent bitmap.
>
> Signed-off-by: Dmitry Bilunov <kmeaw@...dex-team.ru>
> Signed-off-by: Andrey Smetanin <asmetanin@...dex-team.ru>
> ---
>   drivers/md/dm-raid.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index f8564d63..67a5405e 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -3727,6 +3727,7 @@ static int raid_preresume(struct dm_target *ti)
>   
>   	/* Resize bitmap to adjust to changed region size (aka MD bitmap chunksize) */
>   	if (test_bit(RT_FLAG_RS_BITMAP_LOADED, &rs->runtime_flags) &&
> +	    mddev->bitmap &&
>   	    mddev->bitmap_info.chunksize != to_bytes(rs->requested_bitmap_chunk_sectors)) {
>   		r = bitmap_resize(mddev->bitmap, mddev->dev_sectors,
>   				  to_bytes(rs->requested_bitmap_chunk_sectors), 0);