linux-kernel - Re: [PATCH v2] ubi: gluebi: Fix NULL pointer dereference caused by ftl notifier

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Date: Mon, 17 Jun 2024 20:09:06 +0200 (CEST)
From: Richard Weinberger <richard@....at>
To: Gagan Sidhu <broly@....com>
Cc: ZhaoLong Wang <wangzhaolong1@...wei.com>, 
	chengzhihao1 <chengzhihao1@...wei.com>, 
	dpervushin <dpervushin@...eddedalley.com>, 
	linux-kernel <linux-kernel@...r.kernel.org>, 
	linux-mtd <linux-mtd@...ts.infradead.org>, 
	Miquel Raynal <miquel.raynal@...tlin.com>, 
	Vignesh Raghavendra <vigneshr@...com>, 
	yangerkun <yangerkun@...wei.com>, yi zhang <yi.zhang@...wei.com>
Subject: Re: [PATCH v2] ubi: gluebi: Fix NULL pointer dereference caused by
 ftl notifier

----- Ursprüngliche Mail -----
> Von: "Gagan Sidhu" <broly@....com>
> https://github.com/torvalds/linux/blob/master/drivers/mtd/ubi/gluebi.c#L297
> 
> it seems the GLUEBI is setting the mtd to MTD_UBIVOLUME
> 
> https://github.com/torvalds/linux/blob/master/drivers/mtd/ubi/block.c
> 
> where this doesn’t even have the text “mtd” anywhere.
> 
> but the boot partition is always the ubiblock device.
> 
> so is gluebi taking the same volume and adding the MTD_UBIVOLUME label or
> something?

Yes, GLUEBI emulates a MTD on top of an UBI volume.
It sets the MTD device type to MTD_UBIVOLUME.

>> 
>> [    5.462504] auto-attach mtd7
>> [    5.462525] ubi0: default fastmap pool size: 15
>> [    5.477309] ubi0: default fastmap WL pool size: 7
>> [    5.486683] ubi0: attaching mtd7
>> [    5.811240] UBI: EOF marker found, PEBs from 273 will be erased
>> [    5.811299] ubi0: scanning is finished
>> [    5.874546] gluebi (pid 1): gluebi_resized: got update notification for
>> unknown UBI device 0 volume 1
>> [    5.892927] ubi0: volume 1 ("rootfs_data") re-sized from 9 to 28 LEBs
>> [    5.906683] ubi0: attached mtd7 (name "ubi", size 40 MiB)
>> [    5.917446] ubi0: PEB size: 131072 bytes (128 KiB), LEB size: 126976 bytes
>> [    5.931132] ubi0: min./max. I/O unit sizes: 2048/2048, sub-page size 2048
>> [    5.944654] ubi0: VID header offset: 2048 (aligned 2048), data offset: 4096
>> [    5.958513] ubi0: good PEBs: 320, bad PEBs: 0, corrupted PEBs: 0
>> [    5.970472] ubi0: user volume: 2, internal volumes: 1, max. volumes count:
>> 128
>> [    5.984859] ubi0: max/mean erase counter: 1/0, WL threshold: 4096, image
>> sequence number: 1613475955
>> [    6.003045] ubi0: available PEBs: 0, total reserved PEBs: 320, PEBs reserved
>> for bad PEB handling: 15
>> [    6.021426] rootfs: parsing partitions cmdlinepart
>> [    6.021444] ubi0: background thread "ubi_bgt0d" started, PID 97
>> [    6.043694] rootfs: got parser (null)
>> [    6.051426] mtd: device 12 (rootfs) set to be root filesystem

AFAICT, this log line is not part of the mainline kernel.

>> [    6.062891] rootfs_data: parsing partitions cmdlinepart
>> [    6.073669] rootfs_data: got parser (null)
>> [    6.211240] block ubiblock0_0: created from ubi0:0(rootfs)
>> [    6.259545] rtc-pcf8563 0-0051: hctosys: unable to read the hardware clock
>> [    6.282125] VFS: Cannot open root device "(null)" or unknown-block(31,12):
>> error -6
>> [    6.297406] Please append a correct "root=" boot option; here are the
>> available partitions:
>> [    6.314054] 1f00             512 mtdblock0
>> [    6.314060]  (driver?)
>> [    6.327077] 1f01             256 mtdblock1
>> [    6.327081]  (driver?)
>> [    6.340101] 1f02             256 mtdblock2
>> [    6.340105]  (driver?)
>> [    6.353124] 1f03             256 mtdblock3
>> [    6.353129]  (driver?)
>> [    6.366153] 1f04           45056 mtdblock4
>> [    6.366158]  (driver?)
>> [    6.379175] 1f05           40572 mtdblock5
>> [    6.379179]  (driver?)
>> [    6.392217] 1f06            4096 mtdblock6
>> [    6.392222]  (driver?)
>> [    6.405240] 1f07           40960 mtdblock7
>> [    6.405244]  (driver?)
>> [    6.418272] 1f08           32768 mtdblock8
>> [    6.418277]  (driver?)
>> [    6.431296] 1f09           40960 mtdblock9
>> [    6.431300]  (driver?)
>> [    6.444324] 1f0a            6144 mtdblock10
>> [    6.444328]  (driver?)
>> [    6.457518] 1f0b            4608 mtdblock11
>> [    6.457523]  (driver?)
>> [    6.470720] fe00           33604 ubiblock0_0
>> [    6.470724]  (driver?)
>> [    6.484090] Kernel panic - not syncing: VFS: Unable to mount root fs on
>> unknown-block(31,12)

(31, 12) would be mtdblock12.
How does your kernel know that mtdblock12 shall be the rootfs?

I have a hard time understanding your current setup.

Thanks,
//richard