linux-kernel - Re: [PATCH] ubifs: skip dumping tnc tree when zroot is null

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Message-ID: <c929d4b4-44b8-810f-2014-98cd1ea0d392@huawei.com>
Date: Tue, 24 Dec 2024 16:44:41 +0800
From: Zhihao Cheng <chengzhihao1@...wei.com>
To: pangliyuan <pangliyuan1@...wei.com>, <richard@....at>,
	<Artem.Bityutskiy@...ia.com>, <ext-adrian.hunter@...ia.com>
CC: <linux-mtd@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<wangfangpeng1@...wei.com>
Subject: Re: [PATCH] ubifs: skip dumping tnc tree when zroot is null

在 2024/12/24 16:18, pangliyuan 写道:
> Clearing slab cache will free all znode in memory and make
> c->zroot.znode = NULL, then dumping tnc tree will access
> c->zroot.znode which cause null pointer dereference.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219624#c0
> Fixes: 1e51764a3c2a ("UBIFS: add new flash file system")
> Signed-off-by: pangliyuan <pangliyuan1@...wei.com>
> ---
>   fs/ubifs/debug.c | 22 +++++++++++++---------
>   1 file changed, 13 insertions(+), 9 deletions(-)
> 

Reviewed-by: Zhihao Cheng <chengzhihao1@...wei.com>
> diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
> index 5cc69beaa62e..10a86c02a8b3 100644
> --- a/fs/ubifs/debug.c
> +++ b/fs/ubifs/debug.c
> @@ -946,16 +946,20 @@ void ubifs_dump_tnc(struct ubifs_info *c)
>   
>   	pr_err("\n");
>   	pr_err("(pid %d) start dumping TNC tree\n", current->pid);
> -	znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, NULL);
> -	level = znode->level;
> -	pr_err("== Level %d ==\n", level);
> -	while (znode) {
> -		if (level != znode->level) {
> -			level = znode->level;
> -			pr_err("== Level %d ==\n", level);
> +	if (c->zroot.znode) {
> +		znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, NULL);
> +		level = znode->level;
> +		pr_err("== Level %d ==\n", level);
> +		while (znode) {
> +			if (level != znode->level) {
> +				level = znode->level;
> +				pr_err("== Level %d ==\n", level);
> +			}
> +			ubifs_dump_znode(c, znode);
> +			znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, znode);
>   		}
> -		ubifs_dump_znode(c, znode);
> -		znode = ubifs_tnc_levelorder_next(c, c->zroot.znode, znode);
> +	} else {
> +		pr_err("empty TNC tree in memory\n");
>   	}
>   	pr_err("(pid %d) finish dumping TNC tree\n", current->pid);
>   }
>