linux-kernel - Re: [syzbot] [bcachefs?] BUG: unable to handle kernel paging request in bch2_opt_to

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Message-ID: <Zuzf7hg_5aOZ7LJl@inml.grue.cc>
Date: Fri, 20 Sep 2024 12:37:34 +1000
From: AP <lkml@...l.grue.cc>
To: Edward Adam Davis <eadavis@...com>
Cc: syzbot+294f528e56138c357a48@...kaller.appspotmail.com,
	kent.overstreet@...ux.dev, linux-bcachefs@...r.kernel.org,
	linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bcachefs?] BUG: unable to handle kernel paging request
 in bch2_opt_to_text

On Thu, Sep 19, 2024 at 11:11:40PM +0800, Edward Adam Davis wrote:
> The format of the 'name=value' key value pair included in the options is
> incorrect, if only name is present.
> 
> #syz test
> 
> diff --git a/fs/bcachefs/opts.c b/fs/bcachefs/opts.c
> index e10fc1da71b1..5616dc8570fa 100644
> --- a/fs/bcachefs/opts.c
> +++ b/fs/bcachefs/opts.c
> @@ -472,6 +472,12 @@ int bch2_parse_one_mount_opt(struct bch_fs *c, struct bch_opts *opts,
>  	u64 v;
>  	int ret, id;
>  
> +	if (!val) {
> +		pr_err("Bad mount option, value is NULL");

Given that this would be user visible, NULL is unlikely to mean much. I believe that it
would be better to state "value is missing but required." or similar. This clearly tells
the user how they erred regardless of their programming knowledge.

AP