linux-kernel - Re: [PATCH] um: ubd: Fix crash from option parsing

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Message-ID: <871regg4g8.fsf@collabora.com>
Date:   Tue, 19 Jan 2021 15:35:35 -0300
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Paul Lawrence <paullawrence@...gle.com>
Cc:     Jeff Dike <jdike@...toit.com>, Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Christopher Obbard <chris.obbard@...labora.com>,
        linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] um: ubd: Fix crash from option parsing

Paul Lawrence <paullawrence@...gle.com> writes:

> Below patch will cause NULL ptr dereferences if the optional filenames
> are not present.
>
> Fixes: ef3ba87cb7c9 (um: ubd: Set device serial attribute from cmdline)
> Signed-off-by: Paul Lawrence <paullawrence@...gle.com>

Looks good.

Reviewed-by: Gabriel Krisman Bertazi <krisman@...labora.com>

Totally unrelated, but it seems the original patch writes a "(null)"
string to the sysfs attribute, if no serial is defined.  I think we
should have a default serial UBDX in case the user didn't provide any.

Thanks,

> ---
>  arch/um/drivers/ubd_kern.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
> index 13b1fe694b90..704989088f28 100644
> --- a/arch/um/drivers/ubd_kern.c
> +++ b/arch/um/drivers/ubd_kern.c
> @@ -371,15 +371,15 @@ static int ubd_setup_common(char *str, int *index_out, char **error_out)
>  
>  break_loop:
>  	file = strsep(&str, ",:");
> -	if (*file == '\0')
> +	if (file && *file == '\0')
>  		file = NULL;
>  
>  	backing_file = strsep(&str, ",:");
> -	if (*backing_file == '\0')
> +	if (backing_file && *backing_file == '\0')
>  		backing_file = NULL;
>  
>  	serial = strsep(&str, ",:");
> -	if (*serial == '\0')
> +	if (serial && *serial == '\0')
>  		serial = NULL;
>  
>  	if (backing_file && ubd_dev->no_cow) {

-- 
Gabriel Krisman Bertazi