Re: [PATCH v2 RESEND] kobject: fix out-of-bounds access in kobject_action_type()

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Aug 25, 2026 at 03:05:25PM +0800, Jiacheng Xu wrote:
> kobject_action_type() uses the position of the first space in the input
> as the length of the uevent action. It then checks the byte at that
> position in the corresponding action string.
> 
> An embedded NUL byte can make strncmp() report a match while
> count_first is already greater than the actual length of the action
> string. For example, the input "bind\0 ..." makes the parser access
> kobject_actions[KOBJ_BIND][5], which is beyond the end of the "bind"
> string.
> 
> Use strlen() to verify that the input action length exactly matches the
> known action string before accepting the match. This avoids indexing
> the action string with an out-of-bounds offset.
> 
> Fixes: f36776fafbaa ("kobject: support passing in variables for synthetic uevents")
> Signed-off-by: Jiacheng Xu <stitch@zju.edu.cn>
> ---
>  lib/kobject_uevent.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/lib/kobject_uevent.c b/lib/kobject_uevent.c
> index ddbc4d7482d2..b03562301bfe 100644
> --- a/lib/kobject_uevent.c
> +++ b/lib/kobject_uevent.c
> @@ -83,7 +83,7 @@ static int kobject_action_type(const char *buf, size_t count,
>  	for (action = 0; action < ARRAY_SIZE(kobject_actions); action++) {
>  		if (strncmp(kobject_actions[action], buf, count_first) != 0)
>  			continue;
> -		if (kobject_actions[action][count_first] != '\0')
> +		if (strlen(kobject_actions[action]) != count_first)
>  			continue;
>  		if (args)
>  			*args = args_start;
> -- 
> 2.51.0
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- This looks like a new version of a previously submitted patch, but you
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  Please read the section entitled "The canonical patch format" in the
  kernel file, Documentation/process/submitting-patches.rst for what
  needs to be done here to properly describe this.

If you wish to discuss this problem further, or you have questions about
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thanks,

greg k-h's patch email bot