Re: [PATCH 1/2] liveupdate: fix GET_NAME ioctl argument validation

Hi,

> Cc: [email protected],  [email protected],  [email protected]

Please run ./scripts/get_maintainer.pl *.patch to get the full list of
people to Cc on the patch. You missed me and linux-kernel@.

On Wed, Jul 15 2026, Jackie Liu wrote:

> From: Jackie Liu <[email protected]>
>
> LIVEUPDATE_SESSION_GET_NAME was developed in the liveupdate/next branch
> while the session type validation change was carried in liveupdate-fixes.
> When the conflict between the two branches was resolved, the GET_NAME
> operation descriptor picked up the structure and last member from
> RETRIEVE_FD.
>
> This makes both its known size and minimum size 16 bytes rather than 72.
> Consequently, copy_struct_from_user() treats most of a normal GET_NAME
> argument as unknown trailing data and rejects it with -E2BIG when any of
> those bytes are nonzero. It also accepts a 16-byte argument and returns
> success after copying only a truncated session name.

Nit: The second line doesn't seem to be true. The get_session_name
selftest tries to create a session with 21 byte name and it passes. I
think it works because luo_session_get_name assumes ucmd->cmd is struct
liveupdate_session_get_name and so it tries to copy the whole thing via
luo_ucmd_respond(), and if the user buffer it large enough, it will
work.

But yeah, the -E2BIG seems like a real problem.

And anyway, that's a tricky bug and I missed it completely when I
reviewed the final rebased version. So thanks for fixing it.

Reviewed-by: Pratyush Yadav (Google) <[email protected]>

>
> Use the GET_NAME structure and its name field in the descriptor.
>
> Link: https://lore.kernel.org/all/[email protected]/
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: Jackie Liu <[email protected]>
> ---
>  kernel/liveupdate/luo_session.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/liveupdate/luo_session.c b/kernel/liveupdate/luo_session.c
> index b79b2a488974..f38b5b18f3f8 100644
> --- a/kernel/liveupdate/luo_session.c
> +++ b/kernel/liveupdate/luo_session.c
> @@ -378,7 +378,7 @@ static const struct luo_ioctl_op luo_session_ioctl_ops[] = {
>  	IOCTL_OP(LIVEUPDATE_SESSION_RETRIEVE_FD, luo_session_retrieve_fd,
>  		 struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_INCOMING),
>  	IOCTL_OP(LIVEUPDATE_SESSION_GET_NAME, luo_session_get_name,
> -		 struct liveupdate_session_retrieve_fd, token, LUO_IOCTL_ALL),
> +		 struct liveupdate_session_get_name, name, LUO_IOCTL_ALL),
>  };
>  
>  static bool luo_ioctl_type_valid(struct luo_session *session,

-- 
Regards,
Pratyush Yadav