linux-kernel - Re: [PATCH v6 04/12] drivers/infiniband: make setup_ctxt always get a nul terminated task comm

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Date:   Mon, 25 Oct 2021 14:16:29 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Yafang Shao <laoar.shao@...il.com>
Cc:     akpm@...ux-foundation.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, arnaldo.melo@...il.com,
        pmladek@...e.com, peterz@...radead.org, viro@...iv.linux.org.uk,
        valentin.schneider@....com, qiang.zhang@...driver.com,
        robdclark@...omium.org, christian@...uner.io,
        dietmar.eggemann@....com, mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, davem@...emloft.net, kuba@...nel.org,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org,
        dennis.dalessandro@...nelisnetworks.com,
        mike.marciniszyn@...nelisnetworks.com, dledford@...hat.com,
        jgg@...pe.ca, linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, oliver.sang@...el.com, lkp@...el.com,
        Andrii Nakryiko <andrii.nakryiko@...il.com>
Subject: Re: [PATCH v6 04/12] drivers/infiniband: make setup_ctxt always get
 a nul terminated task comm

On Mon, Oct 25, 2021 at 08:33:07AM +0000, Yafang Shao wrote:
> Use strscpy_pad() instead of strlcpy() to make the comm always nul
> terminated. As the comment above the hard-coded 16, we can replace it
> with TASK_COMM_LEN, then it will adopt to the comm size change.
> 
> Signed-off-by: Yafang Shao <laoar.shao@...il.com>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
> Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: Petr Mladek <pmladek@...e.com>
> ---
>  drivers/infiniband/hw/qib/qib.h          | 2 +-
>  drivers/infiniband/hw/qib/qib_file_ops.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/qib/qib.h b/drivers/infiniband/hw/qib/qib.h
> index 9363bccfc6e7..a8e1c30c370f 100644
> --- a/drivers/infiniband/hw/qib/qib.h
> +++ b/drivers/infiniband/hw/qib/qib.h
> @@ -196,7 +196,7 @@ struct qib_ctxtdata {
>  	pid_t pid;
>  	pid_t subpid[QLOGIC_IB_MAX_SUBCTXT];
>  	/* same size as task_struct .comm[], command that opened context */
> -	char comm[16];
> +	char comm[TASK_COMM_LEN];
>  	/* pkeys set by this use of this ctxt */
>  	u16 pkeys[4];
>  	/* so file ops can get at unit */
> diff --git a/drivers/infiniband/hw/qib/qib_file_ops.c b/drivers/infiniband/hw/qib/qib_file_ops.c
> index 63854f4b6524..7ab2b448c183 100644
> --- a/drivers/infiniband/hw/qib/qib_file_ops.c
> +++ b/drivers/infiniband/hw/qib/qib_file_ops.c
> @@ -1321,7 +1321,7 @@ static int setup_ctxt(struct qib_pportdata *ppd, int ctxt,
>  	rcd->tid_pg_list = ptmp;
>  	rcd->pid = current->pid;
>  	init_waitqueue_head(&dd->rcd[ctxt]->wait);
> -	strlcpy(rcd->comm, current->comm, sizeof(rcd->comm));
> +	strscpy_pad(rcd->comm, current->comm, sizeof(rcd->comm));

This should use (the adjusted) get_task_comm() instead of leaving this
open-coded.

>  	ctxt_fp(fp) = rcd;
>  	qib_stats.sps_ctxts++;
>  	dd->freectxts--;
> -- 
> 2.17.1
> 

-- 
Kees Cook