linux-kernel - Re: [PATCH] kernel: profile: fix error return code of create_proc

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Date:   Tue, 9 Mar 2021 10:32:57 +0100
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Jia-Ju Bai <baijiaju1990@...il.com>
Cc:     linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] kernel: profile: fix error return code of
 create_proc_profile()

On 2021-03-09 01:02:15 [-0800], Jia-Ju Bai wrote:
> When proc_create() returns NULL to entry, no error return code of
> create_proc_profile() is assigned.
> To fix this bug, err is assigned with -ENOMEM in this case.

I preserved what was in commit
    c270a817196a9 ("profile: Fix CPU hotplug callback registration")

which was already in commit
    c33fff0afbef4 ("kernel: use non-racy method for proc entries creation")

and goes back to its original introduction in history tree's commit
    423284ee6eb52 ("[PATCH] consolidate prof_cpu_mask")

which is ignoring a failure here.
If we decide otherwise and not ignore the error then it would be good to
use an earlier commit so the change also makes into v4.4+ stable.

> Fixes: e722d8daafb9 ("profile: Convert to hotplug state machine")
> Reported-by: TOTE Robot <oslab@...nghua.edu.cn>
> Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
> ---
>  kernel/profile.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/profile.c b/kernel/profile.c
> index 6f69a4195d56..65bf03bb8a5e 100644
> --- a/kernel/profile.c
> +++ b/kernel/profile.c
> @@ -549,8 +549,10 @@ int __ref create_proc_profile(void)
>  #endif
>  	entry = proc_create("profile", S_IWUSR | S_IRUGO,
>  			    NULL, &profile_proc_ops);
> -	if (!entry)
> +	if (!entry) {
> +		err = -ENOMEM;
>  		goto err_state_onl;
> +	}
>  	proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
>  
>  	return err;

Sebastian