linux-kernel - Re: [PATCH] eventfs: Test for dentries array allocated in eventfs

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Message-Id: <20231001001253.19971f4357e85d372ef34fc2@kernel.org>
Date:   Sun, 1 Oct 2023 00:12:53 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux trace kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH] eventfs: Test for dentries array allocated in
 eventfs_release()

On Sat, 30 Sep 2023 09:01:06 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> The dcache_dir_open_wrapper() could be called when a dynamic event is
> being deleted leaving a dentry with no children. In this case the
> dlist->dentries array will never be allocated. This needs to be checked
> for in eventfs_release(), otherwise it will trigger a NULL pointer
> dereference.

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thank you,

> 
> Fixes: ef36b4f92868 ("eventfs: Remember what dentries were created on dir open")
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  fs/tracefs/event_inode.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
> index 5f1714089884..8c8d64e76103 100644
> --- a/fs/tracefs/event_inode.c
> +++ b/fs/tracefs/event_inode.c
> @@ -421,7 +421,7 @@ static int eventfs_release(struct inode *inode, struct file *file)
>  	if (WARN_ON_ONCE(!dlist))
>  		return -EINVAL;
>  
> -	for (i = 0; dlist->dentries[i]; i++) {
> +	for (i = 0; dlist->dentries && dlist->dentries[i]; i++) {
>  		dput(dlist->dentries[i]);
>  	}
>  
> -- 
> 2.40.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>