linux-kernel - Re: [PATCH] Drop reference added by grab

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Date:   Thu, 5 Jan 2017 19:56:49 +0800
From:   Hanjun Guo <guohanjun@...wei.com>
To:     Zhou Chengming <zhouchengming1@...wei.com>,
        <linux-kernel@...r.kernel.org>, <viro@...iv.linux.org.uk>,
        <ebiederm@...ssion.com>, <balbi@...nel.org>
CC:     <konishi.ryusuke@....ntt.co.jp>, <jack@...e.cz>,
        <dmitry.torokhov@...il.com>, <caiqian@...hat.com>,
        <yangshukui@...wei.com>, <dingtianhong@...wei.com>,
        <lizefan@...wei.com>
Subject: Re: [PATCH] Drop reference added by grab_header

On 2017/1/5 19:33, Zhou Chengming wrote:
> Fixes CVE-2016-9191.

CVE-2016-9191 says that it's cgroup bug but turns out it's
not, I think you need to add more commit message to
explain it? For example, we got different calltrace stack
but all of them point to drop_sysctl_table() and it turns out
a reference count bug.

Thanks
Hanjun
>
> Reported-by: CAI Qian <caiqian@...hat.com>
> Tested-by: Yang Shukui <yangshukui@...wei.com>
> Signed-off-by: Zhou Chengming <zhouchengming1@...wei.com>
> ---
>  fs/proc/proc_sysctl.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
>
> diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
> index 5d931bf..c4c90bd 100644
> --- a/fs/proc/proc_sysctl.c
> +++ b/fs/proc/proc_sysctl.c
> @@ -718,7 +718,7 @@ static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
>  	ctl_dir = container_of(head, struct ctl_dir, header);
>  
>  	if (!dir_emit_dots(file, ctx))
> -		return 0;
> +		goto out;
>  
>  	pos = 2;
>  
> @@ -728,6 +728,7 @@ static int proc_sys_readdir(struct file *file, struct dir_context *ctx)
>  			break;
>  		}
>  	}
> +out:
>  	sysctl_head_finish(head);
>  	return 0;
>  }