linux-kernel - Re: [PATCH] kernel/sysctl.c: If "count" including the terminating byte '\0' the write system call should retrun success.

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Date:	Tue, 25 Aug 2015 22:39:57 +0200
From:	Heinrich Schuchardt <xypron.glpk@....de>
To:	Sean Fu <fxinrong@...il.com>,
	Andrey Ryabinin <ryabinin.a.a@...il.com>,
	Ulrich Obergfell <uobergfe@...hat.com>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Prarit Bhargava <prarit@...hat.com>,
	Eric B Munson <emunson@...mai.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Don Zickus <dzickus@...hat.com>,
	David Rientjes <rientjes@...gle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/sysctl.c: If "count" including the terminating
 byte '\0' the write system call should retrun success.



On 24.08.2015 10:56, Sean Fu wrote:
> when the input argument "count" including the terminating byte "\0",
> The write system call return EINVAL on proc file.
> But it return success on regular file.
> 
> E.g. Writting two bytes ("1\0") to "/proc/sys/net/ipv4/conf/eth0/rp_filter".
> write(fd, "1\0", 2) return EINVAL.

Reading through kernel/sysctl.c it looks like you are allowing
"1\01" to be used to pass two integers or two longs.
This is not what you describe as target of your patch.

Parameter tr returned from proc_get_long should be checked in
__do_proc_dointvec,
__do_proc_doulongvec_minmax.

Best regards

Heinrich Schuchardt

> 
> Signed-off-by: Sean Fu <fxinrong@...il.com>
> ---
>  kernel/sysctl.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 19b62b5..c2b0594 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -2004,7 +2004,7 @@ static int do_proc_dointvec_conv(bool *negp,
> unsigned long *lvalp,
>         return 0;
>  }
> 
> -static const char proc_wspace_sep[] = { ' ', '\t', '\n' };
> +static const char proc_wspace_sep[] = { ' ', '\t', '\n', '\0' };
> 
>  static int __do_proc_dointvec(void *tbl_data, struct ctl_table *table,
>                   int write, void __user *buffer,
> 
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