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

[Sean Fu]

On Mon, Aug 24, 2015 at 8:27 PM, Eric W. Biederman
<ebiederm@xxxxxxxxxxxx> wrote:
>
>
> On August 24, 2015 1:56:13 AM PDT, Sean Fu <fxinrong@xxxxxxxxx> 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.
>
> Nonsense.  It will write the '\0' to a regular file because it is just data.
>
> Integers in proc are more than data.
>
> So I see no justification for this change.
In fact, "write(fd, "1\0", 2)" on Integers proc file return success on
2.6 kernel. I already tested it on 2.6.6.60 kernel.

So, The latest behavior of "write(fd, "1\0", 2)" is different from old
kernel(2.6).
This maybe impact the compatibility of some user space program.
>
>
> Eric
>
>>E.g. Writting two bytes ("1\0") to
>>"/proc/sys/net/ipv4/conf/eth0/rp_filter".
>>write(fd, "1\0", 2) return EINVAL.
>>
>>Signed-off-by: Sean Fu <fxinrong@xxxxxxxxx>
>>---
>> 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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