On Fri, Dec 13, 2013 at 9:23 AM, Stephen Smalley <sds@xxxxxxxxxxxxx> wrote:
> On 12/02/2013 04:10 PM, William Roberts wrote:
>> Re-factor proc_pid_cmdline() to use get_cmdline_length() and
>> copy_cmdline() helpers from mm.h
>>
>> Signed-off-by: William Roberts <wroberts@xxxxxxxxxx>
>> ---
>> fs/proc/base.c | 35 ++++++++++-------------------------
>> 1 file changed, 10 insertions(+), 25 deletions(-)
>>
>> diff --git a/fs/proc/base.c b/fs/proc/base.c
>> index 03c8d74..fb4eda5 100644
>> --- a/fs/proc/base.c
>> +++ b/fs/proc/base.c
>> @@ -203,37 +203,22 @@ static int proc_root_link(struct dentry *dentry, struct path *path)
>> static int proc_pid_cmdline(struct task_struct *task, char * buffer)
>> {
>> int res = 0;
>> - unsigned int len;
>> + unsigned int len = 0;
>
> Why? You set len below before first use, so this is redundant.
>
Yep you're right.
>> struct mm_struct *mm = get_task_mm(task);
>> if (!mm)
>> - goto out;
>> - if (!mm->arg_end)
>> - goto out_mm; /* Shh! No looking before we're done */
>> + return 0;
>
> Equivalent to goto out in the original code, so why change it? Don't
> make unnecessary changes.
>
> Also, I think the get_task_mm() ought to move into the helper (or all of
> proc_pid_cmdline() should just become the helper). In what situation
> will you not be calling get_task_mm() and mmput() around every call to
> the helper?
Again my thought on this is to reduce get_task_mm() and mmput() calls.
How expensive are they, etc. However, just to recap the other email. If we
move to saying the audit cache of this can be capped at PATH_MAX even
if it results in some wasted memory, we can just take the original procfs code
and add a length argument.
>
>>
>> - len = mm->arg_end - mm->arg_start;
>> -
>> + len = get_cmdline_length(mm);
>> + if (!len)
>> + goto mm_out;
>
> Could be moved into the helper. Not sure how the inline function helps
> readability or maintainability.
Sure... mostly for readability.
>
>> +
>> + /*The caller of this allocates a page */
>> if (len > PAGE_SIZE)
>> len = PAGE_SIZE;
>
> If the capping of len is handled by the caller, then pass an int to your
> helper rather than an unsigned int to avoid problems later with
> access_process_vm().
Ok... just weird that lengths are signed to me. when will you ever have negative
space?
>
>> -out_mm:
>> +
>> + res = copy_cmdline(task, mm, buffer, len);
>> +mm_out:
>> mmput(mm);
>
> Odd style. If there is only one exit path, just call it out; if there
> are two, keep them as out_mm and out.
>
Yes their is only 1 jmp label. Your right, this is odd.
>> -out:
>> return res;
>> }
>>
>>
>
--
Respectfully,
William C Roberts
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