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SubjectRe: [PATCH] getrusage sucks
Date
On Saturday 12 November 2005 02:10, Chris Wright wrote:
> * dean gaudet (dean-list-linux-kernel@arctic.org) wrote:
> > do you have a use case for this new code?
>
> I'm with Dean. What problem are you trying to solve?

I just want to improve getrusage to account for the case in which a server
process needs to have usage information about client processes at run-time.
In this case RUSAGE_SELF is more important than RUSAGE_CHILDREN.
I think it would be an useful feature for some user-level applications.

At the beginning, I didn't want to propose any different prototype for the
function, even if I think that a more general (and correct) one would be

int getrusage(int who, struct rusage *usage, pid_t pid);

which accounts for all the situations we discussed so far.

However, I've added a more restrictive check (as asked by David) and the goto
proposed by Hua. Is now the patch right ? Do you think that it's useful ?

Many thanks,

Claudio


diff --git a/kernel/sys.c b/kernel/sys.c
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1746,9 +1746,29 @@ int getrusage(struct task_struct *p, int

asmlinkage long sys_getrusage(int who, struct rusage __user *ru)
{
- if (who != RUSAGE_SELF && who != RUSAGE_CHILDREN)
- return -EINVAL;
- return getrusage(current, who, ru);
+ struct rusage r;
+ struct task_struct* tsk = current;
+ read_lock(&tasklist_lock);
+ if ((who != RUSAGE_SELF) && (who != RUSAGE_CHILDREN)) {
+ tsk = find_task_by_pid(who);
+ if ((tsk == NULL) || (who <=0))
+ goto bad;
+ if (((current->uid != tsk->euid) ||
+ (current->uid != tsk->suid) ||
+ (current->uid != tsk->uid) ||
+ (current->gid != tsk->egid) ||
+ (current->gid != tsk->sgid) ||
+ (current->gid != tsk->gid)) && !capable(CAP_SYS_PTRACE))
+ goto bad;
+ who = RUSAGE_SELF;
+ }
+ k_getrusage(tsk, who, &r);
+ read_unlock(&tasklist_lock);
+ return copy_to_user(ru, &r, sizeof(r)) ? -EFAULT : 0;
+
+ bad:
+ read_unlock(&tasklist_lock);
+ return tsk ? -EPERM : -EINVAL;
}

asmlinkage long sys_umask(int mask)
-
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