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    SubjectRe: [PATCH] getrusage sucks
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    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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