Re: [PATCH 2/3] extend get/setrlimit to support setting rlimits external to a process (v4)

["Américo Wang" <xiyou.wangcong@gmail.com>]

On Sun, Oct 04, 2009 at 08:54:05PM -0400, Neil Horman wrote:
>Add syscall infrastructure for getprlimit/setprlimit
>
>This patch adds the definitions for the get/setprlimit syscalls.  They are
>identical to the get/setlimit calls, except that they allow the caller to
>manipulate limits for processes other than themselves.
>
>Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

Hello, Neil.

What is your point of adding two new syscalls?
Why not add them to prctl(2)? :-)


Thanks.

>
>
> include/linux/syscalls.h |    4 ++
> kernel/sys.c             |   84 +++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 88 insertions(+)
>
>diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
>index 80de700..535210a 100644
>--- a/include/linux/syscalls.h
>+++ b/include/linux/syscalls.h
>@@ -584,11 +584,15 @@ asmlinkage long sys_newuname(struct new_utsname __user *name);
> 
> asmlinkage long sys_getrlimit(unsigned int resource,
> 				struct rlimit __user *rlim);
>+asmlinkage long sys_getprlimit(pid_t pid, unsigned int resource,
>+				struct rlimit __user *rlim);
> #if defined(COMPAT_RLIM_OLD_INFINITY) || !(defined(CONFIG_IA64))
> asmlinkage long sys_old_getrlimit(unsigned int resource, struct rlimit __user *rlim);
> #endif
> asmlinkage long sys_setrlimit(unsigned int resource,
> 				struct rlimit __user *rlim);
>+asmlinkage long	sys_setprlimit(pid_t pid, unsigned int resource,
>+				struct rlimit __user *rlim);
> asmlinkage long sys_getrusage(int who, struct rusage __user *ru);
> asmlinkage long sys_umask(int mask);
> 
>diff --git a/kernel/sys.c b/kernel/sys.c
>index 05bd22a..4fe1140 100644
>--- a/kernel/sys.c
>+++ b/kernel/sys.c
>@@ -1211,6 +1211,50 @@ SYSCALL_DEFINE2(getrlimit, unsigned int, resource, struct rlimit __user *, rlim)
> 	}
> }
> 
>+SYSCALL_DEFINE3(getprlimit, pid_t, pid, unsigned int, resource,
>+		struct rlimit __user *, rlim)
>+{
>+	unsigned long flags;
>+	struct task_struct *tsk;
>+	struct pid *ppid;
>+	int retval = -EINVAL;
>+
>+	ppid = find_get_pid(pid);
>+	if (!ppid)
>+		goto out;
>+
>+	tsk = get_pid_task(ppid, PIDTYPE_PID);
>+
>+	if (!tsk)
>+		goto out_put_pid;
>+
>+	if (resource >= RLIM_NLIMITS)
>+		goto out_put_all;
>+
>+	retval = -EBUSY;
>+	if (!lock_task_sighand(tsk, &flags))
>+		goto out_put_all;
>+
>+	else {
>+		struct rlimit val;
>+
>+		task_lock(tsk->group_leader);
>+		val = current->signal->rlim[resource];
>+		task_unlock(tsk->group_leader);
>+		retval = copy_to_user(rlim, &val, sizeof(*rlim)) ? -EFAULT : 0;
>+	}
>+
>+	unlock_task_sighand(tsk, &flags);
>+
>+out_put_all:
>+	put_task_struct(tsk);
>+out_put_pid:
>+	put_pid(ppid);
>+out:
>+	return retval;
>+}
>+
>+
> #ifdef __ARCH_WANT_SYS_OLD_GETRLIMIT
> 
> /*
>@@ -1301,6 +1345,46 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
> 	return do_setrlimit(resource, &new_rlim, current);
> }
> 
>+SYSCALL_DEFINE3(setprlimit, pid_t, pid, unsigned int, resource,
>+		struct rlimit __user *, rlim)
>+{
>+	struct task_struct *tsk;
>+	struct pid *ppid;
>+	unsigned long flags;
>+	struct rlimit new_rlim;
>+	int retval = -EINVAL;
>+
>+	ppid = find_get_pid(pid);
>+	if (!ppid)
>+		goto out;
>+
>+	tsk = get_pid_task(ppid, PIDTYPE_PID);
>+
>+	if (!tsk)
>+		goto out_put_pid;
>+
>+	if (resource >= RLIM_NLIMITS)
>+		goto out_put_all;
>+
>+	retval = -EFAULT;
>+	if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
>+		goto out_put_all;
>+
>+	if (!lock_task_sighand(tsk, &flags))
>+		goto out_put_all;
>+
>+	retval = do_setrlimit(resource, &new_rlim, tsk);
>+
>+	unlock_task_sighand(tsk, &flags);
>+
>+out_put_all:
>+	put_task_struct(tsk);
>+out_put_pid:
>+	put_pid(ppid);
>+out:
>+	return retval;
>+}
>+
> /*
>  * It would make sense to put struct rusage in the task_struct,
>  * except that would make the task_struct be *really big*.  After
>--
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