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SubjectRe: [PATCH 2/3] extend get/setrlimit to support setting rlimits external to a process (v6)
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>


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 a990ace..9f357ab 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -702,11 +702,15 @@ 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 0e210a4..6ca9e7f 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1213,6 +1213,50 @@ 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

/*
@@ -1303,6 +1347,46 @@ 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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