rlimits: redo do_setrlimit to more generic do_prlimit

It now allows also reading of limits. I.e. all read and writes will
later use this function.

It takes two parameters, new and old limits which can be both NULL.
If new is non-NULL, the value in it is set to rlimits.
If old is non-NULL, current rlimits are stored there.
If both are non-NULL, old are stored prior to setting the new ones,
atomically.
(Similar to sigaction.)

Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/include/linux/resource.h b/include/linux/resource.h
index 037aa7e6335da2bb820dff8f4e58a4ba723d62fa..88d36f9145bacfa34ee6c32823413b09715e6ef2 100644 (file)
--- a/include/linux/resource.h
+++ b/include/linux/resource.h
@@ -80,8 +80,8 @@ struct rlimit64 {
 struct task_struct;
 
 int getrusage(struct task_struct *p, int who, struct rusage __user *ru);
-int do_setrlimit(struct task_struct *tsk, unsigned int resource,
-               struct rlimit *new_rlim);
+int do_prlimit(struct task_struct *tsk, unsigned int resource,
+               struct rlimit *new_rlim, struct rlimit *old_rlim);
 
 #endif /* __KERNEL__ */
 

diff --git a/kernel/sys.c b/kernel/sys.c
index c762eebdebf7bdae98506279ae535fac6dfead4d..bc7d1be0960e43f56975b34b85cae59529b75b96 100644 (file)
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1273,18 +1273,21 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
 #endif
 
 /* make sure you are allowed to change @tsk limits before calling this */
-int do_setrlimit(struct task_struct *tsk, unsigned int resource,
-               struct rlimit *new_rlim)
+int do_prlimit(struct task_struct *tsk, unsigned int resource,
+               struct rlimit *new_rlim, struct rlimit *old_rlim)
 {
-       struct rlimit *old_rlim;
+       struct rlimit *rlim;
        int retval = 0;
 
        if (resource >= RLIM_NLIMITS)
                return -EINVAL;
-       if (new_rlim->rlim_cur > new_rlim->rlim_max)
-               return -EINVAL;
-       if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open)
-               return -EPERM;
+       if (new_rlim) {
+               if (new_rlim->rlim_cur > new_rlim->rlim_max)
+                       return -EINVAL;
+               if (resource == RLIMIT_NOFILE &&
+                               new_rlim->rlim_max > sysctl_nr_open)
+                       return -EPERM;
+       }
 
        /* protect tsk->signal and tsk->sighand from disappearing */
        read_lock(&tasklist_lock);
@@ -1293,42 +1296,42 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
                goto out;
        }
 
-       old_rlim = tsk->signal->rlim + resource;
+       rlim = tsk->signal->rlim + resource;
        task_lock(tsk->group_leader);
-       if (new_rlim->rlim_max > old_rlim->rlim_max &&
-                       !capable(CAP_SYS_RESOURCE))
-               retval = -EPERM;
-       if (!retval)
-               retval = security_task_setrlimit(tsk->group_leader, resource,
-                               new_rlim);
-
-       if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
-               /*
-                * The caller is asking for an immediate RLIMIT_CPU
-                * expiry.  But we use the zero value to mean "it was
-                * never set".  So let's cheat and make it one second
-                * instead
-                */
-               new_rlim->rlim_cur = 1;
+       if (new_rlim) {
+               if (new_rlim->rlim_max > rlim->rlim_max &&
+                               !capable(CAP_SYS_RESOURCE))
+                       retval = -EPERM;
+               if (!retval)
+                       retval = security_task_setrlimit(tsk->group_leader,
+                                       resource, new_rlim);
+               if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
+                       /*
+                        * The caller is asking for an immediate RLIMIT_CPU
+                        * expiry.  But we use the zero value to mean "it was
+                        * never set".  So let's cheat and make it one second
+                        * instead
+                        */
+                       new_rlim->rlim_cur = 1;
+               }
+       }
+       if (!retval) {
+               if (old_rlim)
+                       *old_rlim = *rlim;
+               if (new_rlim)
+                       *rlim = *new_rlim;
        }
-
-       if (!retval)
-               *old_rlim = *new_rlim;
        task_unlock(tsk->group_leader);
 
-       if (retval || resource != RLIMIT_CPU)
-               goto out;
-
        /*
         * RLIMIT_CPU handling.   Note that the kernel fails to return an error
         * code if it rejected the user's attempt to set RLIMIT_CPU.  This is a
         * very long-standing error, and fixing it now risks breakage of
         * applications, so we live with it
         */
-       if (new_rlim->rlim_cur == RLIM_INFINITY)
-               goto out;
-
-       update_rlimit_cpu(tsk, new_rlim->rlim_cur);
+        if (!retval && new_rlim && resource == RLIMIT_CPU &&
+                        new_rlim->rlim_cur != RLIM_INFINITY)
+               update_rlimit_cpu(tsk, new_rlim->rlim_cur);
 out:
        read_unlock(&tasklist_lock);
        return retval;
@@ -1340,7 +1343,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
 
        if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
                return -EFAULT;
-       return do_setrlimit(current, resource, &new_rlim);
+       return do_prlimit(current, resource, &new_rlim, NULL);
 }
 
 /*