Merge branch 'writable_limits' of git://decibel.fi.muni.cz/~xslaby/linux

* 'writable_limits' of git://decibel.fi.muni.cz/~xslaby/linux:
  unistd: add __NR_prlimit64 syscall numbers
  rlimits: implement prlimit64 syscall
  rlimits: switch more rlimit syscalls to do_prlimit
  rlimits: redo do_setrlimit to more generic do_prlimit
  rlimits: add rlimit64 structure
  rlimits: do security check under task_lock
  rlimits: allow setrlimit to non-current tasks
  rlimits: split sys_setrlimit
  rlimits: selinux, do rlimits changes under task_lock
  rlimits: make sure ->rlim_max never grows in sys_setrlimit
  rlimits: add task_struct to update_rlimit_cpu
  rlimits: security, add task_struct to setrlimit

Fix up various system call number conflicts.  We not only added fanotify
system calls in the meantime, but asm-generic/unistd.h added a wait4
along with a range of reserved per-architecture system calls.

3 files changed, 165 insertions, 62 deletions

diff --git a/kernel/compat.c b/kernel/compat.c
index 5adab05a3172..e167efce8423 100644
--- a/kernel/compat.c
+++ b/kernel/compat.c
@@ -279,11 +279,6 @@ asmlinkage long compat_sys_setrlimit(unsigned int resource,
                 struct compat_rlimit __user *rlim)
 {
         struct rlimit r;
-        int ret;
-        mm_segment_t old_fs = get_fs ();
-
-        if (resource >= RLIM_NLIMITS)
-                return -EINVAL;
 
         if (!access_ok(VERIFY_READ, rlim, sizeof(*rlim)) ||
             __get_user(r.rlim_cur, &rlim->rlim_cur) ||
@@ -294,10 +289,7 @@ asmlinkage long compat_sys_setrlimit(unsigned int resource,
                 r.rlim_cur = RLIM_INFINITY;
         if (r.rlim_max == COMPAT_RLIM_INFINITY)
                 r.rlim_max = RLIM_INFINITY;
-        set_fs(KERNEL_DS);
-        ret = sys_setrlimit(resource, (struct rlimit __user *) &r);
-        set_fs(old_fs);
-        return ret;
+        return do_prlimit(current, resource, &r, NULL);
 }
 
 #ifdef COMPAT_RLIM_OLD_INFINITY
@@ -329,16 +321,13 @@ asmlinkage long compat_sys_old_getrlimit(unsigned int resource,
 
 #endif
 
-asmlinkage long compat_sys_getrlimit (unsigned int resource,
+asmlinkage long compat_sys_getrlimit(unsigned int resource,
                 struct compat_rlimit __user *rlim)
 {
         struct rlimit r;
         int ret;
-        mm_segment_t old_fs = get_fs();
 
-        set_fs(KERNEL_DS);
-        ret = sys_getrlimit(resource, (struct rlimit __user *) &r);
-        set_fs(old_fs);
+        ret = do_prlimit(current, resource, NULL, &r);
         if (!ret) {
                 if (r.rlim_cur > COMPAT_RLIM_INFINITY)
                         r.rlim_cur = COMPAT_RLIM_INFINITY;
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index f66bdd33a6c6..6842eeba5879 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -16,13 +16,13 @@
  * siglock protection since other code may update expiration cache as
  * well.
  */
-void update_rlimit_cpu(unsigned long rlim_new)
+void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
 {
         cputime_t cputime = secs_to_cputime(rlim_new);
 
-        spin_lock_irq(&current->sighand->siglock);
-        set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
-        spin_unlock_irq(&current->sighand->siglock);
+        spin_lock_irq(&task->sighand->siglock);
+        set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
+        spin_unlock_irq(&task->sighand->siglock);
 }
 
 static int check_clock(const clockid_t which_clock)
diff --git a/kernel/sys.c b/kernel/sys.c
index e83ddbbaf89d..e9ad44489828 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1236,15 +1236,14 @@ SYSCALL_DEFINE2(setdomainname, char __user *, name, int, len)
 
 SYSCALL_DEFINE2(getrlimit, unsigned int, resource, struct rlimit __user *, rlim)
 {
-        if (resource >= RLIM_NLIMITS)
-                return -EINVAL;
-        else {
-                struct rlimit value;
-                task_lock(current->group_leader);
-                value = current->signal->rlim[resource];
-                task_unlock(current->group_leader);
-                return copy_to_user(rlim, &value, sizeof(*rlim)) ? -EFAULT : 0;
-        }
+        struct rlimit value;
+        int ret;
+
+        ret = do_prlimit(current, resource, NULL, &value);
+        if (!ret)
+                ret = copy_to_user(rlim, &value, sizeof(*rlim)) ? -EFAULT : 0;
+
+        return ret;
 }
 
 #ifdef __ARCH_WANT_SYS_OLD_GETRLIMIT
@@ -1272,44 +1271,89 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,
 
 #endif
 
-SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
+static inline bool rlim64_is_infinity(__u64 rlim64)
 {
-        struct rlimit new_rlim, *old_rlim;
-        int retval;
+#if BITS_PER_LONG < 64
+        return rlim64 >= ULONG_MAX;
+#else
+        return rlim64 == RLIM64_INFINITY;
+#endif
+}
+
+static void rlim_to_rlim64(const struct rlimit *rlim, struct rlimit64 *rlim64)
+{
+        if (rlim->rlim_cur == RLIM_INFINITY)
+                rlim64->rlim_cur = RLIM64_INFINITY;
+        else
+                rlim64->rlim_cur = rlim->rlim_cur;
+        if (rlim->rlim_max == RLIM_INFINITY)
+                rlim64->rlim_max = RLIM64_INFINITY;
+        else
+                rlim64->rlim_max = rlim->rlim_max;
+}
+
+static void rlim64_to_rlim(const struct rlimit64 *rlim64, struct rlimit *rlim)
+{
+        if (rlim64_is_infinity(rlim64->rlim_cur))
+                rlim->rlim_cur = RLIM_INFINITY;
+        else
+                rlim->rlim_cur = (unsigned long)rlim64->rlim_cur;
+        if (rlim64_is_infinity(rlim64->rlim_max))
+                rlim->rlim_max = RLIM_INFINITY;
+        else
+                rlim->rlim_max = (unsigned long)rlim64->rlim_max;
+}
+
+/* make sure you are allowed to change @tsk limits before calling this */
+int do_prlimit(struct task_struct *tsk, unsigned int resource,
+                struct rlimit *new_rlim, struct rlimit *old_rlim)
+{
+        struct rlimit *rlim;
+        int retval = 0;
 
         if (resource >= RLIM_NLIMITS)
                 return -EINVAL;
-        if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
-                return -EFAULT;
-        if (new_rlim.rlim_cur > new_rlim.rlim_max)
-                return -EINVAL;
-        old_rlim = current->signal->rlim + resource;
-        if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
-            !capable(CAP_SYS_RESOURCE))
-                return -EPERM;
-        if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
-                return -EPERM;
-
-        retval = security_task_setrlimit(resource, &new_rlim);
-        if (retval)
-                return retval;
-
-        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_cur > new_rlim->rlim_max)
+                        return -EINVAL;
+                if (resource == RLIMIT_NOFILE &&
+                                new_rlim->rlim_max > sysctl_nr_open)
+                        return -EPERM;
         }
 
-        task_lock(current->group_leader);
-        *old_rlim = new_rlim;
-        task_unlock(current->group_leader);
-
-        if (resource != RLIMIT_CPU)
+        /* protect tsk->signal and tsk->sighand from disappearing */
+        read_lock(&tasklist_lock);
+        if (!tsk->sighand) {
+                retval = -ESRCH;
                 goto out;
+        }
+
+        rlim = tsk->signal->rlim + resource;
+        task_lock(tsk->group_leader);
+        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;
+        }
+        task_unlock(tsk->group_leader);
 
         /*
          * RLIMIT_CPU handling.   Note that the kernel fails to return an error
@@ -1317,14 +1361,84 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
          * 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(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;
+}
+
+/* rcu lock must be held */
+static int check_prlimit_permission(struct task_struct *task)
+{
+        const struct cred *cred = current_cred(), *tcred;
+
+        tcred = __task_cred(task);
+        if ((cred->uid != tcred->euid ||
+             cred->uid != tcred->suid ||
+             cred->uid != tcred->uid  ||
+             cred->gid != tcred->egid ||
+             cred->gid != tcred->sgid ||
+             cred->gid != tcred->gid) &&
+             !capable(CAP_SYS_RESOURCE)) {
+                return -EPERM;
+        }
+
         return 0;
 }
 
+SYSCALL_DEFINE4(prlimit64, pid_t, pid, unsigned int, resource,
+                const struct rlimit64 __user *, new_rlim,
+                struct rlimit64 __user *, old_rlim)
+{
+        struct rlimit64 old64, new64;
+        struct rlimit old, new;
+        struct task_struct *tsk;
+        int ret;
+
+        if (new_rlim) {
+                if (copy_from_user(&new64, new_rlim, sizeof(new64)))
+                        return -EFAULT;
+                rlim64_to_rlim(&new64, &new);
+        }
+
+        rcu_read_lock();
+        tsk = pid ? find_task_by_vpid(pid) : current;
+        if (!tsk) {
+                rcu_read_unlock();
+                return -ESRCH;
+        }
+        ret = check_prlimit_permission(tsk);
+        if (ret) {
+                rcu_read_unlock();
+                return ret;
+        }
+        get_task_struct(tsk);
+        rcu_read_unlock();
+
+        ret = do_prlimit(tsk, resource, new_rlim ? &new : NULL,
+                        old_rlim ? &old : NULL);
+
+        if (!ret && old_rlim) {
+                rlim_to_rlim64(&old, &old64);
+                if (copy_to_user(old_rlim, &old64, sizeof(old64)))
+                        ret = -EFAULT;
+        }
+
+        put_task_struct(tsk);
+        return ret;
+}
+
+SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
+{
+        struct rlimit new_rlim;
+
+        if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
+                return -EFAULT;
+        return do_prlimit(current, resource, &new_rlim, NULL);
+}
+
 /*
  * It would make sense to put struct rusage in the task_struct,
  * except that would make the task_struct be *really big*.  After