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Subject[PATCH v3 24/27] core: implement getprlimit and setprlimit syscalls
Date
This patch adds the code to support the sys_setprlimit and set_getprlimit
syscalls which modify the rlim values of a selected process.

All rlim users now either use newly added accessors or doesn't need them
due to
- locking
- a process was just forked and nobody else knows about it yet (and
nobody can't thus read/write limits)

Based on Neil's work. Thank him.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Cc: James Morris <jmorris@namei.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
---
include/linux/syscalls.h | 4 ++
kernel/sys.c | 86 ++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 90 insertions(+), 0 deletions(-)
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index a990ace..6fd7ba6 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 c4065c5..626148f 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1212,6 +1212,61 @@ SYSCALL_DEFINE2(getrlimit, unsigned int, resource, struct rlimit __user *, rlim)
}
}

+static int check_prlimit_permission(struct task_struct *task)
+{
+ const struct cred *cred = current_cred(), *tcred;
+ int ret = 0;
+
+ rcu_read_lock();
+ 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)) {
+ ret = -EPERM;
+ }
+ rcu_read_unlock();
+ return ret;
+}
+
+SYSCALL_DEFINE3(getprlimit, pid_t, pid, unsigned int, resource,
+ struct rlimit __user *, rlim)
+{
+ struct rlimit val;
+ struct task_struct *tsk;
+ int ret;
+
+ if (resource >= RLIM_NLIMITS)
+ return -EINVAL;
+
+ read_lock(&tasklist_lock);
+
+ tsk = find_task_by_vpid(pid);
+ if (!tsk || !tsk->sighand) {
+ ret = -ESRCH;
+ goto err_unlock;
+ }
+
+ ret = check_prlimit_permission(tsk);
+ if (ret)
+ goto err_unlock;
+
+ task_lock(tsk->group_leader);
+ val = tsk->signal->rlim[resource];
+ task_unlock(tsk->group_leader);
+
+ read_unlock(&tasklist_lock);
+
+ return copy_to_user(rlim, &val, sizeof(*rlim)) ? -EFAULT : 0;
+err_unlock:
+ read_unlock(&tasklist_lock);
+ return ret;
+}
+
+
#ifdef __ARCH_WANT_SYS_OLD_GETRLIMIT

/*
@@ -1310,6 +1365,37 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
return do_setrlimit(current, resource, &new_rlim);
}

+SYSCALL_DEFINE3(setprlimit, pid_t, pid, unsigned int, resource,
+ struct rlimit __user *, rlim)
+{
+ struct task_struct *tsk;
+ struct rlimit new_rlim;
+ int ret;
+
+ if (resource >= RLIM_NLIMITS)
+ return -EINVAL;
+
+ if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
+ return -EFAULT;
+
+ rcu_read_lock();
+ tsk = find_task_by_vpid(pid);
+ if (!tsk) {
+ rcu_read_unlock();
+ return -ESRCH;
+ }
+ get_task_struct(tsk);
+ rcu_read_unlock();
+
+ ret = check_prlimit_permission(tsk);
+ if (!ret)
+ ret = do_setrlimit(tsk, resource, &new_rlim);
+
+ put_task_struct(tsk);
+
+ return ret;
+}
+
/*
* It would make sense to put struct rusage in the task_struct,
* except that would make the task_struct be *really big*. After
--
1.6.5.3


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