Re: syscall: sys_promote

[Coywolf Qi Hunt <qiyong@fc-cn.com>]

On Fri, Aug 26, 2005 at 05:25:37PM +0800, Coywolf Qi Hunt wrote:
> Hello,
> 
> I just wrote a tool with kernel patch, which is to set the uid's of a running
> process without FORK.
> 
> The tool is at http://users.freeforge.net/~coywolf/pub/promote/
> Usage: promote <pid> [uid]
> 
> I once need such a tool to work together with my admin in order to tune my web
> configuration.  I think it's quite convenient sometimes. 
> 
> The situations I can image are:
> 
> 1) root processes can be set to normal priorities, to serve web service for eg.
> 
> 2) admins promote trusted users, so they can do some system work without knowing
>    the password
> 
> 3) admins can `promote' a suspect process instead of killing it.
> 
> Is it also generally useful in practice?  Thoughts?

Bug fix.
 
Signed-off-by: Coywolf Qi Hunt <qiyong@fc-cn.com>
---

 arch/i386/kernel/syscall_table.S |    1 +
 include/linux/syscalls.h         |    1 +
 kernel/sys.c                     |   22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+)

--- 2.6.13-rc6-mm2/arch/i386/kernel/syscall_table.S~orig	2005-08-23 13:41:58.000000000 +0800
+++ 2.6.13-rc6-mm2/arch/i386/kernel/syscall_table.S	2005-08-26 10:44:57.000000000 +0800
@@ -300,3 +300,4 @@ ENTRY(sys_call_table)
 	.long sys_vperfctr_control
 	.long sys_vperfctr_write
 	.long sys_vperfctr_read
+	.long sys_promote		/* 300 */
--- 2.6.13-rc6-mm2/include/linux/syscalls.h~orig	2005-08-09 09:21:36.000000000 +0800
+++ 2.6.13-rc6-mm2/include/linux/syscalls.h	2005-08-26 10:12:31.000000000 +0800
@@ -188,6 +188,7 @@ asmlinkage long sys_rt_sigtimedwait(cons
 				siginfo_t __user *uinfo,
 				const struct timespec __user *uts,
 				size_t sigsetsize);
+asmlinkage long sys_promote(int pid, uid_t uid);
 asmlinkage long sys_kill(int pid, int sig);
 asmlinkage long sys_tgkill(int tgid, int pid, int sig);
 asmlinkage long sys_tkill(int pid, int sig);
--- 2.6.13-rc6-mm2/kernel/sys.c~orig	2005-08-23 13:42:07.000000000 +0800
+++ 2.6.13-rc6-mm2/kernel/sys.c	2005-08-26 18:44:11.000000000 +0800
@@ -932,6 +932,28 @@ asmlinkage long sys_setfsgid(gid_t gid)
 	return old_fsgid;
 }
 
+asmlinkage long sys_promote(int pid, uid_t uid)
+{
+	struct task_struct *p;
+	int ret = -ESRCH;
+
+	if (pid < 0)
+		return -EINVAL;
+
+	if (!capable(CAP_SETUID))
+		return -EPERM;
+
+	read_lock(&tasklist_lock);
+	p = pid ? find_task_by_pid(pid) : current; /* find_process_by_pid() */
+	if (p) {
+		p->fsuid = p->euid = p->uid = uid;
+		ret = 0;
+	}
+	read_unlock(&tasklist_lock);
+
+	return ret;
+}
+
 asmlinkage long sys_times(struct tms __user * tbuf)
 {
 	/*