[RFC] [PATCH] capset returns -EPERM when pid==current->pid

[RFC] [PATCH] capset returns -EPERM when pid==current->pid

[Serge E. Hallyn]

In the current kernel/capability.c:sys_capset() code, permission is
denied if CAP_SETPCAP is not held and pid is positive.  pid=0 means use
the current process, and this is allowed.  But using the current
process' pid is not allowed.  The man page for capsetp simply says that
CAP_SETPCAP is required to use this function, and does not mention the
exception for pid=0.  

The current behavior seems inconsistent.  The attached patch also
allows a process to call capset() on itself.  Does this seem reasonable?

thanks,
-serge

Index: linux-2.6.10-mm1/kernel/capability.c
===================================================================
--- linux-2.6.10-mm1.orig/kernel/capability.c	2005-01-04 11:51:21.000000000 -0600
+++ linux-2.6.10-mm1/kernel/capability.c	2005-01-04 11:52:58.000000000 -0600
@@ -147,7 +147,7 @@ asmlinkage long sys_capset(cap_user_head
      if (get_user(pid, &header->pid))
 	     return -EFAULT; 
 
-     if (pid && !capable(CAP_SETPCAP))
+     if (pid && pid != current->pid && !capable(CAP_SETPCAP))
              return -EPERM;
 
      if (copy_from_user(&effective, &data->effective, sizeof(effective)) ||

Re: [RFC] [PATCH] capset returns -EPERM when pid==current->pid

[Chris Wright]

* Serge E. Hallyn (serue@us.ibm.com) wrote:
> In the current kernel/capability.c:sys_capset() code, permission is
> denied if CAP_SETPCAP is not held and pid is positive.  pid=0 means use
> the current process, and this is allowed.  But using the current
> process' pid is not allowed.  The man page for capsetp simply says that
> CAP_SETPCAP is required to use this function, and does not mention the
> exception for pid=0.  
> 
> The current behavior seems inconsistent.  The attached patch also
> allows a process to call capset() on itself.  Does this seem reasonable?

Yes.

From: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>

Index: linux-2.6.10-mm1/kernel/capability.c
===================================================================
--- linux-2.6.10-mm1.orig/kernel/capability.c	2005-01-04 11:51:21.000000000 -0600
+++ linux-2.6.10-mm1/kernel/capability.c	2005-01-04 11:52:58.000000000 -0600
@@ -147,7 +147,7 @@ asmlinkage long sys_capset(cap_user_head
      if (get_user(pid, &header->pid))
 	     return -EFAULT; 
 
-     if (pid && !capable(CAP_SETPCAP))
+     if (pid && pid != current->pid && !capable(CAP_SETPCAP))
              return -EPERM;
 
      if (copy_from_user(&effective, &data->effective, sizeof(effective)) ||