Re: setgroups hook

Previous message: Antony Edwards: "setgroups hook"
In reply to: Antony Edwards: "setgroups hook"
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chrisat_private

* Antony Edwards (aedwardat_private) wrote:
> 
> Hi,
> 
> The setgroups16 system call (in kernel/uid16.c) is not protected by the
> task_ops->setgroups
> hook. Unfortunately, adding this hook isn't completely straightforward. The
> problem is that
> the group list in setgroups16 is 16-bit, while the task_ops->setgroups hook
> expects 32-bit
> gid's. There seem to be two reasonable solutions:
> 
> (1) Add a parameter to the setgroups hook to give the list format.
> 
> (2) Change the existing code to convert the array to 32-bit gid's and call
> the
>      normal setgroups function.
> 
> Just wanted to get peoples thoughts before I wrote a patch.

Ah, another good catch ;-)  Keeping the interface simple is important; I
prefer the second option.  Something like:

===== kernel/uid16.c 1.1 vs edited =====

--- 1.1/kernel/uid16.c	Thu Feb 15 13:25:47 2001
+++ edited/kernel/uid16.c	Sat Feb  2 19:26:31 2002
@@ -12,6 +12,7 @@
 #include <linux/prctl.h>
 #include <linux/init.h>
 #include <linux/highuid.h>
+#include <linux/security.h>
 
 #include <asm/uaccess.h>
 
@@ -128,6 +129,7 @@
 asmlinkage long sys_setgroups16(int gidsetsize, old_gid_t *grouplist)
 {
 	old_gid_t groups[NGROUPS];
+	gid_t new_groups[NGROUPS];
 	int i;
 
 	if (!capable(CAP_SETGID))
@@ -137,7 +139,11 @@
 	if (copy_from_user(groups, grouplist, gidsetsize * sizeof(old_gid_t)))
 		return -EFAULT;
 	for (i = 0 ; i < gidsetsize ; i++)
-		current->groups[i] = (gid_t)groups[i];
+		new_groups[i] = (gid_t)groups[i];
+	i = security_ops->task_ops->setgroups(gidsetsize, new_groups);
+	if (i)
+		return i;
+	memcpy(current->groups, new_groups, gidsetsize * sizeof(gid_t));
 	current->ngroups = gidsetsize;
 	return 0;
 }

thanks,
-chris
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