[PATCH] Re: Local root exploit with kmod and modutils > 2.1.121

[PATCH] Re: Local root exploit with kmod and modutils > 2.1.121

[Xavier Bestel]

Hi,

as modprobe (insmod) seems to have POSIX args handling, we should perhaps add "--"
to the modprobe cmdline, in order to stop further args processing, and to avoid
mixing a textual argument with an option.
BTW, it should perhaps be generalized.

Xav


--- linux-2.4-test10/kernel/kmod.c	Tue Sep 26 01:18:55 2000
+++ linux/kernel/kmod.c	Thu Nov 16 19:57:45 2000
@@ -133,7 +133,7 @@
 static int exec_modprobe(void * module_name)
 {
 	static char * envp[] = { "HOME=/", "TERM=linux", "PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL };
-	char *argv[] = { modprobe_path, "-s", "-k", (char*)module_name, NULL };
+	char *argv[] = { modprobe_path, "-s", "-k", "--", (char*)module_name, NULL };
 	int ret;
 
 	ret = exec_usermodehelper(modprobe_path, argv, envp);


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[PATCH] Re: Local root exploit with kmod and modutils > 2.1.121

[Xavier Bestel]

Hi,

as modprobe (insmod) args parsing seems POSIX compliant, we should put a
"--" before
what should be interpreted only as a textual argument, not as an option.
This is a lot safer: whatever is passed, modprobe will take it as a module
name.

--- linux-2.4.0-test10/kernel/kmod.c    Tue Sep 26 01:18:55 2000
+++ linux/kernel/kmod.c Thu Nov 16 19:57:45 2000
@@ -133,7 +133,7 @@
 static int exec_modprobe(void * module_name)
 {
        static char * envp[] = { "HOME=/", "TERM=linux",
"PATH=/sbin:/usr/sbin:/bin:/usr/bin", NULL };
-       char *argv[] = { modprobe_path, "-s", "-k", (char*)module_name,
NULL };
+       char *argv[] = { modprobe_path, "-s", "-k", "--",
(char*)module_name, NULL };
        int ret;

        ret = exec_usermodehelper(modprobe_path, argv, envp);
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Re: [PATCH] Re: Local root exploit with kmod and modutils > 2.1.121

[Keith Owens]

On Thu, 16 Nov 2000 22:21:52 +0100, 
Xavier Bestel <xavier.bestel@free.fr> wrote:
>as modprobe (insmod) args parsing seems POSIX compliant, we should put a
>"--" before
>what should be interpreted only as a textual argument, not as an option.
>This is a lot safer: whatever is passed, modprobe will take it as a module
>name.

That only solves one of the two exploit methods.  modutils 2.3.20
solves both without any kernel changes, mainly so it fixes the problem
on all kernels, including 2.2.

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Re: [PATCH] Re: Local root exploit with kmod and modutils > 2.1.121

[H. Peter Anvin]

Followup to:  <5529.974412016@ocs3.ocs-net>
By author:    Keith Owens <kaos@ocs.com.au>
In newsgroup: linux.dev.kernel
>
> On Thu, 16 Nov 2000 22:21:52 +0100, 
> Xavier Bestel <xavier.bestel@free.fr> wrote:
> >as modprobe (insmod) args parsing seems POSIX compliant, we should put a
> >"--" before
> >what should be interpreted only as a textual argument, not as an option.
> >This is a lot safer: whatever is passed, modprobe will take it as a module
> >name.
> 
> That only solves one of the two exploit methods.  modutils 2.3.20
> solves both without any kernel changes, mainly so it fixes the problem
> on all kernels, including 2.2.
> 

However, the kernel change is probably still a good idea.

	-hpa
-- 
<hpa@transmeta.com> at work, <hpa@zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."
http://www.zytor.com/~hpa/puzzle.txt
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