[PATCH] libmount: avoid endless loop in, mnt_get_kernel_cmdline_option

[PATCH] libmount: avoid endless loop in, mnt_get_kernel_cmdline_option

[Bernhard Voelker]

>From 4ddf21607847570e1da3b692276f2a8242bd5af6 Mon Sep 17 00:00:00 2001
From: Bernhard Voelker <mail@bernhard-voelker.de>
Date: Fri, 30 Nov 2012 17:12:12 +0100
Subject: [PATCH] libmount: avoid endless loop in
 mnt_get_kernel_cmdline_option

The above function infloops when the name to search for can only
be found at the beginning of /proc/cmdline but doesn't match,
e.g. when searching for "ro" in "root=/dev/sda1 quiet vga=0x31a".

* libmount/src/utils.c (mnt_get_kernel_cmdline_option): Replace
while by for loop to ensure the pointer p is incremented.

Signed-off-by: Bernhard Voelker <mail@bernhard-voelker.de>
---
 libmount/src/utils.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/libmount/src/utils.c b/libmount/src/utils.c
index 74c3ad5..be242d0 100644
--- a/libmount/src/utils.c
+++ b/libmount/src/utils.c
@@ -947,9 +947,7 @@ char *mnt_get_kernel_cmdline_option(const char *name)
 	if (len && *(name + len - 1) == '=')
 		val = 1;

-	while (p && *p) {
-		if (p != buf)
-			p++;
+	for ( ; p && *p; p++) {
 		if (!(p = strstr(p, name)))
 			break;			/* not found the option */
 		if (p != buf && !isblank(*(p - 1)))
-- 
1.7.7

Re: [PATCH] libmount: avoid endless loop in, mnt_get_kernel_cmdline_option

[Bernhard Voelker]

On 11/30/2012 05:14 PM, Bernhard Voelker wrote:
> From 4ddf21607847570e1da3b692276f2a8242bd5af6 Mon Sep 17 00:00:00 2001
> From: Bernhard Voelker <mail@bernhard-voelker.de>
> Date: Fri, 30 Nov 2012 17:12:12 +0100
> Subject: [PATCH] libmount: avoid endless loop in
>  mnt_get_kernel_cmdline_option

Hi Karel,

BTW: the #ifdef in mnt_get_kernel_cmdline_option doesn't seem
to work to make use of the LIBMOUNT_KERNEL_CMDLINE env var:

--- tests/expected/libmount/utils-kernel-cmdline       2012-11-22 10:41:18.424077009 +0100
+++ tests/output/libmount/utils-kernel-cmdline   2012-12-04 16:17:49.629199061 +0100
@@ -1,5 +1,5 @@
-'selinux=' found, argument: '0'
+'selinux=' not found
 'selinux' not found
-'ro' found
+'ro' not found
 'ro=' not found
-'root=' found, argument: 'UUID=33230ae2-1093-4353-824c-f7ca09a2a882'
+'root=' found, argument: '/dev/sda1'

And ltraced:

 $ export LIBMOUNT_KERNEL_CMDLINE=`pwd`/tests/ts/libmount/files/kernel_cmdline
 $ ltrace -e getenv,fopen -f ./test_mount_utils  --kernel-cmdline selinux=
 getenv("LIBMOUNT_DEBUG")                                                                    = NULL
 fopen("/proc/cmdline", "r")                                                                 = 0x609010
 'selinux=' not found
 +++ exited (status 0) +++

I.e. the utils test may only work on your PC. ;-)


BTW2: the libmount tests all fail when the user has set
LIBMOUNT_DEBUG=0xffff, because the produced output differs.
Maybe LIBMOUNT_DEBUG should be unset in tests/run.sh?

Have a nice day,
Berny

Re: [PATCH] libmount: avoid endless loop in, mnt_get_kernel_cmdline_option

[Karel Zak]

On Tue, Dec 04, 2012 at 04:22:02PM +0100, Bernhard Voelker wrote:
> On 11/30/2012 05:14 PM, Bernhard Voelker wrote:
> > From 4ddf21607847570e1da3b692276f2a8242bd5af6 Mon Sep 17 00:00:00 2001
> > From: Bernhard Voelker <mail@bernhard-voelker.de>
> > Date: Fri, 30 Nov 2012 17:12:12 +0100
> > Subject: [PATCH] libmount: avoid endless loop in
> >  mnt_get_kernel_cmdline_option
> 
> Hi Karel,
> 
> BTW: the #ifdef in mnt_get_kernel_cmdline_option doesn't seem
> to work to make use of the LIBMOUNT_KERNEL_CMDLINE env var:
> 
> --- tests/expected/libmount/utils-kernel-cmdline       2012-11-22 10:41:18.424077009 +0100
> +++ tests/output/libmount/utils-kernel-cmdline   2012-12-04 16:17:49.629199061 +0100
> @@ -1,5 +1,5 @@
> -'selinux=' found, argument: '0'
> +'selinux=' not found
>  'selinux' not found
> -'ro' found
> +'ro' not found
>  'ro=' not found
> -'root=' found, argument: 'UUID=33230ae2-1093-4353-824c-f7ca09a2a882'
> +'root=' found, argument: '/dev/sda1'
> 
> And ltraced:
> 
>  $ export LIBMOUNT_KERNEL_CMDLINE=`pwd`/tests/ts/libmount/files/kernel_cmdline
>  $ ltrace -e getenv,fopen -f ./test_mount_utils  --kernel-cmdline selinux=
>  getenv("LIBMOUNT_DEBUG")                                                                    = NULL
>  fopen("/proc/cmdline", "r")                                                                 = 0x609010
>  'selinux=' not found
>  +++ exited (status 0) +++

 It works, the problem is safe_getenv(), it requires root
 permissions.

 I had the test originally without the #ifdef TEST_PROGRAM, so the
 safe_getenv() was good idea, now it's overkill. Fixed, thanks!

 $ LIBMOUNT_KERNEL_CMDLINE=tests/ts/libmount/files/kernel_cmdline \
   ltrace -e fopen,getenv ./test_mount_utils --kernel-cmdline selinux=

 getenv("LIBMOUNT_DEBUG")                          = NULL
 getenv("LIBMOUNT_KERNEL_CMDLINE")                 = "tests/ts/libmount/files/kernel_c"...
 fopen("tests/ts/libmount/files/kernel_c"..., "r") = 0x1c99010

> I.e. the utils test may only work on your PC. ;-)

  :-)

> BTW2: the libmount tests all fail when the user has set
> LIBMOUNT_DEBUG=0xffff, because the produced output differs.
> Maybe LIBMOUNT_DEBUG should be unset in tests/run.sh?

 Good idea. Implemented.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com