On Wed, Dec 06, 2023 at 09:14:55AM -0600, Lucas De Marchi wrote:
> On Tue, Dec 05, 2023 at 04:55:22PM +0100, Ahelenia Ziemiańska wrote:
> touch foo
> sudo mount --bind foo /proc/cmdline
> This has been what I always used for local/test scenarios.
This is also what I came up with post factum, but it's clearly not obvious,
since the responding user did resort to rebooting.
> I wonder if
> this really needs a more "official" way like your are doing to be
> added to the library rather than just the tools.
I don't disagree; below is a scissor-patch that effectivaly
canonicalises modprobe -I ... to be
"unshare -rm sh -c 'mount --bind /dev/null /proc/cmdline; modprobe ...'"
(the -r is removed if you're already root).
I've used this approach (exactly this snippet in various arrangements)
extensively in various test suites to string up fake procfses,
and it ought to work in all environments you'd be validly running modprobe
(it won't work if you're non-root in a chroot: unlikely).
Best,
-- >8 --
Subject: [PATCH v2] Add modprobe -I/--ignore-cmdline
Previously, if you'd misconfigured the cmdline your system would be
completely poisoned.
In this real scenario, ixgbe.allow_supported_sfp=1,1,1,1 was set.
This yielded
[ 3852.901900] ixgbe: `1,1,1,1' invalid for parameter `allow_unsupported_sfp'
[ 3852.904595] ixgbe: unknown parameter 'allow_supported_sfp' ignored
and
# modprobe -r ixgbe
# modprobe ixgbe allow_supported_sfp=1
since, indeed,
# modprobe -nv ixgbe
insmod /lib/modules/5.16.0-1-amd64/kernel/drivers/net/ethernet/intel/ixgbe/ixgbe.ko allow_unsupported_sfp=1,1,1,1
# modprobe -nv ixgbe allow_supported_sfp=1
insmod /lib/modules/5.16.0-1-amd64/kernel/drivers/net/ethernet/intel/ixgbe/ixgbe.ko allow_unsupported_sfp=1,1,1,1 allow_supported_sfp=1
this leaves you with a tens-of-minutes-long reboot
(or with an explicit insmod, which no-one came up with at the time,
and which requires manual dependency-chasing).
With -I, the module can be correctly loaded since the cmdline-derived
parameter no longer stops the module loading:
# modprobe -nvI ixgbe allow_supported_sfp=1
insmod /lib/modules/5.16.0-1-amd64/kernel/drivers/net/ethernet/intel/ixgbe/ixgbe.ko allow_supported_sfp=1
# modprobe -I ixgbe allow_supported_sfp=1
[ 4497.032342] ixgbe: Intel(R) 10 Gigabit PCI Express Network Driver
[ 4497.034624] ixgbe: Copyright (c) 1999-2016 Intel Corporation.
This in many ways mirrors -C /dev/null and -i.
Yes, you could do this manually with
unshare -m; mount --bind /dev/null /proc/cmdline
but if you aren't primed to look for it,
or aren't familiar with the mechanism in the first place,
you can't
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@xxxxxxxxxxxxxxxxxx>
---
man/modprobe.xml | 16 ++++++++++++++++
tools/modprobe.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
2 files changed, 58 insertions(+), 1 deletion(-)
diff --git a/man/modprobe.xml b/man/modprobe.xml
index 91f9e27..ab9dbb0 100644
--- a/man/modprobe.xml
+++ b/man/modprobe.xml
@@ -47,6 +47,7 @@
<arg><option>-C <replaceable>config-file</replaceable></option></arg>
<arg><option>-n</option></arg>
<arg><option>-i</option></arg>
+ <arg><option>-I</option></arg>
<arg><option>-q</option></arg>
<arg><option>-b</option></arg>
<arg><replaceable>modulename</replaceable></arg>
@@ -58,6 +59,7 @@
<arg><option>-v</option></arg>
<arg><option>-n</option></arg>
<arg><option>-i</option></arg>
+ <arg><option>-I</option></arg>
<arg rep='repeat'><option><replaceable>modulename</replaceable></option></arg>
</cmdsynopsis>
<cmdsynopsis>
@@ -318,6 +320,20 @@
</para>
</listitem>
</varlistentry>
+ <varlistentry>
+ <term>
+ <option>-I</option>
+ </term>
+ <term>
+ <option>--ignore-cmdline</option>
+ </term>
+ <listitem>
+ <para>
+ This option causes <command>modprobe</command> to ignore
+ any configuration specified via the kernel command line.
+ </para>
+ </listitem>
+ </varlistentry>
<varlistentry>
<term>
<option>-n</option>
diff --git a/tools/modprobe.c b/tools/modprobe.c
index e891028..de013b1 100644
--- a/tools/modprobe.c
+++ b/tools/modprobe.c
@@ -21,11 +21,13 @@
#include <errno.h>
#include <getopt.h>
#include <limits.h>
+#include <sched.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
+#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/utsname.h>
@@ -59,7 +61,7 @@ static int remove_holders = 0;
static unsigned long long wait_msec = 0;
static int quiet_inuse = 0;
-static const char cmdopts_s[] = "arw:RibfDcnC:d:S:sqvVh";
+static const char cmdopts_s[] = "arw:RiIbfDcnC:d:S:sqvVh";
static const struct option cmdopts[] = {
{"all", no_argument, 0, 'a'},
@@ -72,6 +74,7 @@ static const struct option cmdopts[] = {
{"first-time", no_argument, 0, 3},
{"ignore-install", no_argument, 0, 'i'},
{"ignore-remove", no_argument, 0, 'i'},
+ {"ignore-cmdline", no_argument, 0, 'I'},
{"use-blacklist", no_argument, 0, 'b'},
{"force", no_argument, 0, 'f'},
{"force-modversion", no_argument, 0, 2},
@@ -825,6 +828,32 @@ static char **prepend_options_from_env(int *p_argc, char **orig_argv)
return new_argv;
}
+#define UNSHARE_REQ(...) if(!(__VA_ARGS__)) return false;
+#define UNSHARE_FILE(path, ...) \
+ { \
+ FILE * f = fopen(path, "we"); \
+ UNSHARE_REQ(f); \
+ fprintf(f, __VA_ARGS__); \
+ fclose(f); \
+ }
+static bool clear_cmdline(void)
+{
+ int uid = geteuid();
+ if(uid) {
+ int gid = getegid();
+ UNSHARE_REQ(!unshare(CLONE_NEWUSER));
+ UNSHARE_FILE("/proc/self/setgroups", "deny");
+ UNSHARE_FILE("/proc/self/uid_map", "0 %d 1", uid);
+ UNSHARE_FILE("/proc/self/gid_map", "0 %d 1", gid);
+ }
+
+ UNSHARE_REQ(!unshare(CLONE_NEWNS));
+ UNSHARE_REQ(!mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL));
+
+ UNSHARE_REQ(!mount("/dev/null", "/proc/cmdline", NULL, MS_BIND, NULL));
+ return true;
+}
+
static int do_modprobe(int argc, char **orig_argv)
{
struct kmod_ctx *ctx;
@@ -835,6 +864,7 @@ static int do_modprobe(int argc, char **orig_argv)
const char *dirname = NULL;
const char *root = NULL;
const char *kversion = NULL;
+ int ignore_cmdline = 0;
int use_all = 0;
int do_remove = 0;
int do_show_config = 0;
@@ -881,6 +911,9 @@ static int do_modprobe(int argc, char **orig_argv)
case 'i':
ignore_commands = 1;
break;
+ case 'I':
+ ignore_cmdline = 1;
+ break;
case 'b':
use_blacklist = 1;
break;
@@ -1004,6 +1037,14 @@ static int do_modprobe(int argc, char **orig_argv)
dirname = dirname_buf;
}
+ if (ignore_cmdline) {
+ if (!clear_cmdline()) {
+ ERR("clear_cmdline() failed!\n");
+ err = -1;
+ goto done;
+ }
+ }
+
ctx = kmod_new(dirname, config_paths);
if (!ctx) {
ERR("kmod_new() failed!\n");
--
2.39.2
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