On 06/14/2016 05:20 PM, Rusty Russell wrote:
> Prarit Bhargava <prarit@xxxxxxxxxx> writes:
>> Blacklisting a module in linux has long been a problem. The current
>> procedure is to use rd.blacklist=module_name, however, that doesn't
>> cover the case after the initramfs and before a boot prompt (where one
>> is supposed to use /etc/modprobe.d/blacklist.conf to blacklist
>> runtime loading). Using rd.shell to get an early prompt is hit-or-miss,
>> and doesn't cover all situations AFAICT.
>>
>> This patch adds this functionality of permanently blacklisting a module
>> by its name via the kernel parameter module_blacklist=module_name.
>>
>> [v2]: Rusty, use core_param() instead of __setup(), and drop struct which
>> simplifies things.
>>
>> Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
>> Cc: Jonathan Corbet <corbet@xxxxxxx>
>> Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
>> Cc: linux-doc@xxxxxxxxxxxxxxx
>> ---
>> Documentation/kernel-parameters.txt | 3 +++
>> kernel/module.c | 25 +++++++++++++++++++++++++
>> 2 files changed, 28 insertions(+)
>>
>> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
>> index 82b42c958d1c..c720b96f2efc 100644
>> --- a/Documentation/kernel-parameters.txt
>> +++ b/Documentation/kernel-parameters.txt
>> @@ -2295,6 +2295,9 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
>> Note that if CONFIG_MODULE_SIG_FORCE is set, that
>> is always true, so this option does nothing.
>>
>> + module_blacklist= [KNL] Do not load a comma-separated list of
>> + modules. Useful for debugging problem modules.
>> +
>> mousedev.tap_time=
>> [MOUSE] Maximum time between finger touching and
>> leaving touchpad surface for touch to be considered
>> diff --git a/kernel/module.c b/kernel/module.c
>> index 5f71aa63ed2a..5ff5287b19a8 100644
>> --- a/kernel/module.c
>> +++ b/kernel/module.c
>> @@ -3155,6 +3155,28 @@ int __weak module_frob_arch_sections(Elf_Ehdr *hdr,
>> return 0;
>> }
>>
>> +/* module_blacklist is a comma-separated list of module names */
>> +static char *module_blacklist;
>> +static bool blacklisted(char *module_name)
>> +{
>> + char *str, *entry;
>> +
>> + if (!module_blacklist)
>> + return false;
>> +
>> + str = module_blacklist;
>> + do {
>> + entry = strsep(&str, ",");
>> + if (!strcmp(module_name, entry)) {
>> + pr_info("module %s is blacklisted\n", module_name);
>> + return true;
>> + }
>
> strsep mangles the string; this will only work once :)
>
> This is untested, and a little ugly:
>
> len = strlen(module_name);
>
> while ((p = strstr(p, module_name)) != NULL) {
> if ((p == module_blacklist || p[-1] == ',') &&
> (p[len] == ',' || p[len] == '\0'))
> return true;
> p += len;
> }
> return false;
Hmm ... yeah, a bit ugly. I could also easily do:
str = module_blacklist;
do {
if (str != module_blacklist)
module_blacklist[strlen(str) - 1] = ',';
entry = strsep(&str, ",");
if (!strcmp(module_name, entry)) {
pr_info("module %s is blacklisted\n", module_name);
if (str != module_blacklist)
module_blacklist[strlen(str) - 1] = ',';
return true;
}
} while (str);
which results in the correct behavior AFAICT with
"module_blacklist=dummy_module,prarit_module":
On boot:
[ 23.737613] blacklist: comparing |dns_resolver| to |dummy_module|
[ 23.743713] blacklist: comparing |dns_resolver| to |prarit_module|
when attempting to load dummy_module:
[ 43.938798] blacklist: comparing |dummy_module| to |dummy_module|
[ 43.944915] module dummy_module is blacklisted
and attempting to load another module after that (in this case ixgbe):
[ 47.572557] blacklist: comparing |mdio| to |dummy_module|
[ 47.577961] blacklist: comparing |mdio| to |prarit_module|
[ 47.684713] blacklist: comparing |ixgbe| to |dummy_module|
[ 47.690202] blacklist: comparing |ixgbe| to |prarit_module|
Any objection to that version? Admittedly yours is shorter but I feel like mine
might be "easier" to read...
P.
>
> Cheers,
> Rusty.
>
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