On Fri, 29 Apr 2022, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Apr 29, 2022 at 12:39:14PM +0800, David Gow wrote:
>> KUnit tests are not supposed to run on production systems: they may do
>> deliberately illegal things to trigger errors, and have security
>> implications (assertions will often deliberately leak kernel addresses).
>>
>> Add a new taint type, TAINT_KUNIT to signal that a KUnit test has been
>> run. This will be printed as 'N' (for kuNit, as K, U and T were already
>> taken).
>>
>> This should discourage people from running KUnit tests on production
>> systems, and to make it easier to tell if tests have been run
>> accidentally (by loading the wrong configuration, etc.)
>>
>> Signed-off-by: David Gow <davidgow@xxxxxxxxxx>
>> ---
>>
>> This is something I'd been thinking about for a while, and it came up
>> again, so I'm finally giving it a go.
>>
>> Two notes:
>> - I decided to add a new type of taint, as none of the existing ones
>> really seemed to fit. We could live with considering KUnit tests as
>> TAINT_WARN or TAINT_CRAP or something otherwise, but neither are quite
>> right.
>> - The taint_flags table gives a couple of checkpatch.pl errors around
>> bracket placement. I've kept the new entry consistent with what's
>> there rather than reformatting the whole table, but be prepared for
>> complaints about spaces.
>>
>> Thoughts?
>> -- David
>>
>> ---
>> Documentation/admin-guide/tainted-kernels.rst | 1 +
>> include/linux/panic.h | 3 ++-
>> kernel/panic.c | 1 +
>> lib/kunit/test.c | 4 ++++
>> 4 files changed, 8 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
>> index ceeed7b0798d..8f18fc4659d4 100644
>> --- a/Documentation/admin-guide/tainted-kernels.rst
>> +++ b/Documentation/admin-guide/tainted-kernels.rst
>> @@ -100,6 +100,7 @@ Bit Log Number Reason that got the kernel tainted
>> 15 _/K 32768 kernel has been live patched
>> 16 _/X 65536 auxiliary taint, defined for and used by distros
>> 17 _/T 131072 kernel was built with the struct randomization plugin
>> + 18 _/N 262144 a KUnit test has been run
>> === === ====== ========================================================
>>
>> Note: The character ``_`` is representing a blank in this table to make reading
>> diff --git a/include/linux/panic.h b/include/linux/panic.h
>> index f5844908a089..1d316c26bf27 100644
>> --- a/include/linux/panic.h
>> +++ b/include/linux/panic.h
>> @@ -74,7 +74,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
>> #define TAINT_LIVEPATCH 15
>> #define TAINT_AUX 16
>> #define TAINT_RANDSTRUCT 17
>> -#define TAINT_FLAGS_COUNT 18
>> +#define TAINT_KUNIT 18
>> +#define TAINT_FLAGS_COUNT 19
>> #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1)
>>
>> struct taint_flag {
>> diff --git a/kernel/panic.c b/kernel/panic.c
>> index eb4dfb932c85..b24ca63ed738 100644
>> --- a/kernel/panic.c
>> +++ b/kernel/panic.c
>> @@ -404,6 +404,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
>> [ TAINT_LIVEPATCH ] = { 'K', ' ', true },
>> [ TAINT_AUX ] = { 'X', ' ', true },
>> [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
>> + [ TAINT_KUNIT ] = { 'N', ' ', false },
>
> As kunit tests can be in modules, shouldn't this be "true" here?
>
> Overall, I like it, makes sense to me. The "N" will take some getting
> used to, and I have no idea why "T" was for "struct randomization", that
> would have allowed you to use "T" instead. Oh well.
Would you consider a patch adding more self-explanatory taint flag
strings to the output?
BR,
Jani.
--
Jani Nikula, Intel Open Source Graphics Center
