Re: [PATCH v2 4/8] taint: Add TAINT_FWCTL

Randy Dunlap
2024-06-25T19:03:42Z

On 6/24/24 3:47 PM, Jason Gunthorpe wrote:
> Requesting a fwctl scope of access that includes mutating device debug
> data will cause the kernel to be tainted. Changing the device operation
> through things in the debug scope may cause the device to malfunction in
> undefined ways. This should be reflected in the TAINT flags to help any
> debuggers understand that something has been done.
>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Please also update tools/debugging/kernel-chktaint.

> ---
> Documentation/admin-guide/tainted-kernels.rst | 5 +++++
> include/linux/panic.h | 3 ++-
> kernel/panic.c | 1 +
> 3 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst
> index f92551539e8a66..f91a54966a9719 100644
> --- a/Documentation/admin-guide/tainted-kernels.rst
> +++ b/Documentation/admin-guide/tainted-kernels.rst
> @@ -101,6 +101,7 @@ Bit Log Number Reason that got the kernel tainted
> 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 an in-kernel test has been run
> + 19 _/J 524288 userspace used a mutating debug operation in fwctl
> === === ====== ========================================================
>
> Note: The character ``_`` is representing a blank in this table to make reading
> @@ -182,3 +183,7 @@ More detailed explanation for tainting
> produce extremely unusual kernel structure layouts (even performance
> pathological ones), which is important to know when debugging. Set at
> build time.
> +
> + 18) ``J`` if userpace opened /dev/fwctl/* and performed a FWTCL_RPC_DEBUG_WRITE
> + to use the devices debugging features. Device debugging features could
> + cause the device to malfunction in undefined ways.
> diff --git a/include/linux/panic.h b/include/linux/panic.h
> index 6717b15e798c38..5dfd5295effd40 100644
> --- a/include/linux/panic.h
> +++ b/include/linux/panic.h
> @@ -73,7 +73,8 @@ static inline void set_arch_panic_timeout(int timeout, int arch_default_timeout)
> #define TAINT_AUX 16
> #define TAINT_RANDSTRUCT 17
> #define TAINT_TEST 18
> -#define TAINT_FLAGS_COUNT 19
> +#define TAINT_FWCTL 19
> +#define TAINT_FLAGS_COUNT 20
> #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1)
>
> struct taint_flag {
> diff --git a/kernel/panic.c b/kernel/panic.c
> index 8bff183d6180e7..b71f573ec7c5fc 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -494,6 +494,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
> [ TAINT_AUX ] = { 'X', ' ', true },
> [ TAINT_RANDSTRUCT ] = { 'T', ' ', true },
> [ TAINT_TEST ] = { 'N', ' ', true },
> + [ TAINT_FWCTL ] = { 'J', ' ', true },
> };
>
> /**

--
~Randy