netdev - Re: [PATCH v2 4/8] taint: Add TAINT

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Date: Tue, 25 Jun 2024 12:03:35 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Jason Gunthorpe <jgg@...dia.com>, Jonathan Corbet <corbet@....net>,
 Itay Avraham <itayavr@...dia.com>, Jakub Kicinski <kuba@...nel.org>,
 Leon Romanovsky <leon@...nel.org>, linux-doc@...r.kernel.org,
 linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
 Paolo Abeni <pabeni@...hat.com>, Saeed Mahameed <saeedm@...dia.com>,
 Tariq Toukan <tariqt@...dia.com>
Cc: Andy Gospodarek <andrew.gospodarek@...adcom.com>,
 Aron Silverton <aron.silverton@...cle.com>,
 Dan Williams <dan.j.williams@...el.com>, David Ahern <dsahern@...nel.org>,
 Christoph Hellwig <hch@...radead.org>, Jiri Pirko <jiri@...dia.com>,
 Leonid Bloch <lbloch@...dia.com>, Leon Romanovsky <leonro@...dia.com>,
 linux-cxl@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v2 4/8] taint: Add TAINT_FWCTL



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@...dia.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