[PATCH v3 04/10] taint: Add TAINT_FWCTL

Jason Gunthorpe
2024-08-21T18:11:08Z

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>
---
Documentation/admin-guide/tainted-kernels.rst | 5 +++++
include/linux/panic.h | 3 ++-
kernel/panic.c | 1 +
tools/debugging/kernel-chktaint | 8 ++++++++
4 files changed, 16 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 3130e0b5116b03..bf4f276be661b7 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 f861bedc1925e7..997b18c7455cd4 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -502,6 +502,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = {
TAINT_FLAG(AUX, 'X', ' ', true),
TAINT_FLAG(RANDSTRUCT, 'T', ' ', true),
TAINT_FLAG(TEST, 'N', ' ', true),
+ TAINT_FLAG(FWCTL, 'J', ' ', true),
};

#undef TAINT_FLAG
diff --git a/tools/debugging/kernel-chktaint b/tools/debugging/kernel-chktaint
index 279be06332be99..e7da0909d09707 100755
--- a/tools/debugging/kernel-chktaint
+++ b/tools/debugging/kernel-chktaint
@@ -204,6 +204,14 @@ else
echo " * an in-kernel test (such as a KUnit test) has been run (#18)"
fi

+T=`expr $T / 2`
+if [ `expr $T % 2` -eq 0 ]; then
+ addout " "
+else
+ addout "J"
+ echo " * fwctl's mutating debug interface was used (#19)"
+fi
+
echo "For a more detailed explanation of the various taint flags see"
echo " Documentation/admin-guide/tainted-kernels.rst in the Linux kernel sources"
echo " or https://kernel.org/doc/html/latest/admin-guide/tainted-kernels.html"
--
2.46.0