From: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Since the function error injection framework in the fault injection subsystem can change the function code flow forcibly, it may cause unexpected behavior (and that is the purpose of this feature) even if it is applied to the ALLOW_ERROR_INJECTION functions. So this feature must be used only for debugging or testing purpose. To identify this in the kernel oops message, add a new taint flag for the fault injection. This taint flag will be set by either function error injection is used or the BPF use the kprobe_override on error injectable functions (identified by ALLOW_ERROR_INJECTION). Link: https://lore.kernel.org/all/20221121104403.1545f9b5@xxxxxxxxxxxxxxxxxx/T/#u Signed-off-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> --- Changes in v2: - Update kernel-chktaint. --- Documentation/admin-guide/tainted-kernels.rst | 5 +++++ include/linux/panic.h | 3 ++- kernel/fail_function.c | 2 ++ kernel/panic.c | 1 + kernel/trace/bpf_trace.c | 2 ++ tools/debugging/kernel-chktaint | 8 ++++++++ 6 files changed, 20 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/tainted-kernels.rst b/Documentation/admin-guide/tainted-kernels.rst index 92a8a07f5c43..63d7cd4f6250 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 a function-level error has been injected === === ====== ======================================================== 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. + + 19) ``J`` if a function-level error has been injected and the code path was + forcibly changed by either function error injection framework or BPF's + function override feature. diff --git a/include/linux/panic.h b/include/linux/panic.h index c7759b3f2045..2b03a02d86be 100644 --- a/include/linux/panic.h +++ b/include/linux/panic.h @@ -69,7 +69,8 @@ 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_FAULT_INJECTED 19 +#define TAINT_FLAGS_COUNT 20 #define TAINT_FLAGS_MAX ((1UL << TAINT_FLAGS_COUNT) - 1) struct taint_flag { diff --git a/kernel/fail_function.c b/kernel/fail_function.c index a7ccd2930c5f..80a743f14a2c 100644 --- a/kernel/fail_function.c +++ b/kernel/fail_function.c @@ -9,6 +9,7 @@ #include <linux/kprobes.h> #include <linux/module.h> #include <linux/mutex.h> +#include <linux/panic.h> #include <linux/slab.h> #include <linux/uaccess.h> @@ -298,6 +299,7 @@ static ssize_t fei_write(struct file *file, const char __user *buffer, fei_attr_free(attr); goto out; } + add_taint(TAINT_FAULT_INJECTED, LOCKDEP_NOW_UNRELIABLE); fei_debugfs_add_attr(attr); list_add_tail(&attr->list, &fei_attr_list); ret = count; diff --git a/kernel/panic.c b/kernel/panic.c index da323209f583..e396a5fd9bb6 100644 --- a/kernel/panic.c +++ b/kernel/panic.c @@ -426,6 +426,7 @@ const struct taint_flag taint_flags[TAINT_FLAGS_COUNT] = { [ TAINT_AUX ] = { 'X', ' ', true }, [ TAINT_RANDSTRUCT ] = { 'T', ' ', true }, [ TAINT_TEST ] = { 'N', ' ', true }, + [ TAINT_FAULT_INJECTED ] = { 'J', ' ', false }, }; /** diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 1ed08967fb97..de0614d9796c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2137,6 +2137,8 @@ int perf_event_attach_bpf_prog(struct perf_event *event, goto unlock; /* set the new array to event->tp_event and set event->prog */ + if (prog->kprobe_override) + add_taint(TAINT_FAULT_INJECTED, LOCKDEP_NOW_UNRELIABLE); event->prog = prog; event->bpf_cookie = bpf_cookie; rcu_assign_pointer(event->tp_event->prog_array, new_array); diff --git a/tools/debugging/kernel-chktaint b/tools/debugging/kernel-chktaint index 279be06332be..5eb563766041 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 " * a function level error has been injected (#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";
