[RFC PATCH v2 5/6] kcov: add interrupt context guard to kcov_df_write()
Yunseong Kim <[email protected]>
| Newsgroups | org.kernel.vger.workflows,dev.linux.lists.llvm,org.kernel.vger.linux-doc,org.kernel.vger.linux-kbuild,org.kernel.vger.linux-kernel,org.kernel.vger.rust-for-linux |
|---|---|
| Message-ID | <[email protected]> |
The KCOV-Dataflow write path (kcov_df_write) only checks t->kcov_df_enabled before writing to the shared ring buffer. Unlike the standard KCOV check_kcov_mode() which rejects interrupt context, kcov_df_write() has no such protection. This means instrumented code running in hardirq, softirq, or NMI context that interrupts a task mid-write can re-enter kcov_df_write(), causing: - Data corruption in the ring buffer (interleaved records) - Out-of-order sequence counter increments - Potential faults from nested pointer dereferences Add an in_task() check to reject calls from non-task context, matching the safety model of the standard KCOV tracing path. Also suppress -Wmissing-prototypes in the eight_args_c test module Makefile, as the exported test functions intentionally lack a shared header. Signed-off-by: Yunseong Kim <[email protected]> --- kernel/kcov.c | 4 ++++ tools/kcov-dataflow/eight_args_c/Makefile | 1 + 2 files changed, 5 insertions(+) diff --git a/kernel/kcov.c b/kernel/kcov.c index d3c9c0efe961..373b8034ca5c 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -409,6 +409,10 @@ kcov_df_write(u64 type_marker, u64 pc, u64 meta, void *ptr, if (!t->kcov_df_enabled) return; + /* Reject calls from hardirq/softirq/NMI to prevent reentrant corruption. */ + if (!in_task()) + return; + area = (u64 *)t->kcov_df_area; if (!area) return; diff --git a/tools/kcov-dataflow/eight_args_c/Makefile b/tools/kcov-dataflow/eight_args_c/Makefile index de35bb541f07..038775b49435 100644 --- a/tools/kcov-dataflow/eight_args_c/Makefile +++ b/tools/kcov-dataflow/eight_args_c/Makefile @@ -1,2 +1,3 @@ obj-m := eight_args_mod.o KCOV_DATAFLOW_eight_args_mod.o := y +ccflags-y += -Wno-missing-prototypes -- 2.43.0