[PATCH 40/43] kmsan: kcov: unpoison area->list in kcov_remote_area_put()
STALE1651d
From: Alexander Potapenko <glider@google.com>
Date: 2021-12-14 16:24:42
Also in:
linux-mm, lkml
Subsystem:
kcov, the rest · Maintainer:
Linus Torvalds
Revision v1 of 7 in this series.
Revisions (7)
KMSAN does not instrument kernel/kcov.c for performance reasons (with CONFIG_KCOV=y virtually every place in the kernel invokes kcov instrumentation). Therefore the tool may miss writes from kcov.c that initialize memory. When CONFIG_DEBUG_LIST is enabled, list pointers from kernel/kcov.c are passed to instrumented helpers in lib/list_debug.c, resulting in false positives. To work around these reports, we unpoison the contents of area->list after initializing it. Signed-off-by: Alexander Potapenko <glider@google.com> --- Link: https://linux-review.googlesource.com/id/Ie17f2ee47a7af58f5cdf716d585ebf0769348a5a --- kernel/kcov.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/kernel/kcov.c b/kernel/kcov.c
index 36ca640c4f8e7..88ffdddc99ba1 100644
--- a/kernel/kcov.c
+++ b/kernel/kcov.c@@ -11,6 +11,7 @@ #include <linux/fs.h> #include <linux/hashtable.h> #include <linux/init.h> +#include <linux/kmsan-checks.h> #include <linux/mm.h> #include <linux/preempt.h> #include <linux/printk.h>
@@ -152,6 +153,12 @@ static void kcov_remote_area_put(struct kcov_remote_area *area, INIT_LIST_HEAD(&area->list); area->size = size; list_add(&area->list, &kcov_remote_areas); + /* + * KMSAN doesn't instrument this file, so it may not know area->list + * is initialized. Unpoison it explicitly to avoid reports in + * kcov_remote_area_get(). + */ + kmsan_unpoison_memory(&area->list, sizeof(struct list_head)); } static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t)
--
2.34.1.173.g76aa8bc2d0-goog