+ kmsan-allow-disabling-kmsan-checks-for-the-current-task.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kmsan: allow disabling KMSAN checks for the current task
has been added to the -mm mm-unstable branch.  Its filename is
     kmsan-allow-disabling-kmsan-checks-for-the-current-task.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kmsan-allow-disabling-kmsan-checks-for-the-current-task.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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------------------------------------------------------
From: Ilya Leoshkevich <iii@linux.ibm.com>
Subject: kmsan: allow disabling KMSAN checks for the current task
Date: Wed, 19 Jun 2024 17:43:46 +0200

Like for KASAN, it's useful to temporarily disable KMSAN checks around,
e.g., redzone accesses.  Introduce kmsan_disable_current() and
kmsan_enable_current(), which are similar to their KASAN counterparts.

Make them reentrant in order to handle memory allocations in interrupt
context.  Repurpose the allow_reporting field for this.

Link: https://lkml.kernel.org/r/20240619154530.163232-12-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 Documentation/dev-tools/kmsan.rst |   11 +++++++++--
 include/linux/kmsan.h             |   24 ++++++++++++++++++++++++
 include/linux/kmsan_types.h       |    2 +-
 mm/kmsan/core.c                   |    1 -
 mm/kmsan/hooks.c                  |   18 +++++++++++++++---
 mm/kmsan/report.c                 |    7 ++++---
 tools/objtool/check.c             |    2 ++
 7 files changed, 55 insertions(+), 10 deletions(-)

--- a/Documentation/dev-tools/kmsan.rst~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/Documentation/dev-tools/kmsan.rst
@@ -110,6 +110,13 @@ in the Makefile. Think of this as applyi
 function in the file or directory. Most users won't need KMSAN_SANITIZE, unless
 their code gets broken by KMSAN (e.g. runs at early boot time).
 
+KMSAN checks can also be temporarily disabled for the current task using
+``kmsan_disable_current()`` and ``kmsan_enable_current()`` calls. Each
+``kmsan_enable_current()`` call must be preceded by a
+``kmsan_disable_current()`` call; these call pairs may be nested. One needs to
+be careful with these calls, keeping the regions short and preferring other
+ways to disable instrumentation, where possible.
+
 Support
 =======
 
@@ -338,11 +345,11 @@ Per-task KMSAN state
 ~~~~~~~~~~~~~~~~~~~~
 
 Every task_struct has an associated KMSAN task state that holds the KMSAN
-context (see above) and a per-task flag disallowing KMSAN reports::
+context (see above) and a per-task counter disallowing KMSAN reports::
 
   struct kmsan_context {
     ...
-    bool allow_reporting;
+    unsigned int depth;
     struct kmsan_context_state cstate;
     ...
   }
--- a/include/linux/kmsan.h~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/include/linux/kmsan.h
@@ -239,6 +239,22 @@ void kmsan_unpoison_entry_regs(const str
  */
 void *kmsan_get_metadata(void *addr, bool is_origin);
 
+/*
+ * kmsan_enable_current(): Enable KMSAN for the current task.
+ *
+ * Each kmsan_enable_current() current call must be preceded by a
+ * kmsan_disable_current() call. These call pairs may be nested.
+ */
+void kmsan_enable_current(void);
+
+/*
+ * kmsan_disable_current(): Disable KMSAN for the current task.
+ *
+ * Each kmsan_disable_current() current call must be followed by a
+ * kmsan_enable_current() call. These call pairs may be nested.
+ */
+void kmsan_disable_current(void);
+
 #else
 
 static inline void kmsan_init_shadow(void)
@@ -338,6 +354,14 @@ static inline void kmsan_unpoison_entry_
 {
 }
 
+static inline void kmsan_enable_current(void)
+{
+}
+
+static inline void kmsan_disable_current(void)
+{
+}
+
 #endif
 
 #endif /* _LINUX_KMSAN_H */
--- a/include/linux/kmsan_types.h~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/include/linux/kmsan_types.h
@@ -31,7 +31,7 @@ struct kmsan_context_state {
 struct kmsan_ctx {
 	struct kmsan_context_state cstate;
 	int kmsan_in_runtime;
-	bool allow_reporting;
+	unsigned int depth;
 };
 
 #endif /* _LINUX_KMSAN_TYPES_H */
--- a/mm/kmsan/core.c~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/mm/kmsan/core.c
@@ -43,7 +43,6 @@ void kmsan_internal_task_create(struct t
 	struct thread_info *info = current_thread_info();
 
 	__memset(ctx, 0, sizeof(*ctx));
-	ctx->allow_reporting = true;
 	kmsan_internal_unpoison_memory(info, sizeof(*info), false);
 }
 
--- a/mm/kmsan/hooks.c~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/mm/kmsan/hooks.c
@@ -39,12 +39,10 @@ void kmsan_task_create(struct task_struc
 
 void kmsan_task_exit(struct task_struct *task)
 {
-	struct kmsan_ctx *ctx = &task->kmsan_ctx;
-
 	if (!kmsan_enabled || kmsan_in_runtime())
 		return;
 
-	ctx->allow_reporting = false;
+	kmsan_disable_current();
 }
 
 void kmsan_slab_alloc(struct kmem_cache *s, void *object, gfp_t flags)
@@ -424,3 +422,17 @@ void kmsan_check_memory(const void *addr
 					   REASON_ANY);
 }
 EXPORT_SYMBOL(kmsan_check_memory);
+
+void kmsan_enable_current(void)
+{
+	KMSAN_WARN_ON(current->kmsan_ctx.depth == 0);
+	current->kmsan_ctx.depth--;
+}
+EXPORT_SYMBOL(kmsan_enable_current);
+
+void kmsan_disable_current(void)
+{
+	current->kmsan_ctx.depth++;
+	KMSAN_WARN_ON(current->kmsan_ctx.depth == 0);
+}
+EXPORT_SYMBOL(kmsan_disable_current);
--- a/mm/kmsan/report.c~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/mm/kmsan/report.c
@@ -8,6 +8,7 @@
  */
 
 #include <linux/console.h>
+#include <linux/kmsan.h>
 #include <linux/moduleparam.h>
 #include <linux/stackdepot.h>
 #include <linux/stacktrace.h>
@@ -158,12 +159,12 @@ void kmsan_report(depot_stack_handle_t o
 
 	if (!kmsan_enabled)
 		return;
-	if (!current->kmsan_ctx.allow_reporting)
+	if (current->kmsan_ctx.depth)
 		return;
 	if (!origin)
 		return;
 
-	current->kmsan_ctx.allow_reporting = false;
+	kmsan_disable_current();
 	ua_flags = user_access_save();
 	raw_spin_lock(&kmsan_report_lock);
 	pr_err("=====================================================\n");
@@ -216,5 +217,5 @@ void kmsan_report(depot_stack_handle_t o
 	if (panic_on_kmsan)
 		panic("kmsan.panic set ...\n");
 	user_access_restore(ua_flags);
-	current->kmsan_ctx.allow_reporting = true;
+	kmsan_enable_current();
 }
--- a/tools/objtool/check.c~kmsan-allow-disabling-kmsan-checks-for-the-current-task
+++ a/tools/objtool/check.c
@@ -1202,6 +1202,8 @@ static const char *uaccess_safe_builtin[
 	"__sanitizer_cov_trace_switch",
 	/* KMSAN */
 	"kmsan_copy_to_user",
+	"kmsan_disable_current",
+	"kmsan_enable_current",
 	"kmsan_report",
 	"kmsan_unpoison_entry_regs",
 	"kmsan_unpoison_memory",
_

Patches currently in -mm which might be from iii@linux.ibm.com are

ftrace-unpoison-ftrace_regs-in-ftrace_ops_list_func.patch
kmsan-make-the-tests-compatible-with-kmsanpanic=1.patch
kmsan-disable-kmsan-when-deferred_struct_page_init-is-enabled.patch
kmsan-increase-the-maximum-store-size-to-4096.patch
kmsan-fix-is_bad_asm_addr-on-arches-with-overlapping-address-spaces.patch
kmsan-fix-kmsan_copy_to_user-on-arches-with-overlapping-address-spaces.patch
kmsan-remove-a-useless-assignment-from-kmsan_vmap_pages_range_noflush.patch
kmsan-remove-an-x86-specific-include-from-kmsanh.patch
kmsan-expose-kmsan_get_metadata.patch
kmsan-export-panic_on_kmsan.patch
kmsan-allow-disabling-kmsan-checks-for-the-current-task.patch
kmsan-introduce-memset_no_sanitize_memory.patch
kmsan-support-slab_poison.patch
kmsan-use-align_down-in-kmsan_get_metadata.patch
kmsan-do-not-round-up-pg_data_t-size.patch
mm-slub-let-kmsan-access-metadata.patch
mm-slub-disable-kmsan-when-checking-the-padding-bytes.patch
mm-kfence-disable-kmsan-when-checking-the-canary.patch
lib-zlib-unpoison-dfltcc-output-buffers.patch
kmsan-accept-ranges-starting-with-0-on-s390.patch
s390-boot-turn-off-kmsan.patch
s390-use-a-larger-stack-for-kmsan.patch
s390-boot-add-the-kmsan-runtime-stub.patch
s390-checksum-add-a-kmsan-check.patch
s390-cpacf-unpoison-the-results-of-cpacf_trng.patch
s390-cpumf-unpoison-stcctm-output-buffer.patch
s390-diag-unpoison-diag224-output-buffer.patch
s390-ftrace-unpoison-ftrace_regs-in-kprobe_ftrace_handler.patch
s390-irqflags-do-not-instrument-arch_local_irq_-with-kmsan.patch
s390-mm-define-kmsan-metadata-for-vmalloc-and-modules.patch
s390-string-add-kmsan-support.patch
s390-traps-unpoison-the-kernel_stack_overflows-pt_regs.patch
s390-uaccess-add-kmsan-support-to-put_user-and-get_user.patch
s390-uaccess-add-the-missing-linux-instrumentedh-include.patch
s390-unwind-disable-kmsan-checks.patch
s390-kmsan-implement-the-architecture-specific-functions.patch
kmsan-enable-on-s390.patch