Skip to contentSkip to conversation

kasan: Disable branch tracing for core runtime

PATCH Superseded Marco Elver 4 participants 5 messages May 19, 2020 – May 22, 2020

Subsystems (2)
Memory management KASAN

v1 of 2 Superseded Latest is v2 →

lore
Share & tools
lore

Marco Elver

author
#0 lore raw

PATCH 1/1 kasan: Disable branch tracing for core runtime

During early boot, while KASAN is not yet initialized, it is possible to enter reporting code-path and end up in kasan_report(). While uninitialized, the branch there prevents generating any reports, however, under certain circumstances when branches are being traced (TRACE_BRANCH_PROFILING), we may recurse deep enough to cause kernel reboots without warning.

To prevent similar issues in future, we should disable branch tracing for the core runtime.

Link https://lore.kernel.org/lkml/20200517011732.GE24705@shao2-debian/ open here
Reported-by kernel test robot <[email protected]>
Signed-off-by Marco Elver <[email protected]>
---
 mm/kasan/Makefile  | 16 ++++++++--------
 mm/kasan/generic.c |  1 -
 2 files changed, 8 insertions(+), 9 deletions(-)
mm/kasan/Makefile +8 -8
index 434d503a6525..de3121848ddf 100644
@@ -15,14 +15,14 @@ CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)
 
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
-CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_tags_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_tags_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
 
 obj-$(CONFIG_KASAN) := common.o init.o report.o
 obj-$(CONFIG_KASAN_GENERIC) += generic.o generic_report.o quarantine.o
mm/kasan/generic.c +0 -1
index 56ff8885fe2e..098a7dbaced6 100644
@@ -15,7 +15,6 @@
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#define DISABLE_BRANCH_PROFILING
 
 #include <linux/export.h>
 #include <linux/interrupt.h>
Signature · 1 line
2.26.2.761.g0e0b3e54be-goog
Reviewed-by on v1 1/1
#1 lore raw
Quoted 59 lines · Marco Elver

During early boot, while KASAN is not yet initialized, it is possible to enter reporting code-path and end up in kasan_report(). While uninitialized, the branch there prevents generating any reports, however, under certain circumstances when branches are being traced (TRACE_BRANCH_PROFILING), we may recurse deep enough to cause kernel reboots without warning.

To prevent similar issues in future, we should disable branch tracing for the core runtime.

Link https://lore.kernel.org/lkml/20200517011732.GE24705@shao2-debian/ open here
Reported-by kernel test robot <[email protected]>
Signed-off-by Marco Elver <[email protected]>
---
 mm/kasan/Makefile  | 16 ++++++++--------
 mm/kasan/generic.c |  1 -
 2 files changed, 8 insertions(+), 9 deletions(-)
mm/kasan/Makefile +8 -8
index 434d503a6525..de3121848ddf 100644
@@ -15,14 +15,14 @@ CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)
 
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
-CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_tags_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
+CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
+CFLAGS_tags_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector) -DDISABLE_BRANCH_PROFILING
 
 obj-$(CONFIG_KASAN) := common.o init.o report.o
 obj-$(CONFIG_KASAN_GENERIC) += generic.o generic_report.o quarantine.o
mm/kasan/generic.c +0 -2
index 56ff8885fe2e..098a7dbaced6 100644
@@ -15,7 +15,6 @@
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#define DISABLE_BRANCH_PROFILING
 
 #include <linux/export.h>
 #include <linux/interrupt.h>
--
Quoted 2 lines

2.26.2.761.g0e0b3e54be-goog

Reviewed-by Andrey Konovalov <[email protected]>

Thanks!

maintainer
#2 lore raw
Quoted 9 lines · On Tue, 19 May 2020 23:05:46 +0200 Andrey Konovalov <[email protected]>…
Quoted 8 lines · Marco Elver

During early boot, while KASAN is not yet initialized, it is possible to enter reporting code-path and end up in kasan_report(). While uninitialized, the branch there prevents generating any reports, however, under certain circumstances when branches are being traced (TRACE_BRANCH_PROFILING), we may recurse deep enough to cause kernel reboots without warning.

Quoted 7 lines
Quoted 3 lines

To prevent similar issues in future, we should disable branch tracing for the core runtime.

...

Reviewed-by Andrey Konovalov <[email protected]>

Thanks, I queued this for 5.7.

#3 lore raw
In reply to Marco Elver
Quoted 23 lines · Marco Elver' via kasan-dev

During early boot, while KASAN is not yet initialized, it is possible to enter reporting code-path and end up in kasan_report(). While uninitialized, the branch there prevents generating any reports, however, under certain circumstances when branches are being traced (TRACE_BRANCH_PROFILING), we may recurse deep enough to cause kernel reboots without warning.

To prevent similar issues in future, we should disable branch tracing for the core runtime.

Link https://lore.kernel.org/lkml/20200517011732.GE24705@shao2-debian/ open here
Reported-by kernel test robot <[email protected]>
Signed-off-by Marco Elver <[email protected]>
---
 mm/kasan/Makefile  | 16 ++++++++--------
 mm/kasan/generic.c |  1 -
 2 files changed, 8 insertions(+), 9 deletions(-)
mm/kasan/Makefile +0 -0
index 434d503a6525..de3121848ddf 100644

mm/kasan/Makefile CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE) · line 24

Quoted 10 lines
mm/kasan/Makefile +0 -7
@@ -15,14 +15,14 @@ CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)
 
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
-CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)

mm/kasan/tags.c:15:9: warning: 'DISABLE_BRANCH_PROFILING' macro redefined [-Wmacro-redefined]

#define DISABLE_BRANCH_PROFILING
        ^
<command line>:6:9: note: previous definition is here
#define DISABLE_BRANCH_PROFILING 1
        ^

This?

mm/kasan/tags.c +0 -1
index 25b7734e7013..8a959fdd30e3 100644
@@ -12,7 +12,6 @@
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#define DISABLE_BRANCH_PROFILING
 
 #include <linux/export.h>
 #include <linux/interrupt.h>
author
#4 lore raw
Quoted 51 lines · Qian Cai
Quoted 23 lines · Marco Elver' via kasan-dev

During early boot, while KASAN is not yet initialized, it is possible to enter reporting code-path and end up in kasan_report(). While uninitialized, the branch there prevents generating any reports, however, under certain circumstances when branches are being traced (TRACE_BRANCH_PROFILING), we may recurse deep enough to cause kernel reboots without warning.

To prevent similar issues in future, we should disable branch tracing for the core runtime.

Link https://lore.kernel.org/lkml/20200517011732.GE24705@shao2-debian/ open here
Reported-by kernel test robot <[email protected]>
Signed-off-by Marco Elver <[email protected]>
---
 mm/kasan/Makefile  | 16 ++++++++--------
 mm/kasan/generic.c |  1 -
 2 files changed, 8 insertions(+), 9 deletions(-)
mm/kasan/Makefile +0 -0
index 434d503a6525..de3121848ddf 100644

mm/kasan/Makefile CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE) · line 24

Quoted 10 lines
mm/kasan/Makefile +0 -7
@@ -15,14 +15,14 @@ CFLAGS_REMOVE_tags_report.o = $(CC_FLAGS_FTRACE)
 
 # Function splitter causes unnecessary splits in __asan_load1/__asan_store1
 # see: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63533
-CFLAGS_common.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_generic_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_init.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_quarantine.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_report.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)
-CFLAGS_tags.o := $(call cc-option, -fno-conserve-stack -fno-stack-protector)

mm/kasan/tags.c:15:9: warning: 'DISABLE_BRANCH_PROFILING' macro redefined [-Wmacro-redefined]

#define DISABLE_BRANCH_PROFILING
        ^
<command line>:6:9: note: previous definition is here
#define DISABLE_BRANCH_PROFILING 1
        ^

This?

mm/kasan/tags.c +0 -0
index 25b7734e7013..8a959fdd30e3 100644

mm/kasan/tags.c line 17

Quoted 7 lines
mm/kasan/tags.c +0 -1
@@ -12,7 +12,6 @@
  */
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-#define DISABLE_BRANCH_PROFILING
 
 #include <linux/export.h>
 #include <linux/interrupt.h>

I missed this one, thanks! Added this to v2.

v2: https://lkml.kernel.org/r/[email protected]