path: root/lib
diff options
authorKees Cook <>2020-04-06 20:12:27 -0700
committerLinus Torvalds <>2020-04-07 10:43:44 -0700
commit0887a7ebc97770c7870abf3075a2e8cd502a7f52 (patch)
tree252f41ece044990e2a10a1c58e5b9575a498deec /lib
parent7baf219982281034f8c3a806869873bf098fb611 (diff)
ubsan: add trap instrumentation option
Patch series "ubsan: Split out bounds checker", v5. This splits out the bounds checker so it can be individually used. This is enabled in Android and hopefully for syzbot. Includes LKDTM tests for behavioral corner-cases (beyond just the bounds checker), and adjusts ubsan and kasan slightly for correct panic handling. This patch (of 6): The Undefined Behavior Sanitizer can operate in two modes: warning reporting mode via lib/ubsan.c handler calls, or trap mode, which uses __builtin_trap() as the handler. Using lib/ubsan.c means the kernel image is about 5% larger (due to all the debugging text and reporting structures to capture details about the warning conditions). Using the trap mode, the image size changes are much smaller, though at the loss of the "warning only" mode. In order to give greater flexibility to system builders that want minimal changes to image size and are prepared to deal with kernel code being aborted and potentially destabilizing the system, this introduces CONFIG_UBSAN_TRAP. The resulting image sizes comparison: text data bss dec hex filename 19533663 6183037 18554956 44271656 2a38828 vmlinux.stock 19991849 7618513 18874448 46484810 2c54d4a vmlinux.ubsan 19712181 6284181 18366540 44362902 2a4ec96 vmlinux.ubsan-trap CONFIG_UBSAN=y: image +4.8% (text +2.3%, data +18.9%) CONFIG_UBSAN_TRAP=y: image +0.2% (text +0.9%, data +1.6%) Additionally adjusts the CONFIG_UBSAN Kconfig help for clarity and removes the mention of non-existing boot param "ubsan_handle". Suggested-by: Elena Petrova <> Signed-off-by: Kees Cook <> Signed-off-by: Andrew Morton <> Acked-by: Dmitry Vyukov <> Cc: Andrey Ryabinin <> Cc: Andrey Konovalov <> Cc: Alexander Potapenko <> Cc: Dan Carpenter <> Cc: "Gustavo A. R. Silva" <> Cc: Arnd Bergmann <> Cc: Ard Biesheuvel <> Link: Signed-off-by: Linus Torvalds <>
Diffstat (limited to 'lib')
2 files changed, 20 insertions, 4 deletions
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 0e04fcb3ab3d..9deb655838b0 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -5,11 +5,25 @@ config ARCH_HAS_UBSAN_SANITIZE_ALL
config UBSAN
bool "Undefined behaviour sanity checker"
- This option enables undefined behaviour sanity checker
+ This option enables the Undefined Behaviour sanity checker.
Compile-time instrumentation is used to detect various undefined
- behaviours in runtime. Various types of checks may be enabled
- via boot parameter ubsan_handle
- (see: Documentation/dev-tools/ubsan.rst).
+ behaviours at runtime. For more details, see:
+ Documentation/dev-tools/ubsan.rst
+config UBSAN_TRAP
+ bool "On Sanitizer warnings, abort the running kernel code"
+ depends on UBSAN
+ depends on $(cc-option, -fsanitize-undefined-trap-on-error)
+ help
+ Building kernels with Sanitizer features enabled tends to grow
+ the kernel size by around 5%, due to adding all the debugging
+ text on failure paths. To avoid this, Sanitizer instrumentation
+ can just issue a trap. This reduces the kernel size overhead but
+ turns all warnings (including potentially harmless conditions)
+ into full exceptions that abort the running kernel code
+ (regardless of context, locks held, etc), which may destabilize
+ the system. For some system builders this is an acceptable
+ trade-off.
bool "Enable instrumentation for the entire kernel"
diff --git a/lib/Makefile b/lib/Makefile
index 3fc06399295d..685aee60de1d 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -286,7 +286,9 @@ quiet_cmd_build_OID_registry = GEN $@
clean-files += oid_registry_data.c
obj-$(CONFIG_UCS2_STRING) += ucs2_string.o
+ifneq ($(CONFIG_UBSAN_TRAP),y)
obj-$(CONFIG_UBSAN) += ubsan.o
UBSAN_SANITIZE_ubsan.o := n
KASAN_SANITIZE_ubsan.o := n