kernel: add missing UBSAN config symbols

Enabling KERNEL_UBSAN exposes several missing symbols. Add new kernel
build options for UBSAN_BOUNDS and UBSAN_TRAP, disable CONFIG_TEST_UBSAN
in the generic kernel configs and enable CONFIG_UBSAN_MISC in generic
5.10 config. The latter symbol was removed in later kernels, as it was
causing some issues, so just disable it in 5.10 instead of adding a
build option for it.

Fixes build failures with KERNEL_UBSAN enabled.

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>

3 files changed, 26 insertions, 0 deletions

diff --git a/config/Config-kernel.in b/config/Config-kernel.in
index 2243e3e5bc..902e211ea1 100644
--- a/config/Config-kernel.in
+++ b/config/Config-kernel.in
@@ -114,6 +114,16 @@ config KERNEL_UBSAN_ALIGNMENT
 	  Enabling this option on architectures that support unaligned
 	  accesses may produce a lot of false positives.
 
+config KERNEL_UBSAN_BOUNDS
+	bool "Perform array index bounds checking"
+	depends on KERNEL_UBSAN
+	help
+	  This option enables detection of directly indexed out of bounds array
+	  accesses, where the array size is known at compile time. Note that
+	  this does not protect array overflows via bad calls to the
+	  {str,mem}*cpy() family of functions (that is addressed by
+	  FORTIFY_SOURCE).
+
 config KERNEL_UBSAN_NULL
 	bool "Enable checking of null pointers"
 	depends on KERNEL_UBSAN
@@ -121,6 +131,19 @@ config KERNEL_UBSAN_NULL
 	  This option enables detection of memory accesses via a
 	  null pointer.
 
+config KERNEL_UBSAN_TRAP
+	bool "On Sanitizer warnings, abort the running kernel code"
+	depends on KERNEL_UBSAN
+	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.
+
 config KERNEL_KASAN
 	bool "Compile the kernel with KASan: runtime memory debugger"
 	select KERNEL_SLUB_DEBUG
diff --git a/target/linux/generic/config-5.10 b/target/linux/generic/config-5.10
index 403712d0e9..604d5e4e6c 100644
--- a/target/linux/generic/config-5.10
+++ b/target/linux/generic/config-5.10
@@ -6083,6 +6083,7 @@ CONFIG_TCP_CONG_CUBIC=y
 # CONFIG_TEST_STRING_HELPERS is not set
 # CONFIG_TEST_STRSCPY is not set
 # CONFIG_TEST_SYSCTL is not set
+# CONFIG_TEST_UBSAN is not set
 # CONFIG_TEST_UDELAY is not set
 # CONFIG_TEST_USER_COPY is not set
 # CONFIG_TEST_UUID is not set
@@ -6349,6 +6350,7 @@ CONFIG_UBIFS_FS_ZLIB=y
 CONFIG_UBIFS_FS_ZSTD=y
 # CONFIG_UBSAN is not set
 CONFIG_UBSAN_ALIGNMENT=y
+# CONFIG_UBSAN_MISC is not set
 # CONFIG_UCB1400_CORE is not set
 # CONFIG_UCSI is not set
 # CONFIG_UDF_FS is not set
diff --git a/target/linux/generic/config-5.4 b/target/linux/generic/config-5.4
index c44e9cf40b..bf2b462529 100644
--- a/target/linux/generic/config-5.4
+++ b/target/linux/generic/config-5.4
@@ -5631,6 +5631,7 @@ CONFIG_TCP_CONG_CUBIC=y
 # CONFIG_TEST_STRING_HELPERS is not set
 # CONFIG_TEST_STRSCPY is not set
 # CONFIG_TEST_SYSCTL is not set
+# CONFIG_TEST_UBSAN is not set
 # CONFIG_TEST_UDELAY is not set
 # CONFIG_TEST_USER_COPY is not set
 # CONFIG_TEST_UUID is not set