diff options
| -rw-r--r-- | arch/s390/Kconfig.debug | 13 | ||||
| -rw-r--r-- | arch/s390/include/asm/uaccess.h | 12 | ||||
| -rw-r--r-- | arch/s390/lib/Makefile | 2 | ||||
| -rw-r--r-- | arch/s390/lib/usercopy.c | 8 |
4 files changed, 34 insertions, 1 deletions
diff --git a/arch/s390/Kconfig.debug b/arch/s390/Kconfig.debug index 2283933a9a93..45e0c6199f36 100644 --- a/arch/s390/Kconfig.debug +++ b/arch/s390/Kconfig.debug @@ -6,4 +6,17 @@ config TRACE_IRQFLAGS_SUPPORT source "lib/Kconfig.debug" +config DEBUG_STRICT_USER_COPY_CHECKS + bool "Strict user copy size checks" + ---help--- + Enabling this option turns a certain set of sanity checks for user + copy operations into compile time warnings. + + The copy_from_user() etc checks are there to help test if there + are sufficient security checks on the length argument of + the copy operation, by having gcc prove that the argument is + within bounds. + + If unsure, or if you run an older (pre 4.4) gcc, say N. + endmenu diff --git a/arch/s390/include/asm/uaccess.h b/arch/s390/include/asm/uaccess.h index cbf0a8745bf4..d6b1ed0ec52b 100644 --- a/arch/s390/include/asm/uaccess.h +++ b/arch/s390/include/asm/uaccess.h @@ -265,6 +265,12 @@ __copy_from_user(void *to, const void __user *from, unsigned long n) return uaccess.copy_from_user(n, from, to); } +extern void copy_from_user_overflow(void) +#ifdef CONFIG_DEBUG_STRICT_USER_COPY_CHECKS +__compiletime_warning("copy_from_user() buffer size is not provably correct") +#endif +; + /** * copy_from_user: - Copy a block of data from user space. * @to: Destination address, in kernel space. @@ -284,7 +290,13 @@ __copy_from_user(void *to, const void __user *from, unsigned long n) static inline unsigned long __must_check copy_from_user(void *to, const void __user *from, unsigned long n) { + unsigned int sz = __compiletime_object_size(to); + might_fault(); + if (unlikely(sz != -1 && sz < n)) { + copy_from_user_overflow(); + return n; + } if (access_ok(VERIFY_READ, from, n)) n = __copy_from_user(to, from, n); else diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile index 97975ec7a274..cd54a1c352af 100644 --- a/arch/s390/lib/Makefile +++ b/arch/s390/lib/Makefile @@ -2,7 +2,7 @@ # Makefile for s390-specific library files.. # -lib-y += delay.o string.o uaccess_std.o uaccess_pt.o +lib-y += delay.o string.o uaccess_std.o uaccess_pt.o usercopy.o obj-$(CONFIG_32BIT) += div64.o qrnnd.o ucmpdi2.o lib-$(CONFIG_64BIT) += uaccess_mvcos.o lib-$(CONFIG_SMP) += spinlock.o diff --git a/arch/s390/lib/usercopy.c b/arch/s390/lib/usercopy.c new file mode 100644 index 000000000000..14b363fec8a2 --- /dev/null +++ b/arch/s390/lib/usercopy.c @@ -0,0 +1,8 @@ +#include <linux/module.h> +#include <linux/bug.h> + +void copy_from_user_overflow(void) +{ + WARN(1, "Buffer overflow detected!\n"); +} +EXPORT_SYMBOL(copy_from_user_overflow); |