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-rw-r--r--include/linux/stackprotector.h19
1 files changed, 19 insertions, 0 deletions
diff --git a/include/linux/stackprotector.h b/include/linux/stackprotector.h
index 4c678c4fec58..9c88707d9a0f 100644
--- a/include/linux/stackprotector.h
+++ b/include/linux/stackprotector.h
@@ -6,6 +6,25 @@
#include <linux/sched.h>
#include <linux/random.h>
+/*
+ * On 64-bit architectures, protect against non-terminated C string overflows
+ * by zeroing out the first byte of the canary; this leaves 56 bits of entropy.
+ */
+#ifdef CONFIG_64BIT
+# ifdef __LITTLE_ENDIAN
+# define CANARY_MASK 0xffffffffffffff00UL
+# else /* big endian, 64 bits: */
+# define CANARY_MASK 0x00ffffffffffffffUL
+# endif
+#else /* 32 bits: */
+# define CANARY_MASK 0xffffffffUL
+#endif
+
+static inline unsigned long get_random_canary(void)
+{
+ return get_random_long() & CANARY_MASK;
+}
+
#if defined(CONFIG_STACKPROTECTOR) || defined(CONFIG_ARM64_PTR_AUTH)
# include <asm/stackprotector.h>
#else