@@ -467,6 +467,17 @@
#endif
.endm
+ .macro uaccess_mask_range_ptr, addr:req, size:req, limit:req, tmp:req
+#ifdef CONFIG_CPU_SPECTRE
+ sub \tmp, \limit, #1
+ subs \tmp, \tmp, \addr @ tmp = limit - 1 - addr
+ addhs \tmp, \tmp, #1 @ if (tmp >= 0) {
+ subhss \tmp, \tmp, \size @ tmp = limit - (addr + size) }
+ movlo \addr, #0 @ if (tmp < 0) addr = NULL
+ csdb
+#endif
+ .endm
+
.macro uaccess_disable, tmp, isb=1
#ifdef CONFIG_CPU_SW_DOMAIN_PAN
/*
@@ -100,6 +100,32 @@ static inline void set_fs(mm_segment_t fs)
__typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL), 0ULL, 0UL))
/*
+ * Sanitise a uaccess pointer such that it becomes NULL if addr+size
+ * is above the current addr_limit.
+ */
+#define uaccess_mask_range_ptr(ptr, size) \
+ ((__typeof__(ptr))__uaccess_mask_range_ptr(ptr, size))
+static inline void __user *__uaccess_mask_range_ptr(const void __user *ptr,
+ size_t size)
+{
+ void __user *safe_ptr = (void __user *)ptr;
+ unsigned long tmp;
+
+ asm volatile(
+ " sub %1, %3, #1\n"
+ " subs %1, %1, %0\n"
+ " addhs %1, %1, #1\n"
+ " subhss %1, %1, %2\n"
+ " movlo %0, #0\n"
+ : "+r" (safe_ptr), "=&r" (tmp)
+ : "r" (size), "r" (current_thread_info()->addr_limit)
+ : "cc");
+
+ csdb();
+ return safe_ptr;
+}
+
+/*
* Single-value transfer routines. They automatically use the right
* size if we just have the right pointer type. Note that the functions
* which read from user space (*get_*) need to take care not to leak
@@ -93,11 +93,7 @@ ENTRY(arm_copy_from_user)
#ifdef CONFIG_CPU_SPECTRE
get_thread_info r3
ldr r3, [r3, #TI_ADDR_LIMIT]
- adds ip, r1, r2 @ ip=addr+size
- sub r3, r3, #1 @ addr_limit - 1
- cmpcc ip, r3 @ if (addr+size > addr_limit - 1)
- movcs r1, #0 @ addr = NULL
- csdb
+ uaccess_mask_range_ptr r1, r2, r3, ip
#endif
#include "copy_template.S"
Introduce C and asm helpers to sanitize user address, taking the address range they target into account. Use asm helper for existing sanitization in __copy_from_user(). Signed-off-by: Julien Thierry <julien.thierry@arm.com> --- arch/arm/include/asm/assembler.h | 11 +++++++++++ arch/arm/include/asm/uaccess.h | 26 ++++++++++++++++++++++++++ arch/arm/lib/copy_from_user.S | 6 +----- 3 files changed, 38 insertions(+), 5 deletions(-)