@@ -43,6 +43,9 @@ typedef struct {
/* Active LAM mode: X86_CR3_LAM_U48 or X86_CR3_LAM_U57 or 0 (disabled) */
unsigned long lam_cr3_mask;
+
+ /* Significant bits of the virtual address. Excludes tag bits. */
+ u64 untag_mask;
#endif
struct mutex lock;
@@ -100,6 +100,12 @@ static inline unsigned long mm_lam_cr3_mask(struct mm_struct *mm)
static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
{
mm->context.lam_cr3_mask = oldmm->context.lam_cr3_mask;
+ mm->context.untag_mask = oldmm->context.untag_mask;
+}
+
+static inline void mm_reset_untag_mask(struct mm_struct *mm)
+{
+ mm->context.untag_mask = -1UL;
}
#else
@@ -112,6 +118,10 @@ static inline unsigned long mm_lam_cr3_mask(struct mm_struct *mm)
static inline void dup_lam(struct mm_struct *oldmm, struct mm_struct *mm)
{
}
+
+static inline void mm_reset_untag_mask(struct mm_struct *mm)
+{
+}
#endif
#define enter_lazy_tlb enter_lazy_tlb
@@ -138,6 +148,7 @@ static inline int init_new_context(struct task_struct *tsk,
mm->context.execute_only_pkey = -1;
}
#endif
+ mm_reset_untag_mask(mm);
init_new_context_ldt(mm);
return 0;
}
@@ -6,6 +6,7 @@
*/
#include <linux/compiler.h>
#include <linux/kasan-checks.h>
+#include <linux/mm_types.h>
#include <linux/string.h>
#include <asm/asm.h>
#include <asm/page.h>
@@ -20,6 +21,30 @@ static inline bool pagefault_disabled(void);
# define WARN_ON_IN_IRQ()
#endif
+#ifdef CONFIG_X86_64
+/*
+ * Mask out tag bits from the address.
+ *
+ * Magic with the 'sign' allows to untag userspace pointer without any branches
+ * while leaving kernel addresses intact.
+ */
+#define untagged_addr(mm, addr) ({ \
+ u64 __addr = (__force u64)(addr); \
+ s64 sign = (s64)__addr >> 63; \
+ __addr &= (mm)->context.untag_mask | sign; \
+ (__force __typeof__(addr))__addr; \
+})
+
+#define untagged_ptr(mm, ptr) ({ \
+ u64 __ptrval = (__force u64)(ptr); \
+ __ptrval = untagged_addr(mm, __ptrval); \
+ (__force __typeof__(*(ptr)) *)__ptrval; \
+})
+#else
+#define untagged_addr(mm, addr) (addr)
+#define untagged_ptr(mm, ptr) (ptr)
+#endif
+
/**
* access_ok - Checks if a user space pointer is valid
* @addr: User space pointer to start of block to check
@@ -40,7 +65,7 @@ static inline bool pagefault_disabled(void);
#define access_ok(addr, size) \
({ \
WARN_ON_IN_IRQ(); \
- likely(__access_ok(addr, size)); \
+ likely(__access_ok(untagged_addr(current->mm, addr), size)); \
})
#include <asm-generic/access_ok.h>
@@ -125,7 +150,13 @@ extern int __get_user_bad(void);
* Return: zero on success, or -EFAULT on error.
* On error, the variable @x is set to zero.
*/
-#define get_user(x,ptr) ({ might_fault(); do_get_user_call(get_user,x,ptr); })
+#define get_user(x,ptr) \
+({ \
+ __typeof__(*(ptr)) __user *__ptr_clean; \
+ __ptr_clean = untagged_ptr(current->mm, ptr); \
+ might_fault(); \
+ do_get_user_call(get_user,x,__ptr_clean); \
+})
/**
* __get_user - Get a simple variable from user space, with less checking.
@@ -222,7 +253,12 @@ extern void __put_user_nocheck_8(void);
*
* Return: zero on success, or -EFAULT on error.
*/
-#define put_user(x, ptr) ({ might_fault(); do_put_user_call(put_user,x,ptr); })
+#define put_user(x, ptr) ({ \
+ __typeof__(*(ptr)) __user *__ptr_clean; \
+ __ptr_clean = untagged_ptr(current->mm, ptr); \
+ might_fault(); \
+ do_put_user_call(put_user,x,__ptr_clean); \
+})
/**
* __put_user - Write a simple value into user space, with less checking.
@@ -47,6 +47,7 @@
#include <asm/frame.h>
#include <asm/unwind.h>
#include <asm/tdx.h>
+#include <asm/mmu_context.h>
#include "process.h"
@@ -367,6 +368,8 @@ void arch_setup_new_exec(void)
task_clear_spec_ssb_noexec(current);
speculation_ctrl_update(read_thread_flags());
}
+
+ mm_reset_untag_mask(current->mm);
}
#ifdef CONFIG_X86_IOPL_IOPERM
untagged_addr() is a helper used by the core-mm to strip tag bits and get the address to the canonical shape. In only handles userspace addresses. The untagging mask is stored in mmu_context and will be set on enabling LAM for the process. The tags must not be included into check whether it's okay to access the userspace address. Strip tags in access_ok(). get_user() and put_user() don't use access_ok(), but check access against TASK_SIZE directly in assembly. Strip tags, before calling into the assembly helper. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> --- arch/x86/include/asm/mmu.h | 3 +++ arch/x86/include/asm/mmu_context.h | 11 ++++++++ arch/x86/include/asm/uaccess.h | 42 +++++++++++++++++++++++++++--- arch/x86/kernel/process.c | 3 +++ 4 files changed, 56 insertions(+), 3 deletions(-)