This is a preparatory work to allow passing of tagged user
pointers (with a top few bits other than zeroes) as syscall
arguments.
Since user can provide tagged pointer to syscalls they need
to be untagged before validating them in access_ok().
Untagging is done only if flag TIF_TAGGED_ADDR is set for
the thread. This is set via prctl() option which will be
introduced in a subsequent patch.
get_user() and put_user() don't use access_ok(), but check
access against TASK_SIZE direcly in assembly. Strip tags,
before calling into the assembly helper.
[kirill.shutemov@xxxxxxxxxxxxxxx - get/put_user() changes]
Signed-off-by: Bharata B Rao <bharata@xxxxxxx>
---
arch/x86/include/asm/thread_info.h | 2 ++
arch/x86/include/asm/uaccess.h | 28 +++++++++++++++++++++-------
2 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index ebec69c35e95..c786103a5325 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -101,6 +101,7 @@ struct thread_info {
#define TIF_BLOCKSTEP 25 /* set when we want DEBUGCTLMSR_BTF */
#define TIF_LAZY_MMU_UPDATES 27 /* task is updating the mmu lazily */
#define TIF_ADDR32 29 /* 32-bit address space on 64 bits */
+#define TIF_TAGGED_ADDR 30 /* Allow tagged user addresses */
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING (1 << TIF_SIGPENDING)
@@ -124,6 +125,7 @@ struct thread_info {
#define _TIF_BLOCKSTEP (1 << TIF_BLOCKSTEP)
#define _TIF_LAZY_MMU_UPDATES (1 << TIF_LAZY_MMU_UPDATES)
#define _TIF_ADDR32 (1 << TIF_ADDR32)
+#define _TIF_TAGGED_ADDR (1 << TIF_TAGGED_ADDR)
/* flags to check in __switch_to() */
#define _TIF_WORK_CTXSW_BASE \
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index ac96f9b2d64b..feb2e21c7e09 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -35,11 +35,15 @@ static inline bool __chk_range_not_ok(unsigned long addr, unsigned long size, un
return unlikely(addr > limit);
}
-#define __range_not_ok(addr, size, limit) \
-({ \
- __chk_user_ptr(addr); \
- __chk_range_not_ok((unsigned long __force)(addr), size, limit); \
-})
+static inline bool __range_not_ok(const void __user *addr, unsigned long size,
+ unsigned long limit)
+{
+ if (test_thread_flag(TIF_TAGGED_ADDR))
+ addr = untagged_addr(addr);
+
+ __chk_user_ptr(addr);
+ return __chk_range_not_ok((unsigned long __force)(addr), size, limit);
+}
#ifdef CONFIG_DEBUG_ATOMIC_SLEEP
static inline bool pagefault_disabled(void);
@@ -152,7 +156,12 @@ 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)) *ptr_untagged = untagged_ptr(ptr); \
+ might_fault(); \
+ do_get_user_call(get_user,x,ptr_untagged); \
+})
/**
* __get_user - Get a simple variable from user space, with less checking.
@@ -249,7 +258,12 @@ 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)) *ptr_untagged = untagged_ptr(ptr); \
+ might_fault(); \
+ do_put_user_call(put_user,x,ptr_untagged); \
+})
/**
* __put_user - Write a simple value into user space, with less checking.
--
2.25.1
