x86: remove address space overrides using set_fs()

Stop providing the possibility to override the address space using
set_fs() now that there is no need for that any more.  To properly
handle the TASK_SIZE_MAX checking for 4 vs 5-level page tables on
x86 a new alternative is introduced, which just like the one in
entry_64.S has to use the hardcoded virtual address bits to escape
the fact that TASK_SIZE_MAX isn't actually a constant when 5-level
page tables are enabled.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f85c133..7101ac6 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -237,7 +237,6 @@ config X86
        select HAVE_ARCH_KCSAN                  if X86_64
        select X86_FEATURE_NAMES                if PROC_FS
        select PROC_PID_ARCH_STATUS             if PROC_FS
-       select SET_FS
        imply IMA_SECURE_AND_OR_TRUSTED_BOOT    if EFI
 
 config INSTRUCTION_DECODER

diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index ca8a657..a09fc37 100644 (file)
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -239,7 +239,6 @@ beyond_if:
        (regs)->ss = __USER32_DS;
        regs->r8 = regs->r9 = regs->r10 = regs->r11 =
        regs->r12 = regs->r13 = regs->r14 = regs->r15 = 0;
-       set_fs(USER_DS);
        return 0;
 }
 

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 1618eeb..189573d 100644 (file)
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -482,10 +482,6 @@ extern unsigned int fpu_user_xstate_size;
 
 struct perf_event;
 
-typedef struct {
-       unsigned long           seg;
-} mm_segment_t;
-
 struct thread_struct {
        /* Cached TLS descriptors: */
        struct desc_struct      tls_array[GDT_ENTRY_TLS_ENTRIES];
@@ -538,8 +534,6 @@ struct thread_struct {
         */
        unsigned long           iopl_emul;
 
-       mm_segment_t            addr_limit;
-
        unsigned int            sig_on_uaccess_err:1;
 
        /* Floating point and extended processor state */
@@ -785,15 +779,12 @@ static inline void spin_lock_prefetch(const void *x)
 #define INIT_THREAD  {                                                   \
        .sp0                    = TOP_OF_INIT_STACK,                      \
        .sysenter_cs            = __KERNEL_CS,                            \
-       .addr_limit             = KERNEL_DS,                              \
 }
 
 #define KSTK_ESP(task)         (task_pt_regs(task)->sp)
 
 #else
-#define INIT_THREAD  {                                         \
-       .addr_limit             = KERNEL_DS,                    \
-}
+#define INIT_THREAD { }
 
 extern unsigned long KSTK_ESP(struct task_struct *task);
 

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 267701a..44733a4 100644 (file)
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -102,7 +102,6 @@ struct thread_info {
 #define TIF_SYSCALL_TRACEPOINT 28      /* syscall tracepoint instrumentation */
 #define TIF_ADDR32             29      /* 32-bit address space on 64 bits */
 #define TIF_X32                        30      /* 32-bit native x86-64 binary */
-#define TIF_FSCHECK            31      /* Check FS is USER_DS on return */
 
 #define _TIF_SYSCALL_TRACE     (1 << TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME     (1 << TIF_NOTIFY_RESUME)
@@ -131,7 +130,6 @@ struct thread_info {
 #define _TIF_SYSCALL_TRACEPOINT        (1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_ADDR32            (1 << TIF_ADDR32)
 #define _TIF_X32               (1 << TIF_X32)
-#define _TIF_FSCHECK           (1 << TIF_FSCHECK)
 
 /* 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 ecefaff..a4ceda0 100644 (file)
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -13,30 +13,6 @@
 #include <asm/extable.h>
 
 /*
- * The fs value determines whether argument validity checking should be
- * performed or not.  If get_fs() == USER_DS, checking is performed, with
- * get_fs() == KERNEL_DS, checking is bypassed.
- *
- * For historical reasons, these macros are grossly misnamed.
- */
-
-#define MAKE_MM_SEG(s) ((mm_segment_t) { (s) })
-
-#define KERNEL_DS      MAKE_MM_SEG(-1UL)
-#define USER_DS        MAKE_MM_SEG(TASK_SIZE_MAX)
-
-#define get_fs()       (current->thread.addr_limit)
-static inline void set_fs(mm_segment_t fs)
-{
-       current->thread.addr_limit = fs;
-       /* On user-mode return, check fs is correct */
-       set_thread_flag(TIF_FSCHECK);
-}
-
-#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
-#define user_addr_max() (current->thread.addr_limit.seg)
-
-/*
  * Test whether a block of memory is a valid user space address.
  * Returns 0 if the range is valid, nonzero otherwise.
  */
@@ -93,7 +69,7 @@ static inline bool pagefault_disabled(void);
 #define access_ok(addr, size)                                  \
 ({                                                                     \
        WARN_ON_IN_IRQ();                                               \
-       likely(!__range_not_ok(addr, size, user_addr_max()));           \
+       likely(!__range_not_ok(addr, size, TASK_SIZE_MAX));             \
 })
 
 /*

diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 3ca07ad..70b7154 100644 (file)
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -38,9 +38,6 @@ static void __used common(void)
 #endif
 
        BLANK();
-       OFFSET(TASK_addr_limit, task_struct, thread.addr_limit);
-
-       BLANK();
        OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);
 
        BLANK();

diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index c8a85b5..2f052bc 100644 (file)
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -35,10 +35,19 @@
 #include <asm/smap.h>
 #include <asm/export.h>
 
+#ifdef CONFIG_X86_5LEVEL
+#define LOAD_TASK_SIZE_MINUS_N(n) \
+       ALTERNATIVE __stringify(mov $((1 << 47) - 4096 - (n)),%rdx), \
+                   __stringify(mov $((1 << 56) - 4096 - (n)),%rdx), X86_FEATURE_LA57
+#else
+#define LOAD_TASK_SIZE_MINUS_N(n) \
+       mov $(TASK_SIZE_MAX - (n)),%_ASM_DX
+#endif
+
        .text
 SYM_FUNC_START(__get_user_1)
-       mov PER_CPU_VAR(current_task), %_ASM_DX
-       cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
+       LOAD_TASK_SIZE_MINUS_N(0)
+       cmp %_ASM_DX,%_ASM_AX
        jae bad_get_user
        sbb %_ASM_DX, %_ASM_DX          /* array_index_mask_nospec() */
        and %_ASM_DX, %_ASM_AX
@@ -51,15 +60,13 @@ SYM_FUNC_END(__get_user_1)
 EXPORT_SYMBOL(__get_user_1)
 
 SYM_FUNC_START(__get_user_2)
-       add $1,%_ASM_AX
-       jc bad_get_user
-       mov PER_CPU_VAR(current_task), %_ASM_DX
-       cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
+       LOAD_TASK_SIZE_MINUS_N(1)
+       cmp %_ASM_DX,%_ASM_AX
        jae bad_get_user
        sbb %_ASM_DX, %_ASM_DX          /* array_index_mask_nospec() */
        and %_ASM_DX, %_ASM_AX
        ASM_STAC
-2:     movzwl -1(%_ASM_AX),%edx
+2:     movzwl (%_ASM_AX),%edx
        xor %eax,%eax
        ASM_CLAC
        ret
@@ -67,15 +74,13 @@ SYM_FUNC_END(__get_user_2)
 EXPORT_SYMBOL(__get_user_2)
 
 SYM_FUNC_START(__get_user_4)
-       add $3,%_ASM_AX
-       jc bad_get_user
-       mov PER_CPU_VAR(current_task), %_ASM_DX
-       cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
+       LOAD_TASK_SIZE_MINUS_N(3)
+       cmp %_ASM_DX,%_ASM_AX
        jae bad_get_user
        sbb %_ASM_DX, %_ASM_DX          /* array_index_mask_nospec() */
        and %_ASM_DX, %_ASM_AX
        ASM_STAC
-3:     movl -3(%_ASM_AX),%edx
+3:     movl (%_ASM_AX),%edx
        xor %eax,%eax
        ASM_CLAC
        ret
@@ -84,29 +89,25 @@ EXPORT_SYMBOL(__get_user_4)
 
 SYM_FUNC_START(__get_user_8)
 #ifdef CONFIG_X86_64
-       add $7,%_ASM_AX
-       jc bad_get_user
-       mov PER_CPU_VAR(current_task), %_ASM_DX
-       cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
+       LOAD_TASK_SIZE_MINUS_N(7)
+       cmp %_ASM_DX,%_ASM_AX
        jae bad_get_user
        sbb %_ASM_DX, %_ASM_DX          /* array_index_mask_nospec() */
        and %_ASM_DX, %_ASM_AX
        ASM_STAC
-4:     movq -7(%_ASM_AX),%rdx
+4:     movq (%_ASM_AX),%rdx
        xor %eax,%eax
        ASM_CLAC
        ret
 #else
-       add $7,%_ASM_AX
-       jc bad_get_user_8
-       mov PER_CPU_VAR(current_task), %_ASM_DX
-       cmp TASK_addr_limit(%_ASM_DX),%_ASM_AX
+       LOAD_TASK_SIZE_MINUS_N(7)
+       cmp %_ASM_DX,%_ASM_AX
        jae bad_get_user_8
        sbb %_ASM_DX, %_ASM_DX          /* array_index_mask_nospec() */
        and %_ASM_DX, %_ASM_AX
        ASM_STAC
-4:     movl -7(%_ASM_AX),%edx
-5:     movl -3(%_ASM_AX),%ecx
+4:     movl (%_ASM_AX),%edx
+5:     movl 4(%_ASM_AX),%ecx
        xor %eax,%eax
        ASM_CLAC
        ret

diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S
index 7c7c92d..358239d 100644 (file)
--- a/arch/x86/lib/putuser.S
+++ b/arch/x86/lib/putuser.S
@@ -31,12 +31,19 @@
  * as they get called from within inline assembly.
  */
 
-#define ENTER  mov PER_CPU_VAR(current_task), %_ASM_BX
+#ifdef CONFIG_X86_5LEVEL
+#define LOAD_TASK_SIZE_MINUS_N(n) \
+       ALTERNATIVE __stringify(mov $((1 << 47) - 4096 - (n)),%rbx), \
+                   __stringify(mov $((1 << 56) - 4096 - (n)),%rbx), X86_FEATURE_LA57
+#else
+#define LOAD_TASK_SIZE_MINUS_N(n) \
+       mov $(TASK_SIZE_MAX - (n)),%_ASM_BX
+#endif
 
 .text
 SYM_FUNC_START(__put_user_1)
-       ENTER
-       cmp TASK_addr_limit(%_ASM_BX),%_ASM_CX
+       LOAD_TASK_SIZE_MINUS_N(0)
+       cmp %_ASM_BX,%_ASM_CX
        jae .Lbad_put_user
        ASM_STAC
 1:     movb %al,(%_ASM_CX)
@@ -47,9 +54,7 @@ SYM_FUNC_END(__put_user_1)
 EXPORT_SYMBOL(__put_user_1)
 
 SYM_FUNC_START(__put_user_2)
-       ENTER
-       mov TASK_addr_limit(%_ASM_BX),%_ASM_BX
-       sub $1,%_ASM_BX
+       LOAD_TASK_SIZE_MINUS_N(1)
        cmp %_ASM_BX,%_ASM_CX
        jae .Lbad_put_user
        ASM_STAC
@@ -61,9 +66,7 @@ SYM_FUNC_END(__put_user_2)
 EXPORT_SYMBOL(__put_user_2)
 
 SYM_FUNC_START(__put_user_4)
-       ENTER
-       mov TASK_addr_limit(%_ASM_BX),%_ASM_BX
-       sub $3,%_ASM_BX
+       LOAD_TASK_SIZE_MINUS_N(3)
        cmp %_ASM_BX,%_ASM_CX
        jae .Lbad_put_user
        ASM_STAC
@@ -75,9 +78,7 @@ SYM_FUNC_END(__put_user_4)
 EXPORT_SYMBOL(__put_user_4)
 
 SYM_FUNC_START(__put_user_8)
-       ENTER
-       mov TASK_addr_limit(%_ASM_BX),%_ASM_BX
-       sub $7,%_ASM_BX
+       LOAD_TASK_SIZE_MINUS_N(7)
        cmp %_ASM_BX,%_ASM_CX
        jae .Lbad_put_user
        ASM_STAC