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x86: remove address space overrides using set_fs()

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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>
This commit is contained in:
Christoph Hellwig 2020-09-03 16:22:40 +02:00 committed by Al Viro
parent a1d826d475
commit 47058bb54b
8 changed files with 39 additions and 77 deletions
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1
arch/x86/Kconfig
View File

@ -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

1
arch/x86/ia32/ia32_aout.c
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@ -239,7 +239,6 @@ static int load_aout_binary(struct linux_binprm *bprm)
(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;
}

11
arch/x86/include/asm/processor.h
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@ -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);

2
arch/x86/include/asm/thread_info.h
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@ -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 \

26
arch/x86/include/asm/uaccess.h
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@ -12,30 +12,6 @@
#include <asm/smap.h>
#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)); \
})
/*

3
arch/x86/kernel/asm-offsets.c
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@ -37,9 +37,6 @@ static void __used common(void)
OFFSET(TASK_stack_canary, task_struct, stack_canary);
#endif
BLANK();
OFFSET(TASK_addr_limit, task_struct, thread.addr_limit);
BLANK();
OFFSET(crypto_tfm_ctx_offset, crypto_tfm, __crt_ctx);

47
arch/x86/lib/getuser.S
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@ -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

25
arch/x86/lib/putuser.S
View File

@ -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