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From: Christoph Hellwig <hch@lst.de>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Michael Ellerman <mpe@ellerman.id.au>,
	x86@kernel.org
Cc: Kees Cook <keescook@chromium.org>,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH 08/10] x86: remove address space overrides using set_fs()
Date: Thu, 27 Aug 2020 17:00:28 +0200	[thread overview]
Message-ID: <20200827150030.282762-9-hch@lst.de> (raw)
In-Reply-To: <20200827150030.282762-1-hch@lst.de>

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>
---
 arch/x86/Kconfig                   |  1 -
 arch/x86/ia32/ia32_aout.c          |  1 -
 arch/x86/include/asm/processor.h   | 11 +----------
 arch/x86/include/asm/thread_info.h |  2 --
 arch/x86/include/asm/uaccess.h     | 26 +-------------------------
 arch/x86/kernel/asm-offsets.c      |  3 ---
 arch/x86/lib/getuser.S             | 28 ++++++++++++++++++----------
 arch/x86/lib/putuser.S             | 21 ++++++++++++---------
 8 files changed, 32 insertions(+), 61 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index f85c13355732fe..7101ac64bb209d 100644
--- 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 ca8a657edf5977..a09fc37ead9d47 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -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;
 }
 
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 1618eeb08361a9..189573d95c3af6 100644
--- 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 267701ae3d86dd..44733a4bfc4294 100644
--- 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 ecefaffd15d4c8..a4ceda0510ea87 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -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));		\
 })
 
 /*
diff --git a/arch/x86/kernel/asm-offsets.c b/arch/x86/kernel/asm-offsets.c
index 3ca07ad552ae0c..70b7154f4bdd62 100644
--- a/arch/x86/kernel/asm-offsets.c
+++ b/arch/x86/kernel/asm-offsets.c
@@ -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);
 
diff --git a/arch/x86/lib/getuser.S b/arch/x86/lib/getuser.S
index c8a85b512796e1..ccc9808c66420a 100644
--- a/arch/x86/lib/getuser.S
+++ b/arch/x86/lib/getuser.S
@@ -35,10 +35,18 @@
 #include <asm/smap.h>
 #include <asm/export.h>
 
+#ifdef CONFIG_X86_5LEVEL
+#define LOAD_TASK_SIZE_MAX \
+	ALTERNATIVE "mov $((1 << 47) - 4096),%rdx", \
+		    "mov $((1 << 56) - 4096),%rdx", X86_FEATURE_LA57
+#else
+#define LOAD_TASK_SIZE_MAX	mov $TASK_SIZE_MAX,%_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_MAX
+	cmp %_ASM_DX,%_ASM_AX
 	jae bad_get_user
 	sbb %_ASM_DX, %_ASM_DX		/* array_index_mask_nospec() */
 	and %_ASM_DX, %_ASM_AX
@@ -53,8 +61,8 @@ 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_MAX
+	cmp %_ASM_DX,%_ASM_AX
 	jae bad_get_user
 	sbb %_ASM_DX, %_ASM_DX		/* array_index_mask_nospec() */
 	and %_ASM_DX, %_ASM_AX
@@ -69,8 +77,8 @@ 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_MAX
+	cmp %_ASM_DX,%_ASM_AX
 	jae bad_get_user
 	sbb %_ASM_DX, %_ASM_DX		/* array_index_mask_nospec() */
 	and %_ASM_DX, %_ASM_AX
@@ -86,8 +94,8 @@ 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_MAX
+	cmp %_ASM_DX,%_ASM_AX
 	jae bad_get_user
 	sbb %_ASM_DX, %_ASM_DX		/* array_index_mask_nospec() */
 	and %_ASM_DX, %_ASM_AX
@@ -99,8 +107,8 @@ SYM_FUNC_START(__get_user_8)
 #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_MAX
+	cmp %_ASM_DX,%_ASM_AX
 	jae bad_get_user_8
 	sbb %_ASM_DX, %_ASM_DX		/* array_index_mask_nospec() */
 	and %_ASM_DX, %_ASM_AX
diff --git a/arch/x86/lib/putuser.S b/arch/x86/lib/putuser.S
index 7c7c92db8497af..f5a56394985875 100644
--- a/arch/x86/lib/putuser.S
+++ b/arch/x86/lib/putuser.S
@@ -31,12 +31,18 @@
  * 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_MAX \
+	ALTERNATIVE "mov $((1 << 47) - 4096),%rbx", \
+		    "mov $((1 << 56) - 4096),%rbx", X86_FEATURE_LA57
+#else
+#define LOAD_TASK_SIZE_MAX	mov $TASK_SIZE_MAX,%_ASM_BX
+#endif
 
 .text
 SYM_FUNC_START(__put_user_1)
-	ENTER
-	cmp TASK_addr_limit(%_ASM_BX),%_ASM_CX
+	LOAD_TASK_SIZE_MAX
+	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
 	ASM_STAC
 1:	movb %al,(%_ASM_CX)
@@ -47,8 +53,7 @@ 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
+	LOAD_TASK_SIZE_MAX
 	sub $1,%_ASM_BX
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
@@ -61,8 +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
+	LOAD_TASK_SIZE_MAX
 	sub $3,%_ASM_BX
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
@@ -75,8 +79,7 @@ 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
+	LOAD_TASK_SIZE_MAX
 	sub $7,%_ASM_BX
 	cmp %_ASM_BX,%_ASM_CX
 	jae .Lbad_put_user
-- 
2.28.0


  parent reply	other threads:[~2020-08-27 15:01 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-27 15:00 remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Christoph Hellwig
2020-08-27 15:00 ` [PATCH 01/10] fs: don't allow kernel reads and writes without iter ops Christoph Hellwig
2020-08-27 15:58   ` David Laight
2020-08-29  9:23     ` 'Christoph Hellwig'
     [not found]   ` <20200901064849.GI4299@shao2-debian>
2020-09-01  7:08     ` [fs] ef30fb3c60: kernel write not supported for file /sys/kernel/softlockup_panic Christoph Hellwig
2020-08-27 15:00 ` [PATCH 02/10] fs: don't allow splice read/write without explicit ops Christoph Hellwig
2020-08-27 15:00 ` [PATCH 03/10] uaccess: add infrastructure for kernel builds with set_fs() Christoph Hellwig
2020-08-27 15:00 ` [PATCH 04/10] test_bitmap: skip user bitmap tests for !CONFIG_SET_FS Christoph Hellwig
2020-08-27 15:00 ` [PATCH 05/10] lkdtm: disable set_fs-based " Christoph Hellwig
2020-08-27 18:06   ` Linus Torvalds
2020-08-29  9:24     ` Christoph Hellwig
2020-09-01 18:52       ` Kees Cook
2020-09-01 18:57       ` Kees Cook
2020-09-02  8:09         ` Christoph Hellwig
2020-08-27 15:00 ` [PATCH 06/10] x86: move PAGE_OFFSET, TASK_SIZE & friends to page_{32,64}_types.h Christoph Hellwig
2020-08-27 15:00 ` [PATCH 07/10] x86: make TASK_SIZE_MAX usable from assembly code Christoph Hellwig
2020-08-27 15:00 ` Christoph Hellwig [this message]
2020-08-27 18:15   ` [PATCH 08/10] x86: remove address space overrides using set_fs() Linus Torvalds
2020-08-29  9:25     ` Christoph Hellwig
2020-08-27 15:00 ` [PATCH 09/10] powerpc: use non-set_fs based maccess routines Christoph Hellwig
2020-08-27 15:00 ` [PATCH 10/10] powerpc: remove address space overrides using set_fs() Christoph Hellwig
2020-09-02  6:15   ` Christophe Leroy
2020-09-02 12:36     ` Christoph Hellwig
2020-09-02 13:13       ` David Laight
2020-09-02 13:24         ` Christophe Leroy
2020-09-02 13:51           ` David Laight
2020-09-02 14:12             ` Christophe Leroy
2020-09-02 15:02               ` David Laight
2020-09-02 15:17       ` Christophe Leroy
2020-09-02 18:02         ` Linus Torvalds
2020-09-03  7:11           ` Christoph Hellwig
2020-09-03  7:27             ` Christophe Leroy
2020-09-03  8:55             ` Christophe Leroy
2020-09-03  7:20           ` Christophe Leroy
2020-08-27 15:31 ` remove the last set_fs() in common code, and remove it for x86 and powerpc v2 Christoph Hellwig
2020-09-01 17:13 ` Christophe Leroy
2020-09-01 17:25   ` Al Viro
2020-09-01 17:42     ` Matthew Wilcox
2020-09-01 18:39     ` Christophe Leroy
2020-09-01 19:01     ` Christophe Leroy
2020-09-02  8:10     ` Christoph Hellwig
2020-10-27  9:29 ` [PATCH 02/10] fs: don't allow splice read/write without explicit ops David Howells
2020-10-27  9:51 ` David Howells
2020-10-27  9:54   ` Christoph Hellwig
2020-10-27 10:38   ` David Howells

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