[PATCH 0/6] [v2] asm-generic: strncpy_from_user/strnlen_user cleanup

[PATCH 0/6] [v2] asm-generic: strncpy_from_user/strnlen_user cleanup

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

As I've queued up some patches for asm-generic, I remembered an
older series that I created but never submitted.

These two functions appear to be unnecessarily different between
architectures, and the asm-generic version is a bit questionable,
even for NOMMU architectures.

Clean this up to just use the generic library version for anything
that uses the generic version today. I've expanded on the patch
descriptions a little, as suggested by Christoph Hellwig, but I
suspect a more detailed review would uncover additional problems
with the custom versions that are getting removed.

       Arnd

Arnd Bergmann (6):
  [v2] asm-generic/uaccess.h: remove __strncpy_from_user/__strnlen_user
  [v2] h8300: remove stale strncpy_from_user
  [v2] hexagon: use generic strncpy/strnlen from_user
  [v2] arc: use generic strncpy/strnlen from_user
  [v2] asm-generic: uaccess: remove inline
    strncpy_from_user/strnlen_user
  [v2] asm-generic: remove extra strn{cpy_from,len}_user declarations

 arch/arc/Kconfig                    |   2 +
 arch/arc/include/asm/uaccess.h      |  72 ----------------
 arch/arc/mm/extable.c               |  12 ---
 arch/h8300/Kconfig                  |   2 +
 arch/h8300/kernel/h8300_ksyms.c     |   2 -
 arch/h8300/lib/Makefile             |   2 +-
 arch/h8300/lib/strncpy.S            |  35 --------
 arch/hexagon/Kconfig                |   2 +
 arch/hexagon/include/asm/uaccess.h  |  31 -------
 arch/hexagon/kernel/hexagon_ksyms.c |   1 -
 arch/hexagon/mm/Makefile            |   2 +-
 arch/hexagon/mm/strnlen_user.S      | 126 ----------------------------
 arch/m68k/Kconfig                   |   4 +-
 arch/riscv/Kconfig                  |   4 +-
 arch/um/include/asm/uaccess.h       |   5 +-
 arch/um/kernel/skas/uaccess.c       |   5 +-
 include/asm-generic/uaccess.h       |  52 ++----------
 17 files changed, 25 insertions(+), 334 deletions(-)
 delete mode 100644 arch/h8300/lib/strncpy.S
 delete mode 100644 arch/hexagon/mm/strnlen_user.S

-- 
2.29.2

Cc: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Brian Cain <bcain@codeaurora.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Sid Manning <sidneym@codeaurora.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-hexagon@vger.kernel.org
Cc: linux-m68k@lists.linux-m68k.org
Cc: linux-riscv@lists.infradead.org
Cc: linux-um@lists.infradead.org
Cc: linux-arch@vger.kernel.org

[PATCH 1/6] [v2] asm-generic/uaccess.h: remove __strncpy_from_user/__strnlen_user

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

This is a preparation for changing over architectures to the
generic implementation one at a time. As there are no callers
of either __strncpy_from_user() or __strnlen_user(), fold these
into the strncpy_from_user() strnlen_user() functions to make
each implementation independent of the others.

Many of these implementations have known bugs, but the intention
here is to not change behavior at all and stay compatible with
those bugs for the moment.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arc/include/asm/uaccess.h     | 14 ++++++++++----
 arch/hexagon/include/asm/uaccess.h | 22 +++++++++++++---------
 arch/um/include/asm/uaccess.h      |  8 ++++----
 arch/um/kernel/skas/uaccess.c      |  5 ++++-
 include/asm-generic/uaccess.h      | 28 +++++++++++-----------------
 5 files changed, 42 insertions(+), 35 deletions(-)

diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index ea40ec7f6cae..3476348f361e 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -661,6 +661,9 @@ __arc_strncpy_from_user(char *dst, const char __user *src, long count)
 	long res = 0;
 	char val;
 
+	if (!access_ok(src, 1))
+		return -EFAULT;
+
 	if (count == 0)
 		return 0;
 
@@ -693,6 +696,9 @@ static inline long __arc_strnlen_user(const char __user *s, long n)
 	long res, tmp1, cnt;
 	char val;
 
+	if (!access_ok(s, 1))
+		return 0;
+
 	__asm__ __volatile__(
 	"	mov %2, %1			\n"
 	"1:	ldb.ab  %3, [%0, 1]		\n"
@@ -724,8 +730,8 @@ static inline long __arc_strnlen_user(const char __user *s, long n)
 #define INLINE_COPY_FROM_USER
 
 #define __clear_user(d, n)		__arc_clear_user(d, n)
-#define __strncpy_from_user(d, s, n)	__arc_strncpy_from_user(d, s, n)
-#define __strnlen_user(s, n)		__arc_strnlen_user(s, n)
+#define strncpy_from_user(d, s, n)	__arc_strncpy_from_user(d, s, n)
+#define strnlen_user(s, n)		__arc_strnlen_user(s, n)
 #else
 extern unsigned long arc_clear_user_noinline(void __user *to,
 		unsigned long n);
@@ -734,8 +740,8 @@ extern long arc_strncpy_from_user_noinline (char *dst, const char __user *src,
 extern long arc_strnlen_user_noinline(const char __user *src, long n);
 
 #define __clear_user(d, n)		arc_clear_user_noinline(d, n)
-#define __strncpy_from_user(d, s, n)	arc_strncpy_from_user_noinline(d, s, n)
-#define __strnlen_user(s, n)		arc_strnlen_user_noinline(s, n)
+#define strncpy_from_user(d, s, n)	arc_strncpy_from_user_noinline(d, s, n)
+#define strnlen_user(s, n)		arc_strnlen_user_noinline(s, n)
 
 #endif
 
diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index c1019a736ff1..59aa3a50744f 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -57,23 +57,27 @@ unsigned long raw_copy_to_user(void __user *to, const void *from,
 __kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
 #define __clear_user(a, s) __clear_user_hexagon((a), (s))
 
-#define __strncpy_from_user(dst, src, n) hexagon_strncpy_from_user(dst, src, n)
+extern long __strnlen_user(const char __user *src, long n);
 
-/*  get around the ifndef in asm-generic/uaccess.h  */
-#define __strnlen_user __strnlen_user
+static inline strnlen_user(const char __user *src, long n)
+{
+        if (!access_ok(src, 1))
+		return 0;
 
-extern long __strnlen_user(const char __user *src, long n);
+	return __strnlen_user(src, n);
+}
+/*  get around the ifndef in asm-generic/uaccess.h  */
+#define strnlen_user strnlen_user
 
-static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
-					     long n);
+static inline long strncpy_from_user(char *dst, const char __user *src, long n);
+#define strncpy_from_user strncpy_from_user
 
 #include <asm-generic/uaccess.h>
 
 /*  Todo:  an actual accelerated version of this.  */
-static inline long hexagon_strncpy_from_user(char *dst, const char __user *src,
-					     long n)
+static inline long strncpy_from_user(char *dst, const char __user *src, long n)
 {
-	long res = __strnlen_user(src, n);
+	long res = strnlen_user(src, n);
 
 	if (unlikely(!res))
 		return -EFAULT;
diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h
index fe66d659acad..3bf209f683f8 100644
--- a/arch/um/include/asm/uaccess.h
+++ b/arch/um/include/asm/uaccess.h
@@ -23,16 +23,16 @@
 
 extern unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n);
 extern unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n);
-extern long __strncpy_from_user(char *dst, const char __user *src, long count);
-extern long __strnlen_user(const void __user *str, long len);
+extern long strncpy_from_user(char *dst, const char __user *src, long count);
+extern long strnlen_user(const void __user *str, long len);
 extern unsigned long __clear_user(void __user *mem, unsigned long len);
 static inline int __access_ok(unsigned long addr, unsigned long size);
 
 /* Teach asm-generic/uaccess.h that we have C functions for these. */
 #define __access_ok __access_ok
 #define __clear_user __clear_user
-#define __strnlen_user __strnlen_user
-#define __strncpy_from_user __strncpy_from_user
+#define strnlen_user strnlen_user
+#define strncpy_from_user strncpy_from_user
 #define INLINE_COPY_FROM_USER
 #define INLINE_COPY_TO_USER
 
diff --git a/arch/um/kernel/skas/uaccess.c b/arch/um/kernel/skas/uaccess.c
index 2dec915abe6f..205679cc4bb7 100644
--- a/arch/um/kernel/skas/uaccess.c
+++ b/arch/um/kernel/skas/uaccess.c
@@ -188,11 +188,14 @@ static int strncpy_chunk_from_user(unsigned long from, int len, void *arg)
 	return 0;
 }
 
-long __strncpy_from_user(char *dst, const char __user *src, long count)
+long strncpy_from_user(char *dst, const char __user *src, long count)
 {
 	long n;
 	char *ptr = dst;
 
+	if (!access_ok(src, 1))
+		return -EFAULT;
+
 	if (uaccess_kernel()) {
 		strncpy(dst, (__force void *) src, count);
 		return strnlen(dst, count);
diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index 4973328f3c6e..c03889cc904c 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -246,11 +246,15 @@ extern int __get_user_bad(void) __attribute__((noreturn));
 /*
  * Copy a null terminated string from userspace.
  */
-#ifndef __strncpy_from_user
+#ifndef strncpy_from_user
 static inline long
-__strncpy_from_user(char *dst, const char __user *src, long count)
+strncpy_from_user(char *dst, const char __user *src, long count)
 {
 	char *tmp;
+
+	if (!access_ok(src, 1))
+		return -EFAULT;
+
 	strncpy(dst, (const char __force *)src, count);
 	for (tmp = dst; *tmp && count > 0; tmp++, count--)
 		;
@@ -258,24 +262,12 @@ __strncpy_from_user(char *dst, const char __user *src, long count)
 }
 #endif
 
-static inline long
-strncpy_from_user(char *dst, const char __user *src, long count)
-{
-	if (!access_ok(src, 1))
-		return -EFAULT;
-	return __strncpy_from_user(dst, src, count);
-}
-
+#ifndef strnlen_user
 /*
  * Return the size of a string (including the ending 0)
  *
  * Return 0 on exception, a value greater than N if too long
- */
-#ifndef __strnlen_user
-#define __strnlen_user(s, n) (strnlen((s), (n)) + 1)
-#endif
-
-/*
+ *
  * Unlike strnlen, strnlen_user includes the nul terminator in
  * its returned count. Callers should check for a returned value
  * greater than N as an indication the string is too long.
@@ -284,8 +276,10 @@ static inline long strnlen_user(const char __user *src, long n)
 {
 	if (!access_ok(src, 1))
 		return 0;
-	return __strnlen_user(src, n);
+
+	return strnlen(src, n) + 1;
 }
+#endif
 
 /*
  * Zero Userspace
-- 
2.29.2

[PATCH 2/6] [v2] h8300: remove stale strncpy_from_user

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

This function is never called because h8300 uses the asm-generic
inline function version.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/h8300/kernel/h8300_ksyms.c |  2 --
 arch/h8300/lib/Makefile         |  2 +-
 arch/h8300/lib/strncpy.S        | 35 ---------------------------------
 3 files changed, 1 insertion(+), 38 deletions(-)
 delete mode 100644 arch/h8300/lib/strncpy.S

diff --git a/arch/h8300/kernel/h8300_ksyms.c b/arch/h8300/kernel/h8300_ksyms.c
index 1c6f902e82a5..853d6e886477 100644
--- a/arch/h8300/kernel/h8300_ksyms.c
+++ b/arch/h8300/kernel/h8300_ksyms.c
@@ -19,7 +19,6 @@ asmlinkage long __mulsi3(long, long);
 asmlinkage long __udivsi3(long, long);
 asmlinkage void *memcpy(void *, const void *, size_t);
 asmlinkage void *memset(void *, int, size_t);
-asmlinkage long strncpy_from_user(void *to, void *from, size_t n);
 
 	/* gcc lib functions */
 EXPORT_SYMBOL(__ucmpdi2);
@@ -34,4 +33,3 @@ EXPORT_SYMBOL(__mulsi3);
 EXPORT_SYMBOL(__udivsi3);
 EXPORT_SYMBOL(memcpy);
 EXPORT_SYMBOL(memset);
-EXPORT_SYMBOL(strncpy_from_user);
diff --git a/arch/h8300/lib/Makefile b/arch/h8300/lib/Makefile
index 685fa837c1f7..5911c1fa856d 100644
--- a/arch/h8300/lib/Makefile
+++ b/arch/h8300/lib/Makefile
@@ -3,7 +3,7 @@
 # Makefile for H8/300-specific library files..
 #
 
-lib-y  = memcpy.o memset.o abs.o strncpy.o \
+lib-y  = memcpy.o memset.o abs.o \
 	 mulsi3.o udivsi3.o muldi3.o moddivsi3.o \
 	 ashldi3.o lshrdi3.o ashrdi3.o ucmpdi2.o \
 	 delay.o
diff --git a/arch/h8300/lib/strncpy.S b/arch/h8300/lib/strncpy.S
deleted file mode 100644
index 8b65d7c4727b..000000000000
--- a/arch/h8300/lib/strncpy.S
+++ /dev/null
@@ -1,35 +0,0 @@
-;;; SPDX-License-Identifier: GPL-2.0
-;;; strncpy.S
-
-#include <asm/linkage.h>
-
-	.text
-.global strncpy_from_user
-
-;;; long strncpy_from_user(void *to, void *from, size_t n)
-strncpy_from_user:
-	mov.l	er2,er2
-	bne	1f
-	sub.l	er0,er0
-	rts
-1:
-	mov.l	er4,@-sp
-	sub.l	er3,er3
-2:
-	mov.b	@er1+,r4l
-	mov.b	r4l,@er0
-	adds	#1,er0
-	beq	3f
-	inc.l	#1,er3
-	dec.l	#1,er2
-	bne	2b
-3:
-	dec.l	#1,er2
-4:
-	mov.b	r4l,@er0
-	adds	#1,er0
-	dec.l	#1,er2
-	bne	4b
-	mov.l	er3,er0
-	mov.l	@sp+,er4
-	rts
-- 
2.29.2

[PATCH 3/6] [v2] hexagon: use generic strncpy/strnlen from_user

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Most per-architecture versions of these functions are broken in some form,
and they are almost certainly slower than the generic code as well.

Remove the ones for hexagon and instead use the generic version.
This custom version reads the data twice for strncpy() by doing an extra
strnlen(), and it apparently lacks a check for user_addr_max().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/hexagon/Kconfig                |   2 +
 arch/hexagon/include/asm/uaccess.h  |  33 +-------
 arch/hexagon/kernel/hexagon_ksyms.c |   1 -
 arch/hexagon/mm/Makefile            |   2 +-
 arch/hexagon/mm/strnlen_user.S      | 126 ----------------------------
 5 files changed, 5 insertions(+), 159 deletions(-)
 delete mode 100644 arch/hexagon/mm/strnlen_user.S

diff --git a/arch/hexagon/Kconfig b/arch/hexagon/Kconfig
index f18ec6f49c15..d094186188df 100644
--- a/arch/hexagon/Kconfig
+++ b/arch/hexagon/Kconfig
@@ -19,6 +19,8 @@ config HEXAGON
 	# GENERIC_ALLOCATOR is used by dma_alloc_coherent()
 	select GENERIC_ALLOCATOR
 	select GENERIC_IRQ_SHOW
+	select GENERIC_STRNCPY_FROM_USER
+	select GENERIC_STRNLEN_USER
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
 	select NEED_SG_DMA_LENGTH
diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index 59aa3a50744f..d950df12d8c5 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -57,42 +57,13 @@ unsigned long raw_copy_to_user(void __user *to, const void *from,
 __kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
 #define __clear_user(a, s) __clear_user_hexagon((a), (s))
 
-extern long __strnlen_user(const char __user *src, long n);
-
-static inline strnlen_user(const char __user *src, long n)
-{
-        if (!access_ok(src, 1))
-		return 0;
-
-	return __strnlen_user(src, n);
-}
-/*  get around the ifndef in asm-generic/uaccess.h  */
+extern long strnlen_user(const char __user *src, long n);
 #define strnlen_user strnlen_user
 
-static inline long strncpy_from_user(char *dst, const char __user *src, long n);
+extern long strncpy_from_user(char *dst, const char __user *src, long n)
 #define strncpy_from_user strncpy_from_user
 
 #include <asm-generic/uaccess.h>
 
-/*  Todo:  an actual accelerated version of this.  */
-static inline long strncpy_from_user(char *dst, const char __user *src, long n)
-{
-	long res = strnlen_user(src, n);
-
-	if (unlikely(!res))
-		return -EFAULT;
-
-	if (res > n) {
-		long left = raw_copy_from_user(dst, src, n);
-		if (unlikely(left))
-			memset(dst + (n - left), 0, left);
-		return n;
-	} else {
-		long left = raw_copy_from_user(dst, src, res);
-		if (unlikely(left))
-			memset(dst + (res - left), 0, left);
-		return res-1;
-	}
-}
 
 #endif
diff --git a/arch/hexagon/kernel/hexagon_ksyms.c b/arch/hexagon/kernel/hexagon_ksyms.c
index 35545a7386a0..ec56ce2d92a2 100644
--- a/arch/hexagon/kernel/hexagon_ksyms.c
+++ b/arch/hexagon/kernel/hexagon_ksyms.c
@@ -15,7 +15,6 @@ EXPORT_SYMBOL(__clear_user_hexagon);
 EXPORT_SYMBOL(raw_copy_from_user);
 EXPORT_SYMBOL(raw_copy_to_user);
 EXPORT_SYMBOL(iounmap);
-EXPORT_SYMBOL(__strnlen_user);
 EXPORT_SYMBOL(__vmgetie);
 EXPORT_SYMBOL(__vmsetie);
 EXPORT_SYMBOL(__vmyield);
diff --git a/arch/hexagon/mm/Makefile b/arch/hexagon/mm/Makefile
index 893838499591..49911a906fd0 100644
--- a/arch/hexagon/mm/Makefile
+++ b/arch/hexagon/mm/Makefile
@@ -4,4 +4,4 @@
 #
 
 obj-y := init.o ioremap.o uaccess.o vm_fault.o cache.o
-obj-y += copy_to_user.o copy_from_user.o strnlen_user.o vm_tlb.o
+obj-y += copy_to_user.o copy_from_user.o vm_tlb.o
diff --git a/arch/hexagon/mm/strnlen_user.S b/arch/hexagon/mm/strnlen_user.S
deleted file mode 100644
index 4b5574a7cc9c..000000000000
--- a/arch/hexagon/mm/strnlen_user.S
+++ /dev/null
@@ -1,126 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * User string length functions for kernel
- *
- * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved.
- */
-
-#define isrc	r0
-#define max	r1	/*  Do not change!  */
-
-#define end	r2
-#define tmp1	r3
-
-#define obo	r6	/*  off-by-one  */
-#define start	r7
-#define mod8	r8
-#define dbuf    r15:14
-#define dcmp	r13:12
-
-/*
- * The vector mask version of this turned out *really* badly.
- * The hardware loop version also turned out *really* badly.
- * Seems straight pointer arithmetic basically wins here.
- */
-
-#define fname __strnlen_user
-
-	.text
-	.global fname
-	.type fname, @function
-	.p2align 5  /*  why?  */
-fname:
-	{
-		mod8 = and(isrc,#7);
-		end = add(isrc,max);
-		start = isrc;
-	}
-	{
-		P0 = cmp.eq(mod8,#0);
-		mod8 = and(end,#7);
-		dcmp = #0;
-		if (P0.new) jump:t dw_loop;	/*  fire up the oven  */
-	}
-
-alignment_loop:
-fail_1:	{
-		tmp1 = memb(start++#1);
-	}
-	{
-		P0 = cmp.eq(tmp1,#0);
-		if (P0.new) jump:nt exit_found;
-		P1 = cmp.gtu(end,start);
-		mod8 = and(start,#7);
-	}
-	{
-		if (!P1) jump exit_error;  /*  hit the end  */
-		P0 = cmp.eq(mod8,#0);
-	}
-	{
-		if (!P0) jump alignment_loop;
-	}
-
-
-
-dw_loop:
-fail_2:	{
-		dbuf = memd(start);
-		obo = add(start,#1);
-	}
-	{
-		P0 = vcmpb.eq(dbuf,dcmp);
-	}
-	{
-		tmp1 = P0;
-		P0 = cmp.gtu(end,start);
-	}
-	{
-		tmp1 = ct0(tmp1);
-		mod8 = and(end,#7);
-		if (!P0) jump end_check;
-	}
-	{
-		P0 = cmp.eq(tmp1,#32);
-		if (!P0.new) jump:nt exit_found;
-		if (!P0.new) start = add(obo,tmp1);
-	}
-	{
-		start = add(start,#8);
-		jump dw_loop;
-	}	/*  might be nice to combine these jumps...   */
-
-
-end_check:
-	{
-		P0 = cmp.gt(tmp1,mod8);
-		if (P0.new) jump:nt exit_error;	/*  neverfound!  */
-		start = add(obo,tmp1);
-	}
-
-exit_found:
-	{
-		R0 = sub(start,isrc);
-		jumpr R31;
-	}
-
-exit_error:
-	{
-		R0 = add(max,#1);
-		jumpr R31;
-	}
-
-	/*  Uh, what does the "fixup" return here?  */
-	.falign
-fix_1:
-	{
-		R0 = #0;
-		jumpr R31;
-	}
-
-	.size fname,.-fname
-
-
-.section __ex_table,"a"
-.long fail_1,fix_1
-.long fail_2,fix_1
-.previous
-- 
2.29.2

Re: [PATCH 3/6] [v2] hexagon: use generic strncpy/strnlen from_user

[Christoph Hellwig]

On Sat, May 15, 2021 at 12:18:00PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Most per-architecture versions of these functions are broken in some form,
> and they are almost certainly slower than the generic code as well.
> 
> Remove the ones for hexagon and instead use the generic version.
> This custom version reads the data twice for strncpy() by doing an extra
> strnlen(), and it apparently lacks a check for user_addr_max().

I'd be tempted to just remove the first paragraph and reword the second
as:

Remove the hexagon implementation of strncpy/strnlen and instead use the
generic versions.  The hexago version of strncpy reads the data twice by
doing an extra strnlen(), and it apparently lacks a check for
user_addr_max().

Re: [PATCH 3/6] [v2] hexagon: use generic strncpy/strnlen from_user

[Arnd Bergmann]

On Mon, May 17, 2021 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Sat, May 15, 2021 at 12:18:00PM +0200, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > Most per-architecture versions of these functions are broken in some form,
> > and they are almost certainly slower than the generic code as well.
> >
> > Remove the ones for hexagon and instead use the generic version.
> > This custom version reads the data twice for strncpy() by doing an extra
> > strnlen(), and it apparently lacks a check for user_addr_max().
>
> I'd be tempted to just remove the first paragraph and reword the second
> as:
>
> Remove the hexagon implementation of strncpy/strnlen and instead use the
> generic versions.  The hexago version of strncpy reads the data twice by
> doing an extra strnlen(), and it apparently lacks a check for
> user_addr_max().

Changed to your version now, thanks!

        Arnd

[PATCH 4/6] [v2] arc: use generic strncpy/strnlen from_user

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Most per-architecture versions of these functions are broken
in some form, and they are almost certainly slower than the
generic code as well.

This version is fairly slow because it always does byte accesses
even for aligned data, and its checks for user_addr_max() differ
from the generic code.

Remove the ones for arc and instead use the generic version.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arc/Kconfig               |  2 +
 arch/arc/include/asm/uaccess.h | 83 ++--------------------------------
 arch/arc/mm/extable.c          | 12 -----
 3 files changed, 7 insertions(+), 90 deletions(-)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 2d98501c0897..a38f403a8811 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -27,6 +27,8 @@ config ARC
 	select GENERIC_PENDING_IRQ if SMP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
+	select GENERIC_STRNCPY_FROM_USER
+	select GENERIC_STRNLEN_USER
 	select HAVE_ARCH_KGDB
 	select HAVE_ARCH_TRACEHOOK
 	select HAVE_ARCH_TRANSPARENT_HUGEPAGE if ARC_MMU_V4
diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 3476348f361e..754a23f26736 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -655,96 +655,23 @@ static inline unsigned long __arc_clear_user(void __user *to, unsigned long n)
 	return res;
 }
 
-static inline long
-__arc_strncpy_from_user(char *dst, const char __user *src, long count)
-{
-	long res = 0;
-	char val;
-
-	if (!access_ok(src, 1))
-		return -EFAULT;
-
-	if (count == 0)
-		return 0;
-
-	__asm__ __volatile__(
-	"	mov	lp_count, %5		\n"
-	"	lp	3f			\n"
-	"1:	ldb.ab  %3, [%2, 1]		\n"
-	"	breq.d	%3, 0, 3f               \n"
-	"	stb.ab  %3, [%1, 1]		\n"
-	"	add	%0, %0, 1	# Num of NON NULL bytes copied	\n"
-	"3:								\n"
-	"	.section .fixup, \"ax\"		\n"
-	"	.align 4			\n"
-	"4:	mov %0, %4		# sets @res as -EFAULT	\n"
-	"	j   3b				\n"
-	"	.previous			\n"
-	"	.section __ex_table, \"a\"	\n"
-	"	.align 4			\n"
-	"	.word   1b, 4b			\n"
-	"	.previous			\n"
-	: "+r"(res), "+r"(dst), "+r"(src), "=r"(val)
-	: "g"(-EFAULT), "r"(count)
-	: "lp_count", "memory");
-
-	return res;
-}
-
-static inline long __arc_strnlen_user(const char __user *s, long n)
-{
-	long res, tmp1, cnt;
-	char val;
-
-	if (!access_ok(s, 1))
-		return 0;
-
-	__asm__ __volatile__(
-	"	mov %2, %1			\n"
-	"1:	ldb.ab  %3, [%0, 1]		\n"
-	"	breq.d  %3, 0, 2f		\n"
-	"	sub.f   %2, %2, 1		\n"
-	"	bnz 1b				\n"
-	"	sub %2, %2, 1			\n"
-	"2:	sub %0, %1, %2			\n"
-	"3:	;nop				\n"
-	"	.section .fixup, \"ax\"		\n"
-	"	.align 4			\n"
-	"4:	mov %0, 0			\n"
-	"	j   3b				\n"
-	"	.previous			\n"
-	"	.section __ex_table, \"a\"	\n"
-	"	.align 4			\n"
-	"	.word 1b, 4b			\n"
-	"	.previous			\n"
-	: "=r"(res), "=r"(tmp1), "=r"(cnt), "=r"(val)
-	: "0"(s), "1"(n)
-	: "memory");
-
-	return res;
-}
-
 #ifndef CONFIG_CC_OPTIMIZE_FOR_SIZE
 
 #define INLINE_COPY_TO_USER
 #define INLINE_COPY_FROM_USER
 
 #define __clear_user(d, n)		__arc_clear_user(d, n)
-#define strncpy_from_user(d, s, n)	__arc_strncpy_from_user(d, s, n)
-#define strnlen_user(s, n)		__arc_strnlen_user(s, n)
 #else
 extern unsigned long arc_clear_user_noinline(void __user *to,
 		unsigned long n);
-extern long arc_strncpy_from_user_noinline (char *dst, const char __user *src,
-		long count);
-extern long arc_strnlen_user_noinline(const char __user *src, long n);
-
 #define __clear_user(d, n)		arc_clear_user_noinline(d, n)
-#define strncpy_from_user(d, s, n)	arc_strncpy_from_user_noinline(d, s, n)
-#define strnlen_user(s, n)		arc_strnlen_user_noinline(s, n)
-
 #endif
 
+extern long strncpy_from_user(char *dst, const char __user *src, long count);
+#define strncpy_from_user(d, s, n)	strncpy_from_user(d, s, n)
+extern long strnlen_user(const char __user *src, long n);
+#define strnlen_user(s, n)		strnlen_user(s, n)
+
 #include <asm/segment.h>
 #include <asm-generic/uaccess.h>
 
diff --git a/arch/arc/mm/extable.c b/arch/arc/mm/extable.c
index b06b09ddf924..4e14c4244ea2 100644
--- a/arch/arc/mm/extable.c
+++ b/arch/arc/mm/extable.c
@@ -32,16 +32,4 @@ unsigned long arc_clear_user_noinline(void __user *to,
 }
 EXPORT_SYMBOL(arc_clear_user_noinline);
 
-long arc_strncpy_from_user_noinline(char *dst, const char __user *src,
-		long count)
-{
-	return __arc_strncpy_from_user(dst, src, count);
-}
-EXPORT_SYMBOL(arc_strncpy_from_user_noinline);
-
-long arc_strnlen_user_noinline(const char __user *src, long n)
-{
-	return __arc_strnlen_user(src, n);
-}
-EXPORT_SYMBOL(arc_strnlen_user_noinline);
 #endif
-- 
2.29.2

Re: [PATCH 4/6] [v2] arc: use generic strncpy/strnlen from_user

[Christoph Hellwig]

On Sat, May 15, 2021 at 12:18:01PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Most per-architecture versions of these functions are broken
> in some form, and they are almost certainly slower than the
> generic code as well.
> 
> This version is fairly slow because it always does byte accesses
> even for aligned data, and its checks for user_addr_max() differ
> from the generic code.
> 
> Remove the ones for arc and instead use the generic version.

Same comment as for hexaon before.

Re: [PATCH 4/6] [v2] arc: use generic strncpy/strnlen from_user

[Arnd Bergmann]

On Mon, May 17, 2021 at 8:16 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Sat, May 15, 2021 at 12:18:01PM +0200, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > Most per-architecture versions of these functions are broken
> > in some form, and they are almost certainly slower than the
> > generic code as well.
> >
> > This version is fairly slow because it always does byte accesses
> > even for aligned data, and its checks for user_addr_max() differ
> > from the generic code.
> >
> > Remove the ones for arc and instead use the generic version.
>
> Same comment as for hexaon before.

Changed now.

     Arnd

[PATCH 5/6] [v2] asm-generic: uaccess: remove inline strncpy_from_user/strnlen_user

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

Consolidate the asm-generic implementation with the library version
that is used everywhere else.

These are the three versions for NOMMU kernels, which can in principle
fall back to strncpy()/strnlen() as the version in asm-generic does,
but this version is particularly inefficient when it scans the string
one byte at a time twice. The generic version also lacks a check
for user_addr_max(), but this is probably ok on NOMMU targets.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/h8300/Kconfig            |  2 ++
 arch/m68k/Kconfig             |  4 +--
 arch/riscv/Kconfig            |  4 +--
 include/asm-generic/uaccess.h | 46 ++++++-----------------------------
 4 files changed, 14 insertions(+), 42 deletions(-)

diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
index 3e3e0f16f7e0..53dfd2d47e0e 100644
--- a/arch/h8300/Kconfig
+++ b/arch/h8300/Kconfig
@@ -11,6 +11,8 @@ config H8300
 	select GENERIC_IRQ_SHOW
 	select FRAME_POINTER
 	select GENERIC_CPU_DEVICES
+	select GENERIC_STRNCPY_FROM_USER
+	select GENERIC_STRNLEN_USER
 	select MODULES_USE_ELF_RELA
 	select COMMON_CLK
 	select ARCH_WANT_FRAME_POINTERS
diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
index ed6b8050e3ed..5f1aafa7b2e2 100644
--- a/arch/m68k/Kconfig
+++ b/arch/m68k/Kconfig
@@ -17,8 +17,8 @@ config M68K
 	select GENERIC_CPU_DEVICES
 	select GENERIC_IOMAP
 	select GENERIC_IRQ_SHOW
-	select GENERIC_STRNCPY_FROM_USER if MMU
-	select GENERIC_STRNLEN_USER if MMU
+	select GENERIC_STRNCPY_FROM_USER
+	select GENERIC_STRNLEN_USER
 	select HAVE_AOUT if MMU
 	select HAVE_ASM_MODVERSIONS
 	select HAVE_DEBUG_BUGVERBOSE
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index a8ad8eb76120..ada7a2918c05 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -55,8 +55,8 @@ config RISCV
 	select GENERIC_PTDUMP if MMU
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_SMP_IDLE_THREAD
-	select GENERIC_STRNCPY_FROM_USER if MMU
-	select GENERIC_STRNLEN_USER if MMU
+	select GENERIC_STRNCPY_FROM_USER
+	select GENERIC_STRNLEN_USER
 	select GENERIC_TIME_VSYSCALL if MMU && 64BIT
 	select HANDLE_DOMAIN_IRQ
 	select HAVE_ARCH_AUDITSYSCALL
diff --git a/include/asm-generic/uaccess.h b/include/asm-generic/uaccess.h
index c03889cc904c..83a48f430951 100644
--- a/include/asm-generic/uaccess.h
+++ b/include/asm-generic/uaccess.h
@@ -119,6 +119,11 @@ static inline void set_fs(mm_segment_t fs)
 #ifndef uaccess_kernel
 #define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
 #endif
+
+#ifndef user_addr_max
+#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE)
+#endif
+
 #endif /* CONFIG_SET_FS */
 
 #define access_ok(addr, size) __access_ok((unsigned long)(addr),(size))
@@ -243,44 +248,6 @@ static inline int __get_user_fn(size_t size, const void __user *ptr, void *x)
 
 extern int __get_user_bad(void) __attribute__((noreturn));
 
-/*
- * Copy a null terminated string from userspace.
- */
-#ifndef strncpy_from_user
-static inline long
-strncpy_from_user(char *dst, const char __user *src, long count)
-{
-	char *tmp;
-
-	if (!access_ok(src, 1))
-		return -EFAULT;
-
-	strncpy(dst, (const char __force *)src, count);
-	for (tmp = dst; *tmp && count > 0; tmp++, count--)
-		;
-	return (tmp - dst);
-}
-#endif
-
-#ifndef strnlen_user
-/*
- * Return the size of a string (including the ending 0)
- *
- * Return 0 on exception, a value greater than N if too long
- *
- * Unlike strnlen, strnlen_user includes the nul terminator in
- * its returned count. Callers should check for a returned value
- * greater than N as an indication the string is too long.
- */
-static inline long strnlen_user(const char __user *src, long n)
-{
-	if (!access_ok(src, 1))
-		return 0;
-
-	return strnlen(src, n) + 1;
-}
-#endif
-
 /*
  * Zero Userspace
  */
@@ -305,4 +272,7 @@ clear_user(void __user *to, unsigned long n)
 
 #include <asm/extable.h>
 
+extern long strncpy_from_user(char *dst, const char __user *src, long count);
+extern long strnlen_user(const char __user *src, long n);
+
 #endif /* __ASM_GENERIC_UACCESS_H */
-- 
2.29.2

Re: [PATCH 5/6] [v2] asm-generic: uaccess: remove inline strncpy_from_user/strnlen_user

[Christoph Hellwig]

On Sat, May 15, 2021 at 12:18:02PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> Consolidate the asm-generic implementation with the library version
> that is used everywhere else.
> 
> These are the three versions for NOMMU kernels,

I don't get the three versions part?

> +	select GENERIC_STRNCPY_FROM_USER
> +	select GENERIC_STRNLEN_USER

Given that most architetures select the generic version I wonder
if it might be worth to add another patch to invert the logic so
that architectures with their own implementation need to sekect a symbol.

> +extern long strncpy_from_user(char *dst, const char __user *src, long count);
> +extern long strnlen_user(const char __user *src, long n);

No need for the extern here.

Re: [PATCH 5/6] [v2] asm-generic: uaccess: remove inline strncpy_from_user/strnlen_user

[Arnd Bergmann]

On Mon, May 17, 2021 at 8:20 AM Christoph Hellwig <hch@lst.de> wrote:
>
> On Sat, May 15, 2021 at 12:18:02PM +0200, Arnd Bergmann wrote:
> > From: Arnd Bergmann <arnd@arndb.de>
> >
> > Consolidate the asm-generic implementation with the library version
> > that is used everywhere else.
> >
> > These are the three versions for NOMMU kernels,
>
> I don't get the three versions part?

Right, that was confusing. Rewording to

| The inline version is used on three NOMMU architectures and is
| particularly inefficient when it scans the string one byte at a time
| twice. It also lacks a check for user_addr_max(), but this is
| probably ok on NOMMU targets.
|
| Consolidate the asm-generic implementation with the library version
| that is used everywhere else.  This version is generalized enough to
| work efficiently on both MMU and NOMMU targets, and using the
| same code everywhere reduces the potential for subtle bugs.

> > +     select GENERIC_STRNCPY_FROM_USER
> > +     select GENERIC_STRNLEN_USER
>
> Given that most architetures select the generic version I wonder
> if it might be worth to add another patch to invert the logic so
> that architectures with their own implementation need to sekect a symbol.

Done now, using 'CONFIG_ARCH_HAS_{STRNCPY_FROM,STRNLEN}_USER'.

There are still seven or eight architectures that provide their own though.

> > +extern long strncpy_from_user(char *dst, const char __user *src, long count);
> > +extern long strnlen_user(const char __user *src, long n);
>
> No need for the extern here.

Removed.

       Arnd

[PATCH 6/6] [v2] asm-generic: remove extra strn{cpy_from,len}_user declarations

[Arnd Bergmann]

From: Arnd Bergmann <arnd@arndb.de>

As these are now in asm-generic, it's no longer necessary to
declare them in the architecture.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 arch/arc/include/asm/uaccess.h     | 5 -----
 arch/hexagon/include/asm/uaccess.h | 6 ------
 arch/um/include/asm/uaccess.h      | 5 +----
 3 files changed, 1 insertion(+), 15 deletions(-)

diff --git a/arch/arc/include/asm/uaccess.h b/arch/arc/include/asm/uaccess.h
index 754a23f26736..783bfdb3bfa3 100644
--- a/arch/arc/include/asm/uaccess.h
+++ b/arch/arc/include/asm/uaccess.h
@@ -667,11 +667,6 @@ extern unsigned long arc_clear_user_noinline(void __user *to,
 #define __clear_user(d, n)		arc_clear_user_noinline(d, n)
 #endif
 
-extern long strncpy_from_user(char *dst, const char __user *src, long count);
-#define strncpy_from_user(d, s, n)	strncpy_from_user(d, s, n)
-extern long strnlen_user(const char __user *src, long n);
-#define strnlen_user(s, n)		strnlen_user(s, n)
-
 #include <asm/segment.h>
 #include <asm-generic/uaccess.h>
 
diff --git a/arch/hexagon/include/asm/uaccess.h b/arch/hexagon/include/asm/uaccess.h
index d950df12d8c5..ef5bfef8d490 100644
--- a/arch/hexagon/include/asm/uaccess.h
+++ b/arch/hexagon/include/asm/uaccess.h
@@ -57,12 +57,6 @@ unsigned long raw_copy_to_user(void __user *to, const void *from,
 __kernel_size_t __clear_user_hexagon(void __user *dest, unsigned long count);
 #define __clear_user(a, s) __clear_user_hexagon((a), (s))
 
-extern long strnlen_user(const char __user *src, long n);
-#define strnlen_user strnlen_user
-
-extern long strncpy_from_user(char *dst, const char __user *src, long n)
-#define strncpy_from_user strncpy_from_user
-
 #include <asm-generic/uaccess.h>
 
 
diff --git a/arch/um/include/asm/uaccess.h b/arch/um/include/asm/uaccess.h
index 3bf209f683f8..191ef36dd543 100644
--- a/arch/um/include/asm/uaccess.h
+++ b/arch/um/include/asm/uaccess.h
@@ -23,16 +23,13 @@
 
 extern unsigned long raw_copy_from_user(void *to, const void __user *from, unsigned long n);
 extern unsigned long raw_copy_to_user(void __user *to, const void *from, unsigned long n);
-extern long strncpy_from_user(char *dst, const char __user *src, long count);
-extern long strnlen_user(const void __user *str, long len);
 extern unsigned long __clear_user(void __user *mem, unsigned long len);
 static inline int __access_ok(unsigned long addr, unsigned long size);
 
 /* Teach asm-generic/uaccess.h that we have C functions for these. */
 #define __access_ok __access_ok
 #define __clear_user __clear_user
-#define strnlen_user strnlen_user
-#define strncpy_from_user strncpy_from_user
+
 #define INLINE_COPY_FROM_USER
 #define INLINE_COPY_TO_USER
 
-- 
2.29.2