[PATCH v2 26/63] lib/string: Move helper functions out of string.c

Kees Cook
2021-08-18T06:16:15Z

The core functions of string.c are those that may be implemented by
per-architecture functions, or overloaded by FORTIFY_SOURCE. As a
result, it needs to be built with __NO_FORTIFY. Without this, macros
will collide with function declarations. This was accidentally working
due to -ffreestanding (on some architectures). Make this deterministic
by explicitly setting __NO_FORTIFY and move all the helper functions
into string_helpers.c so that they gain the fortification coverage they
had been missing.

Cc: Andy Shevchenko <andy@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Andy Lavr <andy.lavr@gmail.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
---
arch/arm/boot/compressed/string.c | 1 +
arch/s390/lib/string.c | 3 +
arch/x86/boot/compressed/misc.h | 2 +
arch/x86/boot/compressed/pgtable_64.c | 2 +
arch/x86/lib/string_32.c | 1 +
lib/string.c | 210 +-------------------------
lib/string_helpers.c | 193 +++++++++++++++++++++++
7 files changed, 208 insertions(+), 204 deletions(-)

diff --git a/arch/arm/boot/compressed/string.c b/arch/arm/boot/compressed/string.c
index 8c0fa276d994..fcc678fce045 100644
--- a/arch/arm/boot/compressed/string.c
+++ b/arch/arm/boot/compressed/string.c
@@ -5,6 +5,7 @@
* Small subset of simple string routines
*/

+#define __NO_FORTIFY
#include <linux/string.h>

/*
diff --git a/arch/s390/lib/string.c b/arch/s390/lib/string.c
index cfcdf76d6a95..392fb9f4f4db 100644
--- a/arch/s390/lib/string.c
+++ b/arch/s390/lib/string.c
@@ -8,6 +8,9 @@
*/

#define IN_ARCH_STRING_C 1
+#ifndef __NO_FORTIFY
+# define __NO_FORTIFY
+#endif

#include <linux/types.h>
#include <linux/string.h>
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 31139256859f..49bde196da9b 100644
--- a/arch/x86/boot/compressed/misc.h
+++ b/arch/x86/boot/compressed/misc.h
@@ -14,6 +14,8 @@
#undef CONFIG_KASAN
#undef CONFIG_KASAN_GENERIC

+#define __NO_FORTIFY
+
/* cpu_feature_enabled() cannot be used this early */
#define USE_EARLY_PGTABLE_L5

diff --git a/arch/x86/boot/compressed/pgtable_64.c b/arch/x86/boot/compressed/pgtable_64.c
index 2a78746f5a4c..a1733319a22a 100644
--- a/arch/x86/boot/compressed/pgtable_64.c
+++ b/arch/x86/boot/compressed/pgtable_64.c
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "misc.h"
#include <linux/efi.h>
#include <asm/e820/types.h>
#include <asm/processor.h>
diff --git a/arch/x86/lib/string_32.c b/arch/x86/lib/string_32.c
index d15fdae9656e..53b3f202267c 100644
--- a/arch/x86/lib/string_32.c
+++ b/arch/x86/lib/string_32.c
@@ -11,6 +11,7 @@
* strings.
*/

+#define __NO_FORTIFY
#include <linux/string.h>
#include <linux/export.h>

diff --git a/lib/string.c b/lib/string.c
index 4fec38fc6e58..4e111d9dd6d5 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -6,20 +6,15 @@
*/

/*
- * stupid library routines.. The optimized versions should generally be found
- * as inline code in <asm-xx/string.h>
+ * This file should be used only for "library" routines that may have
+ * alternative implementations on specific architectures (generally
+ * found in <asm-xx/string.h>), or get overloaded by FORTIFY_SOURCE.
+ * (Specifically, this file is built with __NO_FORTIFY.)
*
- * These are buggy as well..
- *
- * * Fri Jun 25 1999, Ingo Oeser <ioe@informatik.tu-chemnitz.de>
- * - Added strsep() which will replace strtok() soon (because strsep() is
- * reentrant and should be faster). Use only strsep() in new code, please.
- *
- * * Sat Feb 09 2002, Jason Thomas <jason@topic.com.au>,
- * Matthew Hawkins <matt@mh.dropbear.id.au>
- * - Kissed strtok() goodbye
+ * Other helper functions should live in string_helpers.c.
*/

+#define __NO_FORTIFY
#include <linux/types.h>
#include <linux/string.h>
#include <linux/ctype.h>
@@ -254,40 +249,6 @@ ssize_t strscpy(char *dest, const char *src, size_t count)
EXPORT_SYMBOL(strscpy);
#endif

-/**
- * strscpy_pad() - Copy a C-string into a sized buffer
- * @dest: Where to copy the string to
- * @src: Where to copy the string from
- * @count: Size of destination buffer
- *
- * Copy the string, or as much of it as fits, into the dest buffer. The
- * behavior is undefined if the string buffers overlap. The destination
- * buffer is always %NUL terminated, unless it's zero-sized.
- *
- * If the source string is shorter than the destination buffer, zeros
- * the tail of the destination buffer.
- *
- * For full explanation of why you may want to consider using the
- * 'strscpy' functions please see the function docstring for strscpy().
- *
- * Returns:
- * * The number of characters copied (not including the trailing %NUL)
- * * -E2BIG if count is 0 or @src was truncated.
- */
-ssize_t strscpy_pad(char *dest, const char *src, size_t count)
-{
- ssize_t written;
-
- written = strscpy(dest, src, count);
- if (written < 0 || written == count - 1)
- return written;
-
- memset(dest + written + 1, 0, count - written - 1);
-
- return written;
-}
-EXPORT_SYMBOL(strscpy_pad);
-
/**
* stpcpy - copy a string from src to dest returning a pointer to the new end
* of dest, including src's %NUL-terminator. May overrun dest.
@@ -530,46 +491,6 @@ char *strnchr(const char *s, size_t count, int c)
EXPORT_SYMBOL(strnchr);
#endif

-/**
- * skip_spaces - Removes leading whitespace from @str.
- * @str: The string to be stripped.
- *
- * Returns a pointer to the first non-whitespace character in @str.
- */
-char *skip_spaces(const char *str)
-{
- while (isspace(*str))
- ++str;
- return (char *)str;
-}
-EXPORT_SYMBOL(skip_spaces);
-
-/**
- * strim - Removes leading and trailing whitespace from @s.
- * @s: The string to be stripped.
- *
- * Note that the first trailing whitespace is replaced with a %NUL-terminator
- * in the given string @s. Returns a pointer to the first non-whitespace
- * character in @s.
- */
-char *strim(char *s)
-{
- size_t size;
- char *end;
-
- size = strlen(s);
- if (!size)
- return s;
-
- end = s + size - 1;
- while (end >= s && isspace(*end))
- end--;
- *(end + 1) = '\0';
-
- return skip_spaces(s);
-}
-EXPORT_SYMBOL(strim);
-
#ifndef __HAVE_ARCH_STRLEN
/**
* strlen - Find the length of a string
@@ -704,101 +625,6 @@ char *strsep(char **s, const char *ct)
EXPORT_SYMBOL(strsep);
#endif

-/**
- * sysfs_streq - return true if strings are equal, modulo trailing newline
- * @s1: one string
- * @s2: another string
- *
- * This routine returns true iff two strings are equal, treating both
- * NUL and newline-then-NUL as equivalent string terminations. It's
- * geared for use with sysfs input strings, which generally terminate
- * with newlines but are compared against values without newlines.
- */
-bool sysfs_streq(const char *s1, const char *s2)
-{
- while (*s1 && *s1 == *s2) {
- s1++;
- s2++;
- }
-
- if (*s1 == *s2)
- return true;
- if (!*s1 && *s2 == '\n' && !s2[1])
- return true;
- if (*s1 == '\n' && !s1[1] && !*s2)
- return true;
- return false;
-}
-EXPORT_SYMBOL(sysfs_streq);
-
-/**
- * match_string - matches given string in an array
- * @array: array of strings
- * @n: number of strings in the array or -1 for NULL terminated arrays
- * @string: string to match with
- *
- * This routine will look for a string in an array of strings up to the
- * n-th element in the array or until the first NULL element.
- *
- * Historically the value of -1 for @n, was used to search in arrays that
- * are NULL terminated. However, the function does not make a distinction
- * when finishing the search: either @n elements have been compared OR
- * the first NULL element was found.
- *
- * Return:
- * index of a @string in the @array if matches, or %-EINVAL otherwise.
- */
-int match_string(const char * const *array, size_t n, const char *string)
-{
- int index;
- const char *item;
-
- for (index = 0; index < n; index++) {
- item = array[index];
- if (!item)
- break;
- if (!strcmp(item, string))
- return index;
- }
-
- return -EINVAL;
-}
-EXPORT_SYMBOL(match_string);
-
-/**
- * __sysfs_match_string - matches given string in an array
- * @array: array of strings
- * @n: number of strings in the array or -1 for NULL terminated arrays
- * @str: string to match with
- *
- * Returns index of @str in the @array or -EINVAL, just like match_string().
- * Uses sysfs_streq instead of strcmp for matching.
- *
- * This routine will look for a string in an array of strings up to the
- * n-th element in the array or until the first NULL element.
- *
- * Historically the value of -1 for @n, was used to search in arrays that
- * are NULL terminated. However, the function does not make a distinction
- * when finishing the search: either @n elements have been compared OR
- * the first NULL element was found.
- */
-int __sysfs_match_string(const char * const *array, size_t n, const char *str)
-{
- const char *item;
- int index;
-
- for (index = 0; index < n; index++) {
- item = array[index];
- if (!item)
- break;
- if (sysfs_streq(item, str))
- return index;
- }
-
- return -EINVAL;
-}
-EXPORT_SYMBOL(__sysfs_match_string);
-
#ifndef __HAVE_ARCH_MEMSET
/**
* memset - Fill a region of memory with the given value
@@ -1221,27 +1047,3 @@ void *memchr_inv(const void *start, int c, size_t bytes)
return check_bytes8(start, value, bytes % 8);
}
EXPORT_SYMBOL(memchr_inv);
-
-/**
- * strreplace - Replace all occurrences of character in string.
- * @s: The string to operate on.
- * @old: The character being replaced.
- * @new: The character @old is replaced with.
- *
- * Returns pointer to the nul byte at the end of @s.
- */
-char *strreplace(char *s, char old, char new)
-{
- for (; *s; ++s)
- if (*s == old)
- *s = new;
- return s;
-}
-EXPORT_SYMBOL(strreplace);
-
-void fortify_panic(const char *name)
-{
- pr_emerg("detected buffer overflow in %s\n", name);
- BUG();
-}
-EXPORT_SYMBOL(fortify_panic);
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 3806a52ce697..bde13612c25d 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -696,3 +696,196 @@ void kfree_strarray(char **array, size_t n)
kfree(array);
}
EXPORT_SYMBOL_GPL(kfree_strarray);
+
+/**
+ * strscpy_pad() - Copy a C-string into a sized buffer
+ * @dest: Where to copy the string to
+ * @src: Where to copy the string from
+ * @count: Size of destination buffer
+ *
+ * Copy the string, or as much of it as fits, into the dest buffer. The
+ * behavior is undefined if the string buffers overlap. The destination
+ * buffer is always %NUL terminated, unless it's zero-sized.
+ *
+ * If the source string is shorter than the destination buffer, zeros
+ * the tail of the destination buffer.
+ *
+ * For full explanation of why you may want to consider using the
+ * 'strscpy' functions please see the function docstring for strscpy().
+ *
+ * Returns:
+ * * The number of characters copied (not including the trailing %NUL)
+ * * -E2BIG if count is 0 or @src was truncated.
+ */
+ssize_t strscpy_pad(char *dest, const char *src, size_t count)
+{
+ ssize_t written;
+
+ written = strscpy(dest, src, count);
+ if (written < 0 || written == count - 1)
+ return written;
+
+ memset(dest + written + 1, 0, count - written - 1);
+
+ return written;
+}
+EXPORT_SYMBOL(strscpy_pad);
+
+/**
+ * skip_spaces - Removes leading whitespace from @str.
+ * @str: The string to be stripped.
+ *
+ * Returns a pointer to the first non-whitespace character in @str.
+ */
+char *skip_spaces(const char *str)
+{
+ while (isspace(*str))
+ ++str;
+ return (char *)str;
+}
+EXPORT_SYMBOL(skip_spaces);
+
+/**
+ * strim - Removes leading and trailing whitespace from @s.
+ * @s: The string to be stripped.
+ *
+ * Note that the first trailing whitespace is replaced with a %NUL-terminator
+ * in the given string @s. Returns a pointer to the first non-whitespace
+ * character in @s.
+ */
+char *strim(char *s)
+{
+ size_t size;
+ char *end;
+
+ size = strlen(s);
+ if (!size)
+ return s;
+
+ end = s + size - 1;
+ while (end >= s && isspace(*end))
+ end--;
+ *(end + 1) = '\0';
+
+ return skip_spaces(s);
+}
+EXPORT_SYMBOL(strim);
+
+/**
+ * sysfs_streq - return true if strings are equal, modulo trailing newline
+ * @s1: one string
+ * @s2: another string
+ *
+ * This routine returns true iff two strings are equal, treating both
+ * NUL and newline-then-NUL as equivalent string terminations. It's
+ * geared for use with sysfs input strings, which generally terminate
+ * with newlines but are compared against values without newlines.
+ */
+bool sysfs_streq(const char *s1, const char *s2)
+{
+ while (*s1 && *s1 == *s2) {
+ s1++;
+ s2++;
+ }
+
+ if (*s1 == *s2)
+ return true;
+ if (!*s1 && *s2 == '\n' && !s2[1])
+ return true;
+ if (*s1 == '\n' && !s1[1] && !*s2)
+ return true;
+ return false;
+}
+EXPORT_SYMBOL(sysfs_streq);
+
+/**
+ * match_string - matches given string in an array
+ * @array: array of strings
+ * @n: number of strings in the array or -1 for NULL terminated arrays
+ * @string: string to match with
+ *
+ * This routine will look for a string in an array of strings up to the
+ * n-th element in the array or until the first NULL element.
+ *
+ * Historically the value of -1 for @n, was used to search in arrays that
+ * are NULL terminated. However, the function does not make a distinction
+ * when finishing the search: either @n elements have been compared OR
+ * the first NULL element was found.
+ *
+ * Return:
+ * index of a @string in the @array if matches, or %-EINVAL otherwise.
+ */
+int match_string(const char * const *array, size_t n, const char *string)
+{
+ int index;
+ const char *item;
+
+ for (index = 0; index < n; index++) {
+ item = array[index];
+ if (!item)
+ break;
+ if (!strcmp(item, string))
+ return index;
+ }
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL(match_string);
+
+/**
+ * __sysfs_match_string - matches given string in an array
+ * @array: array of strings
+ * @n: number of strings in the array or -1 for NULL terminated arrays
+ * @str: string to match with
+ *
+ * Returns index of @str in the @array or -EINVAL, just like match_string().
+ * Uses sysfs_streq instead of strcmp for matching.
+ *
+ * This routine will look for a string in an array of strings up to the
+ * n-th element in the array or until the first NULL element.
+ *
+ * Historically the value of -1 for @n, was used to search in arrays that
+ * are NULL terminated. However, the function does not make a distinction
+ * when finishing the search: either @n elements have been compared OR
+ * the first NULL element was found.
+ */
+int __sysfs_match_string(const char * const *array, size_t n, const char *str)
+{
+ const char *item;
+ int index;
+
+ for (index = 0; index < n; index++) {
+ item = array[index];
+ if (!item)
+ break;
+ if (sysfs_streq(item, str))
+ return index;
+ }
+
+ return -EINVAL;
+}
+EXPORT_SYMBOL(__sysfs_match_string);
+
+/**
+ * strreplace - Replace all occurrences of character in string.
+ * @s: The string to operate on.
+ * @old: The character being replaced.
+ * @new: The character @old is replaced with.
+ *
+ * Returns pointer to the nul byte at the end of @s.
+ */
+char *strreplace(char *s, char old, char new)
+{
+ for (; *s; ++s)
+ if (*s == old)
+ *s = new;
+ return s;
+}
+EXPORT_SYMBOL(strreplace);
+
+void fortify_panic(const char *name)
+{
+ pr_emerg("detected buffer overflow in %s\n", name);
+ BUG();
+}
+EXPORT_SYMBOL(fortify_panic);
--
2.30.2