On Sun, Aug 22, 2021 at 12:51 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
> 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
Sorry, is there more info on what exactly __NO_FORTIFY is (and why we
"need" it)?
> 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.
>
> Acked-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
> 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"
^ should we just `#define __NO_FORTIFY` here in pgtable_64.c rather
than set that for a whole header?
> #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 77bd0b1d3296..1e6259f263b8 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@xxxxxxxxxxxxxxxxxxxxxxxxx>
> - * - 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@xxxxxxxxxxxx>,
> - * Matthew Hawkins <matt@xxxxxxxxxxxxxxxxx>
> - * - 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>
> @@ -237,40 +232,6 @@ 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.
> @@ -513,46 +474,6 @@ 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
> @@ -687,101 +608,6 @@ 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);
> -
are memset16, memset32, and memset64 worth moving as well? Also,
memscan(), check_bytes(), memchr_inv()?
> #ifndef __HAVE_ARCH_MEMSET
> /**
> * memset - Fill a region of memory with the given value
> @@ -1125,27 +951,3 @@ 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 5a35c7e16e96..e9433caab217 100644
> --- a/lib/string_helpers.c
> +++ b/lib/string_helpers.c
> @@ -692,3 +692,196 @@ 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);
> --
--
Thanks,
~Nick Desaulniers
