summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorKees Cook <keescook@chromium.org>2023-09-20 22:38:14 +0300
committerKees Cook <keescook@chromium.org>2024-02-21 07:47:32 +0300
commite6584c3964f2ff76a9fb5a701e4a59997b35e547 (patch)
tree330e893f5b937e2c335c08475a59df545b75f9e7
parentf478898e0aa74a759fcf629a3ee8b040467b8533 (diff)
downloadlinux-e6584c3964f2ff76a9fb5a701e4a59997b35e547.tar.xz
string: Allow 2-argument strscpy()
Using sizeof(dst) for the "size" argument in strscpy() is the overwhelmingly common case. Instead of requiring this everywhere, allow a 2-argument version to be used that will use the sizeof() internally. There are other functions in the kernel with optional arguments[1], so this isn't unprecedented, and improves readability. Update and relocate the kern-doc for strscpy() too, and drop __HAVE_ARCH_STRSCPY as it is unused. Adjust ARCH=um build to notice the changed export name, as it doesn't do full header includes for the string helpers. This could additionally let us save a few hundred lines of code: 1177 files changed, 2455 insertions(+), 3026 deletions(-) with a treewide cleanup using Coccinelle: @needless_arg@ expression DST, SRC; @@ strscpy(DST, SRC -, sizeof(DST) ) Link: https://elixir.bootlin.com/linux/v6.7/source/include/linux/pci.h#L1517 [1] Reviewed-by: Justin Stitt <justinstitt@google.com> Cc: Andy Shevchenko <andy@kernel.org> Cc: linux-hardening@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org>
-rw-r--r--arch/um/include/shared/user.h3
-rw-r--r--include/linux/fortify-string.h22
-rw-r--r--include/linux/string.h38
-rw-r--r--lib/string.c6
4 files changed, 41 insertions, 28 deletions
diff --git a/arch/um/include/shared/user.h b/arch/um/include/shared/user.h
index 981e11d8e025..9568cc04cbb7 100644
--- a/arch/um/include/shared/user.h
+++ b/arch/um/include/shared/user.h
@@ -51,7 +51,8 @@ static inline int printk(const char *fmt, ...)
extern int in_aton(char *str);
extern size_t strlcat(char *, const char *, size_t);
-extern size_t strscpy(char *, const char *, size_t);
+extern size_t sized_strscpy(char *, const char *, size_t);
+#define strscpy(dst, src, size) sized_strscpy(dst, src, size)
/* Copied from linux/compiler-gcc.h since we can't include it directly */
#define barrier() __asm__ __volatile__("": : :"memory")
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 89a6888f2f9e..06b3aaa63724 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -215,26 +215,8 @@ __kernel_size_t __fortify_strlen(const char * const POS p)
}
/* Defined after fortified strnlen() to reuse it. */
-extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy);
-/**
- * strscpy - Copy a C-string into a sized buffer
- *
- * @p: Where to copy the string to
- * @q: Where to copy the string from
- * @size: Size of destination buffer
- *
- * Copy the source string @q, or as much of it as fits, into the destination
- * @p buffer. The behavior is undefined if the string buffers overlap. The
- * destination @p buffer is always NUL terminated, unless it's zero-sized.
- *
- * Preferred to strncpy() since it always returns a valid string, and
- * doesn't unnecessarily force the tail of the destination buffer to be
- * zero padded. If padding is desired please use strscpy_pad().
- *
- * Returns the number of characters copied in @p (not including the
- * trailing %NUL) or -E2BIG if @size is 0 or the copy of @q was truncated.
- */
-__FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, size_t size)
+extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(sized_strscpy);
+__FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const POS q, size_t size)
{
/* Use string size rather than possible enclosing struct size. */
const size_t p_size = __member_size(p);
diff --git a/include/linux/string.h b/include/linux/string.h
index 78b28004c5ba..0d66bf9407fd 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -2,6 +2,7 @@
#ifndef _LINUX_STRING_H_
#define _LINUX_STRING_H_
+#include <linux/args.h>
#include <linux/array_size.h>
#include <linux/compiler.h> /* for inline */
#include <linux/types.h> /* for size_t */
@@ -66,9 +67,40 @@ extern char * strcpy(char *,const char *);
#ifndef __HAVE_ARCH_STRNCPY
extern char * strncpy(char *,const char *, __kernel_size_t);
#endif
-#ifndef __HAVE_ARCH_STRSCPY
-ssize_t strscpy(char *, const char *, size_t);
-#endif
+ssize_t sized_strscpy(char *, const char *, size_t);
+
+/*
+ * The 2 argument style can only be used when dst is an array with a
+ * known size.
+ */
+#define __strscpy0(dst, src, ...) \
+ sized_strscpy(dst, src, sizeof(dst) + __must_be_array(dst))
+#define __strscpy1(dst, src, size) sized_strscpy(dst, src, size)
+
+/**
+ * strscpy - Copy a C-string into a sized buffer
+ * @dst: Where to copy the string to
+ * @src: Where to copy the string from
+ * @...: Size of destination buffer (optional)
+ *
+ * Copy the source string @src, or as much of it as fits, into the
+ * destination @dst buffer. The behavior is undefined if the string
+ * buffers overlap. The destination @dst buffer is always NUL terminated,
+ * unless it's zero-sized.
+ *
+ * The size argument @... is only required when @dst is not an array, or
+ * when the copy needs to be smaller than sizeof(@dst).
+ *
+ * Preferred to strncpy() since it always returns a valid string, and
+ * doesn't unnecessarily force the tail of the destination buffer to be
+ * zero padded. If padding is desired please use strscpy_pad().
+ *
+ * Returns the number of characters copied in @dst (not including the
+ * trailing %NUL) or -E2BIG if @size is 0 or the copy from @src was
+ * truncated.
+ */
+#define strscpy(dst, src, ...) \
+ CONCATENATE(__strscpy, COUNT_ARGS(__VA_ARGS__))(dst, src, __VA_ARGS__)
/**
* strscpy_pad() - Copy a C-string into a sized buffer
diff --git a/lib/string.c b/lib/string.c
index f791559102f6..966da44bfc86 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -104,8 +104,7 @@ char *strncpy(char *dest, const char *src, size_t count)
EXPORT_SYMBOL(strncpy);
#endif
-#ifndef __HAVE_ARCH_STRSCPY
-ssize_t strscpy(char *dest, const char *src, size_t count)
+ssize_t sized_strscpy(char *dest, const char *src, size_t count)
{
const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
size_t max = count;
@@ -171,8 +170,7 @@ ssize_t strscpy(char *dest, const char *src, size_t count)
return -E2BIG;
}
-EXPORT_SYMBOL(strscpy);
-#endif
+EXPORT_SYMBOL(sized_strscpy);
/**
* stpcpy - copy a string from src to dest returning a pointer to the new end