Merge tag 'hardening-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull hardening updates from Kees Cook:
 "There are three areas of note:

  A bunch of strlcpy()->strscpy() conversions ended up living in my tree
  since they were either Acked by maintainers for me to carry, or got
  ignored for multiple weeks (and were trivial changes).

  The compiler option '-fstrict-flex-arrays=3' has been enabled
  globally, and has been in -next for the entire devel cycle. This
  changes compiler diagnostics (though mainly just -Warray-bounds which
  is disabled) and potential UBSAN_BOUNDS and FORTIFY _warning_
  coverage. In other words, there are no new restrictions, just
  potentially new warnings. Any new FORTIFY warnings we've seen have
  been fixed (usually in their respective subsystem trees). For more
  details, see commit df8fc4e934c12b.

  The under-development compiler attribute __counted_by has been added
  so that we can start annotating flexible array members with their
  associated structure member that tracks the count of flexible array
  elements at run-time. It is possible (likely?) that the exact syntax
  of the attribute will change before it is finalized, but GCC and Clang
  are working together to sort it out. Any changes can be made to the
  macro while we continue to add annotations.

  As an example of that last case, I have a treewide commit waiting with
  such annotations found via Coccinelle:

    https://git.kernel.org/linus/adc5b3cb48a049563dc673f348eab7b6beba8a9b

  Also see commit dd06e72e68bcb4 for more details.

  Summary:

   - Fix KMSAN vs FORTIFY in strlcpy/strlcat (Alexander Potapenko)

   - Convert strreplace() to return string start (Andy Shevchenko)

   - Flexible array conversions (Arnd Bergmann, Wyes Karny, Kees Cook)

   - Add missing function prototypes seen with W=1 (Arnd Bergmann)

   - Fix strscpy() kerndoc typo (Arne Welzel)

   - Replace strlcpy() with strscpy() across many subsystems which were
     either Acked by respective maintainers or were trivial changes that
     went ignored for multiple weeks (Azeem Shaikh)

   - Remove unneeded cc-option test for UBSAN_TRAP (Nick Desaulniers)

   - Add KUnit tests for strcat()-family

   - Enable KUnit tests of FORTIFY wrappers under UML

   - Add more complete FORTIFY protections for strlcat()

   - Add missed disabling of FORTIFY for all arch purgatories.

   - Enable -fstrict-flex-arrays=3 globally

   - Tightening UBSAN_BOUNDS when using GCC

   - Improve checkpatch to check for strcpy, strncpy, and fake flex
     arrays

   - Improve use of const variables in FORTIFY

   - Add requested struct_size_t() helper for types not pointers

   - Add __counted_by macro for annotating flexible array size members"

* tag 'hardening-v6.5-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux: (54 commits)
  netfilter: ipset: Replace strlcpy with strscpy
  uml: Replace strlcpy with strscpy
  um: Use HOST_DIR for mrproper
  kallsyms: Replace all non-returning strlcpy with strscpy
  sh: Replace all non-returning strlcpy with strscpy
  of/flattree: Replace all non-returning strlcpy with strscpy
  sparc64: Replace all non-returning strlcpy with strscpy
  Hexagon: Replace all non-returning strlcpy with strscpy
  kobject: Use return value of strreplace()
  lib/string_helpers: Change returned value of the strreplace()
  jbd2: Avoid printing outside the boundary of the buffer
  checkpatch: Check for 0-length and 1-element arrays
  riscv/purgatory: Do not use fortified string functions
  s390/purgatory: Do not use fortified string functions
  x86/purgatory: Do not use fortified string functions
  acpi: Replace struct acpi_table_slit 1-element array with flex-array
  clocksource: Replace all non-returning strlcpy with strscpy
  string: use __builtin_memcpy() in strlcpy/strlcat
  staging: most: Replace all non-returning strlcpy with strscpy
  drm/i2c: tda998x: Replace all non-returning strlcpy with strscpy
  ...

4 files changed, 143 insertions, 51 deletions

diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h
index 84864767a56a..571fa7924f74 100644
--- a/include/linux/compiler_attributes.h
+++ b/include/linux/compiler_attributes.h
@@ -124,6 +124,19 @@
 #endif
 
 /*
+ * Optional: only supported since gcc >= 14
+ * Optional: only supported since clang >= 17
+ *
+ *   gcc: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108896
+ * clang: https://reviews.llvm.org/D148381
+ */
+#if __has_attribute(__element_count__)
+# define __counted_by(member)		__attribute__((__element_count__(#member)))
+#else
+# define __counted_by(member)
+#endif
+
+/*
  * Optional: only supported since clang >= 14.0
  *
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-error-function-attribute
diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index c9de1f59ee80..da51a83b2829 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -20,7 +20,7 @@ void __write_overflow_field(size_t avail, size_t wanted) __compiletime_warning("
 ({								\
 	char *__p = (char *)(p);				\
 	size_t __ret = SIZE_MAX;				\
-	size_t __p_size = __member_size(p);			\
+	const size_t __p_size = __member_size(p);		\
 	if (__p_size != SIZE_MAX &&				\
 	    __builtin_constant_p(*__p)) {			\
 		size_t __p_len = __p_size - 1;			\
@@ -142,7 +142,7 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size)
 __FORTIFY_INLINE __diagnose_as(__builtin_strncpy, 1, 2, 3)
 char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
 {
-	size_t p_size = __member_size(p);
+	const size_t p_size = __member_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__write_overflow();
@@ -151,33 +151,6 @@ char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
 	return __underlying_strncpy(p, q, size);
 }
 
-/**
- * strcat - Append a string to an existing string
- *
- * @p: pointer to NUL-terminated string to append to
- * @q: pointer to NUL-terminated source string to append from
- *
- * Do not use this function. While FORTIFY_SOURCE tries to avoid
- * read and write overflows, this is only possible when the
- * destination buffer size is known to the compiler. Prefer
- * building the string with formatting, via scnprintf() or similar.
- * At the very least, use strncat().
- *
- * Returns @p.
- *
- */
-__FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2)
-char *strcat(char * const POS p, const char *q)
-{
-	size_t p_size = __member_size(p);
-
-	if (p_size == SIZE_MAX)
-		return __underlying_strcat(p, q);
-	if (strlcat(p, q, p_size) >= p_size)
-		fortify_panic(__func__);
-	return p;
-}
-
 extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(strnlen);
 /**
  * strnlen - Return bounded count of characters in a NUL-terminated string
@@ -191,8 +164,8 @@ extern __kernel_size_t __real_strnlen(const char *, __kernel_size_t) __RENAME(st
  */
 __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size_t maxlen)
 {
-	size_t p_size = __member_size(p);
-	size_t p_len = __compiletime_strlen(p);
+	const size_t p_size = __member_size(p);
+	const size_t p_len = __compiletime_strlen(p);
 	size_t ret;
 
 	/* We can take compile-time actions when maxlen is const. */
@@ -233,8 +206,8 @@ __FORTIFY_INLINE __kernel_size_t strnlen(const char * const POS p, __kernel_size
 __FORTIFY_INLINE __diagnose_as(__builtin_strlen, 1)
 __kernel_size_t __fortify_strlen(const char * const POS p)
 {
+	const size_t p_size = __member_size(p);
 	__kernel_size_t ret;
-	size_t p_size = __member_size(p);
 
 	/* Give up if we don't know how large p is. */
 	if (p_size == SIZE_MAX)
@@ -267,8 +240,8 @@ extern size_t __real_strlcpy(char *, const char *, size_t) __RENAME(strlcpy);
  */
 __FORTIFY_INLINE size_t strlcpy(char * const POS p, const char * const POS q, size_t size)
 {
-	size_t p_size = __member_size(p);
-	size_t q_size = __member_size(q);
+	const size_t p_size = __member_size(p);
+	const size_t q_size = __member_size(q);
 	size_t q_len;	/* Full count of source string length. */
 	size_t len;	/* Count of characters going into destination. */
 
@@ -299,8 +272,8 @@ extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy);
  * @q: Where to copy the string from
  * @size: Size of destination buffer
  *
- * Copy the source string @p, or as much of it as fits, into the destination
- * @q buffer. The behavior is undefined if the string buffers overlap. The
+ * 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 strlcpy() since the API doesn't require reading memory
@@ -318,10 +291,10 @@ extern ssize_t __real_strscpy(char *, const char *, size_t) __RENAME(strscpy);
  */
 __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, size_t size)
 {
-	size_t len;
 	/* Use string size rather than possible enclosing struct size. */
-	size_t p_size = __member_size(p);
-	size_t q_size = __member_size(q);
+	const size_t p_size = __member_size(p);
+	const size_t q_size = __member_size(q);
+	size_t len;
 
 	/* If we cannot get size of p and q default to call strscpy. */
 	if (p_size == SIZE_MAX && q_size == SIZE_MAX)
@@ -371,6 +344,96 @@ __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, s
 	return __real_strscpy(p, q, len);
 }
 
+/* Defined after fortified strlen() to reuse it. */
+extern size_t __real_strlcat(char *p, const char *q, size_t avail) __RENAME(strlcat);
+/**
+ * strlcat - Append a string to an existing string
+ *
+ * @p: pointer to %NUL-terminated string to append to
+ * @q: pointer to %NUL-terminated string to append from
+ * @avail: Maximum bytes available in @p
+ *
+ * Appends %NUL-terminated string @q after the %NUL-terminated
+ * string at @p, but will not write beyond @avail bytes total,
+ * potentially truncating the copy from @q. @p will stay
+ * %NUL-terminated only if a %NUL already existed within
+ * the @avail bytes of @p. If so, the resulting number of
+ * bytes copied from @q will be at most "@avail - strlen(@p) - 1".
+ *
+ * Do not use this function. While FORTIFY_SOURCE tries to avoid
+ * read and write overflows, this is only possible when the sizes
+ * of @p and @q are known to the compiler. Prefer building the
+ * string with formatting, via scnprintf(), seq_buf, or similar.
+ *
+ * Returns total bytes that _would_ have been contained by @p
+ * regardless of truncation, similar to snprintf(). If return
+ * value is >= @avail, the string has been truncated.
+ *
+ */
+__FORTIFY_INLINE
+size_t strlcat(char * const POS p, const char * const POS q, size_t avail)
+{
+	const size_t p_size = __member_size(p);
+	const size_t q_size = __member_size(q);
+	size_t p_len, copy_len;
+	size_t actual, wanted;
+
+	/* Give up immediately if both buffer sizes are unknown. */
+	if (p_size == SIZE_MAX && q_size == SIZE_MAX)
+		return __real_strlcat(p, q, avail);
+
+	p_len = strnlen(p, avail);
+	copy_len = strlen(q);
+	wanted = actual = p_len + copy_len;
+
+	/* Cannot append any more: report truncation. */
+	if (avail <= p_len)
+		return wanted;
+
+	/* Give up if string is already overflowed. */
+	if (p_size <= p_len)
+		fortify_panic(__func__);
+
+	if (actual >= avail) {
+		copy_len = avail - p_len - 1;
+		actual = p_len + copy_len;
+	}
+
+	/* Give up if copy will overflow. */
+	if (p_size <= actual)
+		fortify_panic(__func__);
+	__underlying_memcpy(p + p_len, q, copy_len);
+	p[actual] = '\0';
+
+	return wanted;
+}
+
+/* Defined after fortified strlcat() to reuse it. */
+/**
+ * strcat - Append a string to an existing string
+ *
+ * @p: pointer to NUL-terminated string to append to
+ * @q: pointer to NUL-terminated source string to append from
+ *
+ * Do not use this function. While FORTIFY_SOURCE tries to avoid
+ * read and write overflows, this is only possible when the
+ * destination buffer size is known to the compiler. Prefer
+ * building the string with formatting, via scnprintf() or similar.
+ * At the very least, use strncat().
+ *
+ * Returns @p.
+ *
+ */
+__FORTIFY_INLINE __diagnose_as(__builtin_strcat, 1, 2)
+char *strcat(char * const POS p, const char *q)
+{
+	const size_t p_size = __member_size(p);
+
+	if (strlcat(p, q, p_size) >= p_size)
+		fortify_panic(__func__);
+	return p;
+}
+
 /**
  * strncat - Append a string to an existing string
  *
@@ -394,9 +457,9 @@ __FORTIFY_INLINE ssize_t strscpy(char * const POS p, const char * const POS q, s
 __FORTIFY_INLINE __diagnose_as(__builtin_strncat, 1, 2, 3)
 char *strncat(char * const POS p, const char * const POS q, __kernel_size_t count)
 {
+	const size_t p_size = __member_size(p);
+	const size_t q_size = __member_size(q);
 	size_t p_len, copy_len;
-	size_t p_size = __member_size(p);
-	size_t q_size = __member_size(q);
 
 	if (p_size == SIZE_MAX && q_size == SIZE_MAX)
 		return __underlying_strncat(p, q, count);
@@ -639,7 +702,7 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
 extern void *__real_memscan(void *, int, __kernel_size_t) __RENAME(memscan);
 __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
 {
-	size_t p_size = __struct_size(p);
+	const size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -651,8 +714,8 @@ __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
 __FORTIFY_INLINE __diagnose_as(__builtin_memcmp, 1, 2, 3)
 int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t size)
 {
-	size_t p_size = __struct_size(p);
-	size_t q_size = __struct_size(q);
+	const size_t p_size = __struct_size(p);
+	const size_t q_size = __struct_size(q);
 
 	if (__builtin_constant_p(size)) {
 		if (__compiletime_lessthan(p_size, size))
@@ -668,7 +731,7 @@ int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t
 __FORTIFY_INLINE __diagnose_as(__builtin_memchr, 1, 2, 3)
 void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
 {
-	size_t p_size = __struct_size(p);
+	const size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -680,7 +743,7 @@ void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
 void *__real_memchr_inv(const void *s, int c, size_t n) __RENAME(memchr_inv);
 __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
 {
-	size_t p_size = __struct_size(p);
+	const size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -693,7 +756,7 @@ extern void *__real_kmemdup(const void *src, size_t len, gfp_t gfp) __RENAME(kme
 								    __realloc_size(2);
 __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp)
 {
-	size_t p_size = __struct_size(p);
+	const size_t p_size = __struct_size(p);
 
 	if (__compiletime_lessthan(p_size, size))
 		__read_overflow();
@@ -720,8 +783,8 @@ __FORTIFY_INLINE void *kmemdup(const void * const POS0 p, size_t size, gfp_t gfp
 __FORTIFY_INLINE __diagnose_as(__builtin_strcpy, 1, 2)
 char *strcpy(char * const POS p, const char * const POS q)
 {
-	size_t p_size = __member_size(p);
-	size_t q_size = __member_size(q);
+	const size_t p_size = __member_size(p);
+	const size_t q_size = __member_size(q);
 	size_t size;
 
 	/* If neither buffer size is known, immediately give up. */
diff --git a/include/linux/overflow.h b/include/linux/overflow.h
index 0e33b5cbdb9f..f9b60313eaea 100644
--- a/include/linux/overflow.h
+++ b/include/linux/overflow.h
@@ -283,7 +283,7 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
  * @member: Name of the array member.
  * @count: Number of elements in the array.
  *
- * Calculates size of memory needed for structure @p followed by an
+ * Calculates size of memory needed for structure of @p followed by an
  * array of @count number of @member elements.
  *
  * Return: number of bytes needed or SIZE_MAX on overflow.
@@ -293,4 +293,20 @@ static inline size_t __must_check size_sub(size_t minuend, size_t subtrahend)
 		sizeof(*(p)) + flex_array_size(p, member, count),	\
 		size_add(sizeof(*(p)), flex_array_size(p, member, count)))
 
+/**
+ * struct_size_t() - Calculate size of structure with trailing flexible array
+ * @type: structure type name.
+ * @member: Name of the array member.
+ * @count: Number of elements in the array.
+ *
+ * Calculates size of memory needed for structure @type followed by an
+ * array of @count number of @member elements. Prefer using struct_size()
+ * when possible instead, to keep calculations associated with a specific
+ * instance variable of type @type.
+ *
+ * Return: number of bytes needed or SIZE_MAX on overflow.
+ */
+#define struct_size_t(type, member, count)					\
+	struct_size((type *)NULL, member, count)
+
 #endif /* __LINUX_OVERFLOW_H */
diff --git a/include/linux/string.h b/include/linux/string.h
index c062c581a98b..dbfc66400050 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -169,7 +169,7 @@ static inline void memcpy_flushcache(void *dst, const void *src, size_t cnt)
 #endif
 
 void *memchr_inv(const void *s, int c, size_t n);
-char *strreplace(char *s, char old, char new);
+char *strreplace(char *str, char old, char new);
 
 extern void kfree_const(const void *x);