hardening fixes for v6.11-rc4

- gcc-plugins: randstruct: Remove GCC 4.7 or newer requirement
   (Thorsten Blum)
 
 - kallsyms: Clean up interaction with LTO suffixes (Song Liu)
 
 - refcount: Report UAF for refcount_sub_and_test(0) when counter==0
   (Petr Pavlu)
 
 - kunit/overflow: Avoid misallocation of driver name (Ivan Orlov)
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Merge tag 'hardening-v6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull hardening fixes from Kees Cook:

 - gcc-plugins: randstruct: Remove GCC 4.7 or newer requirement
   (Thorsten Blum)

 - kallsyms: Clean up interaction with LTO suffixes (Song Liu)

 - refcount: Report UAF for refcount_sub_and_test(0) when counter==0
   (Petr Pavlu)

 - kunit/overflow: Avoid misallocation of driver name (Ivan Orlov)

* tag 'hardening-v6.11-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  kallsyms: Match symbols exactly with CONFIG_LTO_CLANG
  kallsyms: Do not cleanup .llvm.<hash> suffix before sorting symbols
  kunit/overflow: Fix UB in overflow_allocation_test
  gcc-plugins: randstruct: Remove GCC 4.7 or newer requirement
  refcount: Report UAF for refcount_sub_and_test(0) when counter==0

drivers/misc/lkdtm/refcount.c

@@ -182,6 +182,21 @@ static void lkdtm_REFCOUNT_SUB_AND_TEST_NEGATIVE(void)
 	check_negative(&neg, 3);
 }
 
+/*
+ * A refcount_sub_and_test() by zero when the counter is at zero should act like
+ * refcount_sub_and_test() above when going negative.
+ */
+static void lkdtm_REFCOUNT_SUB_AND_TEST_ZERO(void)
+{
+	refcount_t neg = REFCOUNT_INIT(0);
+
+	pr_info("attempting bad refcount_sub_and_test() at zero\n");
+	if (refcount_sub_and_test(0, &neg))
+		pr_warn("Weird: refcount_sub_and_test() reported zero\n");
+
+	check_negative(&neg, 0);
+}
+
 static void check_from_zero(refcount_t *ref)
 {
 	switch (refcount_read(ref)) {
@@ -400,6 +415,7 @@ static struct crashtype crashtypes[] = {
 	CRASHTYPE(REFCOUNT_DEC_NEGATIVE),
 	CRASHTYPE(REFCOUNT_DEC_AND_TEST_NEGATIVE),
 	CRASHTYPE(REFCOUNT_SUB_AND_TEST_NEGATIVE),
+	CRASHTYPE(REFCOUNT_SUB_AND_TEST_ZERO),
 	CRASHTYPE(REFCOUNT_INC_ZERO),
 	CRASHTYPE(REFCOUNT_ADD_ZERO),
 	CRASHTYPE(REFCOUNT_INC_SATURATED),

include/linux/refcount.h

@@ -266,12 +266,12 @@ bool __refcount_sub_and_test(int i, refcount_t *r, int *oldp)
 	if (oldp)
 		*oldp = old;
 
-	if (old == i) {
+	if (old > 0 && old == i) {
 		smp_acquire__after_ctrl_dep();
 		return true;
 	}
 
-	if (unlikely(old < 0 || old - i < 0))
+	if (unlikely(old <= 0 || old - i < 0))
 		refcount_warn_saturate(r, REFCOUNT_SUB_UAF);
 
 	return false;

kernel/kallsyms.c

@@ -160,38 +160,6 @@ unsigned long kallsyms_sym_address(int idx)
 	return kallsyms_relative_base - 1 - kallsyms_offsets[idx];
 }
 
-static void cleanup_symbol_name(char *s)
-{
-	char *res;
-
-	if (!IS_ENABLED(CONFIG_LTO_CLANG))
-		return;
-
-	/*
-	 * LLVM appends various suffixes for local functions and variables that
-	 * must be promoted to global scope as part of LTO.  This can break
-	 * hooking of static functions with kprobes. '.' is not a valid
-	 * character in an identifier in C. Suffixes only in LLVM LTO observed:
-	 * - foo.llvm.[0-9a-f]+
-	 */
-	res = strstr(s, ".llvm.");
-	if (res)
-		*res = '\0';
-
-	return;
-}
-
-static int compare_symbol_name(const char *name, char *namebuf)
-{
-	/* The kallsyms_seqs_of_names is sorted based on names after
-	 * cleanup_symbol_name() (see scripts/kallsyms.c) if clang lto is enabled.
-	 * To ensure correct bisection in kallsyms_lookup_names(), do
-	 * cleanup_symbol_name(namebuf) before comparing name and namebuf.
-	 */
-	cleanup_symbol_name(namebuf);
-	return strcmp(name, namebuf);
-}
-
 static unsigned int get_symbol_seq(int index)
 {
 	unsigned int i, seq = 0;
@@ -219,7 +187,7 @@ static int kallsyms_lookup_names(const char *name,
 		seq = get_symbol_seq(mid);
 		off = get_symbol_offset(seq);
 		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
-		ret = compare_symbol_name(name, namebuf);
+		ret = strcmp(name, namebuf);
 		if (ret > 0)
 			low = mid + 1;
 		else if (ret < 0)
@@ -236,7 +204,7 @@ static int kallsyms_lookup_names(const char *name,
 		seq = get_symbol_seq(low - 1);
 		off = get_symbol_offset(seq);
 		kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
-		if (compare_symbol_name(name, namebuf))
+		if (strcmp(name, namebuf))
 			break;
 		low--;
 	}
@@ -248,7 +216,7 @@ static int kallsyms_lookup_names(const char *name,
 			seq = get_symbol_seq(high + 1);
 			off = get_symbol_offset(seq);
 			kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
-			if (compare_symbol_name(name, namebuf))
+			if (strcmp(name, namebuf))
 				break;
 			high++;
 		}
@@ -407,8 +375,7 @@ static int kallsyms_lookup_buildid(unsigned long addr,
 		if (modbuildid)
 			*modbuildid = NULL;
 
-		ret = strlen(namebuf);
+		return strlen(namebuf);
-		goto found;
 	}
 
 	/* See if it's in a module or a BPF JITed image. */
@@ -422,8 +389,6 @@ static int kallsyms_lookup_buildid(unsigned long addr,
 		ret = ftrace_mod_address_lookup(addr, symbolsize,
 						offset, modname, namebuf);
 
-found:
-	cleanup_symbol_name(namebuf);
 	return ret;
 }
 
@@ -450,8 +415,6 @@ const char *kallsyms_lookup(unsigned long addr,
 
 int lookup_symbol_name(unsigned long addr, char *symname)
 {
-	int res;
-
 	symname[0] = '\0';
 	symname[KSYM_NAME_LEN - 1] = '\0';
 
@@ -462,16 +425,10 @@ int lookup_symbol_name(unsigned long addr, char *symname)
 		/* Grab name */
 		kallsyms_expand_symbol(get_symbol_offset(pos),
 				       symname, KSYM_NAME_LEN);
-		goto found;
+		return 0;
 	}
 	/* See if it's in a module. */
-	res = lookup_module_symbol_name(addr, symname);
+	return lookup_module_symbol_name(addr, symname);
-	if (res)
-		return res;
-
-found:
-	cleanup_symbol_name(symname);
-	return 0;
 }
 
 /* Look up a kernel symbol and return it in a text buffer. */

kernel/kallsyms_selftest.c

@@ -187,31 +187,11 @@ static void test_perf_kallsyms_lookup_name(void)
 		stat.min, stat.max, div_u64(stat.sum, stat.real_cnt));
 }
 
-static bool match_cleanup_name(const char *s, const char *name)
-{
-	char *p;
-	int len;
-
-	if (!IS_ENABLED(CONFIG_LTO_CLANG))
-		return false;
-
-	p = strstr(s, ".llvm.");
-	if (!p)
-		return false;
-
-	len = strlen(name);
-	if (p - s != len)
-		return false;
-
-	return !strncmp(s, name, len);
-}
-
 static int find_symbol(void *data, const char *name, unsigned long addr)
 {
 	struct test_stat *stat = (struct test_stat *)data;
 
-	if (strcmp(name, stat->name) == 0 ||
+	if (!strcmp(name, stat->name)) {
-	    (!stat->perf && match_cleanup_name(name, stat->name))) {
 		stat->real_cnt++;
 		stat->addr = addr;
 

lib/overflow_kunit.c

@@ -668,7 +668,6 @@ DEFINE_TEST_ALLOC(devm_kzalloc,  devm_kfree, 1, 1, 0);
 
 static void overflow_allocation_test(struct kunit *test)
 {
-	const char device_name[] = "overflow-test";
 	struct device *dev;
 	int count = 0;
 
@@ -678,7 +677,7 @@ static void overflow_allocation_test(struct kunit *test)
 } while (0)
 
 	/* Create dummy device for devm_kmalloc()-family tests. */
-	dev = kunit_device_register(test, device_name);
+	dev = kunit_device_register(test, "overflow-test");
 	KUNIT_ASSERT_FALSE_MSG(test, IS_ERR(dev),
 			       "Cannot register test device\n");
 

scripts/gcc-plugins/randomize_layout_plugin.c

@@ -19,10 +19,6 @@
 #include "gcc-common.h"
 #include "randomize_layout_seed.h"
 
-#if BUILDING_GCC_MAJOR < 4 || (BUILDING_GCC_MAJOR == 4 && BUILDING_GCC_MINOR < 7)
-#error "The RANDSTRUCT plugin requires GCC 4.7 or newer."
-#endif
-
 #define ORIG_TYPE_NAME(node) \
 	(TYPE_NAME(TYPE_MAIN_VARIANT(node)) != NULL_TREE ? ((const unsigned char *)IDENTIFIER_POINTER(TYPE_NAME(TYPE_MAIN_VARIANT(node)))) : (const unsigned char *)"anonymous")
 

scripts/kallsyms.c

@@ -5,8 +5,7 @@
  * This software may be used and distributed according to the terms
  * of the GNU General Public License, incorporated herein by reference.
  *
- * Usage: kallsyms [--all-symbols] [--absolute-percpu]
+ * Usage: kallsyms [--all-symbols] [--absolute-percpu]  in.map > out.S
- *                         [--lto-clang] in.map > out.S
  *
  *      Table compression uses all the unused char codes on the symbols and
  *  maps these to the most used substrings (tokens). For instance, it might
@@ -62,7 +61,6 @@ static struct sym_entry **table;
 static unsigned int table_size, table_cnt;
 static int all_symbols;
 static int absolute_percpu;
-static int lto_clang;
 
 static int token_profit[0x10000];
 
@@ -73,8 +71,7 @@ static unsigned char best_table_len[256];
 
 static void usage(void)
 {
-	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] "
+	fprintf(stderr, "Usage: kallsyms [--all-symbols] [--absolute-percpu] in.map > out.S\n");
-			"[--lto-clang] in.map > out.S\n");
 	exit(1);
 }
 
@@ -344,25 +341,6 @@ static bool symbol_absolute(const struct sym_entry *s)
 	return s->percpu_absolute;
 }
 
-static void cleanup_symbol_name(char *s)
-{
-	char *p;
-
-	/*
-	 * ASCII[.]   = 2e
-	 * ASCII[0-9] = 30,39
-	 * ASCII[A-Z] = 41,5a
-	 * ASCII[_]   = 5f
-	 * ASCII[a-z] = 61,7a
-	 *
-	 * As above, replacing the first '.' in ".llvm." with '\0' does not
-	 * affect the main sorting, but it helps us with subsorting.
-	 */
-	p = strstr(s, ".llvm.");
-	if (p)
-		*p = '\0';
-}
-
 static int compare_names(const void *a, const void *b)
 {
 	int ret;
@@ -526,10 +504,6 @@ static void write_src(void)
 	output_address(relative_base);
 	printf("\n");
 
-	if (lto_clang)
-		for (i = 0; i < table_cnt; i++)
-			cleanup_symbol_name((char *)table[i]->sym);
-
 	sort_symbols_by_name();
 	output_label("kallsyms_seqs_of_names");
 	for (i = 0; i < table_cnt; i++)
@@ -807,7 +781,6 @@ int main(int argc, char **argv)
 		static const struct option long_options[] = {
 			{"all-symbols",     no_argument, &all_symbols,     1},
 			{"absolute-percpu", no_argument, &absolute_percpu, 1},
-			{"lto-clang",       no_argument, &lto_clang,       1},
 			{},
 		};
 

scripts/link-vmlinux.sh

@@ -156,10 +156,6 @@ kallsyms()
 		kallsymopt="${kallsymopt} --absolute-percpu"
 	fi
 
-	if is_enabled CONFIG_LTO_CLANG; then
-		kallsymopt="${kallsymopt} --lto-clang"
-	fi
-
 	info KSYMS "${2}.S"
 	scripts/kallsyms ${kallsymopt} "${1}" > "${2}.S"