3 files changed, 33 insertions, 64 deletions

diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 9c48ddad0f0d..1826c7407258 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -274,11 +274,6 @@ static bool escape_space(unsigned char c, char **dst, char *end)
                 return false;
         }
 
-        if (out + 2 > end) {
-                *dst = out + 2;
-                return true;
-        }
-
         if (out < end)
                 *out = '\\';
         ++out;
@@ -309,11 +304,6 @@ static bool escape_special(unsigned char c, char **dst, char *end)
                 return false;
         }
 
-        if (out + 2 > end) {
-                *dst = out + 2;
-                return true;
-        }
-
         if (out < end)
                 *out = '\\';
         ++out;
@@ -332,11 +322,6 @@ static bool escape_null(unsigned char c, char **dst, char *end)
         if (c)
                 return false;
 
-        if (out + 2 > end) {
-                *dst = out + 2;
-                return true;
-        }
-
         if (out < end)
                 *out = '\\';
         ++out;
@@ -352,11 +337,6 @@ static bool escape_octal(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
 
-        if (out + 4 > end) {
-                *dst = out + 4;
-                return true;
-        }
-
         if (out < end)
                 *out = '\\';
         ++out;
@@ -378,11 +358,6 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
 {
         char *out = *dst;
 
-        if (out + 4 > end) {
-                *dst = out + 4;
-                return true;
-        }
-
         if (out < end)
                 *out = '\\';
         ++out;
@@ -449,20 +424,17 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
  * it if needs.
  *
  * Return:
- * The amount of the characters processed to the destination buffer, or
- * %-ENOMEM if the size of buffer is not enough to put an escaped character is
- * returned.
- *
- * Even in the case of error @dst pointer will be updated to point to the byte
- * after the last processed character.
+ * The total size of the escaped output that would be generated for
+ * the given input and flags. To check whether the output was
+ * truncated, compare the return value to osz. There is room left in
+ * dst for a '\0' terminator if and only if ret < osz.
  */
-int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
+int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
                       unsigned int flags, const char *esc)
 {
-        char *p = *dst;
+        char *p = dst;
         char *end = p + osz;
         bool is_dict = esc && *esc;
-        int ret;
 
         while (isz--) {
                 unsigned char c = *src++;
@@ -502,13 +474,6 @@ int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
                 escape_passthrough(c, &p, end);
         }
 
-        if (p > end) {
-                *dst = end;
-                return -ENOMEM;
-        }
-
-        ret = p - *dst;
-        *dst = p;
-        return ret;
+        return p - dst;
 }
 EXPORT_SYMBOL(string_escape_mem);
diff --git a/lib/test-string_helpers.c b/lib/test-string_helpers.c
index ab0d30e1e18f..8e376efd88a4 100644
--- a/lib/test-string_helpers.c
+++ b/lib/test-string_helpers.c
@@ -260,16 +260,28 @@ static __init const char *test_string_find_match(const struct test_string_2 *s2,
         return NULL;
 }
 
+static __init void
+test_string_escape_overflow(const char *in, int p, unsigned int flags, const char *esc,
+                            int q_test, const char *name)
+{
+        int q_real;
+
+        q_real = string_escape_mem(in, p, NULL, 0, flags, esc);
+        if (q_real != q_test)
+                pr_warn("Test '%s' failed: flags = %u, osz = 0, expected %d, got %d\n",
+                        name, flags, q_test, q_real);
+}
+
 static __init void test_string_escape(const char *name,
                                       const struct test_string_2 *s2,
                                       unsigned int flags, const char *esc)
 {
-        int q_real = 512;
-        char *out_test = kmalloc(q_real, GFP_KERNEL);
-        char *out_real = kmalloc(q_real, GFP_KERNEL);
+        size_t out_size = 512;
+        char *out_test = kmalloc(out_size, GFP_KERNEL);
+        char *out_real = kmalloc(out_size, GFP_KERNEL);
         char *in = kmalloc(256, GFP_KERNEL);
-        char *buf = out_real;
         int p = 0, q_test = 0;
+        int q_real;
 
         if (!out_test || !out_real || !in)
                 goto out;
@@ -301,29 +313,19 @@ static __init void test_string_escape(const char *name,
                 q_test += len;
         }
 
-        q_real = string_escape_mem(in, p, &buf, q_real, flags, esc);
+        q_real = string_escape_mem(in, p, out_real, out_size, flags, esc);
 
         test_string_check_buf(name, flags, in, p, out_real, q_real, out_test,
                               q_test);
+
+        test_string_escape_overflow(in, p, flags, esc, q_test, name);
+
 out:
         kfree(in);
         kfree(out_real);
         kfree(out_test);
 }
 
-static __init void test_string_escape_nomem(void)
-{
-        char *in = "\eb \\C\007\"\x90\r]";
-        char out[64], *buf = out;
-        int rc = -ENOMEM, ret;
-
-        ret = string_escape_str_any_np(in, &buf, strlen(in), NULL);
-        if (ret == rc)
-                return;
-
-        pr_err("Test 'escape nomem' failed: got %d instead of %d\n", ret, rc);
-}
-
 static int __init test_string_helpers_init(void)
 {
         unsigned int i;
@@ -342,8 +344,6 @@ static int __init test_string_helpers_init(void)
         for (i = 0; i < (ESCAPE_ANY_NP | ESCAPE_HEX) + 1; i++)
                 test_string_escape("escape 1", escape1, i, TEST_STRING_2_DICT_1);
 
-        test_string_escape_nomem();
-
         return -EINVAL;
 }
 module_init(test_string_helpers_init);
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 4da1e7aaf9d5..3a1e0843f9a2 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -1235,8 +1235,12 @@ char *escaped_string(char *buf, char *end, u8 *addr, struct printf_spec spec,
 
         len = spec.field_width < 0 ? 1 : spec.field_width;
 
-        /* Ignore the error. We print as many characters as we can */
-        string_escape_mem(addr, len, &buf, end - buf, flags, NULL);
+        /*
+         * string_escape_mem() writes as many characters as it can to
+         * the given buffer, and returns the total size of the output
+         * had the buffer been big enough.
+         */
+        buf += string_escape_mem(addr, len, buf, buf < end ? end - buf : 0, flags, NULL);
 
         return buf;
 }