3 files changed, 541 insertions, 4 deletions

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index 5a30f2a86239..6eb567ac56bc 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -37,4 +37,35 @@ static inline int string_unescape_any_inplace(char *buf)
         return string_unescape_any(buf, buf, 0);
 }
 
+#define ESCAPE_SPACE            0x01
+#define ESCAPE_SPECIAL          0x02
+#define ESCAPE_NULL             0x04
+#define ESCAPE_OCTAL            0x08
+#define ESCAPE_ANY              \
+        (ESCAPE_SPACE | ESCAPE_OCTAL | ESCAPE_SPECIAL | ESCAPE_NULL)
+#define ESCAPE_NP               0x10
+#define ESCAPE_ANY_NP           (ESCAPE_ANY | ESCAPE_NP)
+#define ESCAPE_HEX              0x20
+
+int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
+                unsigned int flags, const char *esc);
+
+static inline int string_escape_mem_any_np(const char *src, size_t isz,
+                char **dst, size_t osz, const char *esc)
+{
+        return string_escape_mem(src, isz, dst, osz, ESCAPE_ANY_NP, esc);
+}
+
+static inline int string_escape_str(const char *src, char **dst, size_t sz,
+                unsigned int flags, const char *esc)
+{
+        return string_escape_mem(src, strlen(src), dst, sz, flags, esc);
+}
+
+static inline int string_escape_str_any_np(const char *src, char **dst,
+                size_t sz, const char *esc)
+{
+        return string_escape_str(src, dst, sz, ESCAPE_ANY_NP, esc);
+}
+
 #endif
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 74ec60469640..58b78ba57439 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -8,6 +8,8 @@
 #include <linux/math64.h>
 #include <linux/export.h>
 #include <linux/ctype.h>
+#include <linux/errno.h>
+#include <linux/string.h>
 #include <linux/string_helpers.h>
 
 /**
@@ -240,3 +242,275 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
         return out - dst;
 }
 EXPORT_SYMBOL(string_unescape);
+
+static int escape_passthrough(unsigned char c, char **dst, size_t *osz)
+{
+        char *out = *dst;
+
+        if (*osz < 1)
+                return -ENOMEM;
+
+        *out++ = c;
+
+        *dst = out;
+        *osz -= 1;
+
+        return 1;
+}
+
+static int escape_space(unsigned char c, char **dst, size_t *osz)
+{
+        char *out = *dst;
+        unsigned char to;
+
+        if (*osz < 2)
+                return -ENOMEM;
+
+        switch (c) {
+        case '\n':
+                to = 'n';
+                break;
+        case '\r':
+                to = 'r';
+                break;
+        case '\t':
+                to = 't';
+                break;
+        case '\v':
+                to = 'v';
+                break;
+        case '\f':
+                to = 'f';
+                break;
+        default:
+                return 0;
+        }
+
+        *out++ = '\\';
+        *out++ = to;
+
+        *dst = out;
+        *osz -= 2;
+
+        return 1;
+}
+
+static int escape_special(unsigned char c, char **dst, size_t *osz)
+{
+        char *out = *dst;
+        unsigned char to;
+
+        if (*osz < 2)
+                return -ENOMEM;
+
+        switch (c) {
+        case '\\':
+                to = '\\';
+                break;
+        case '\a':
+                to = 'a';
+                break;
+        case '\e':
+                to = 'e';
+                break;
+        default:
+                return 0;
+        }
+
+        *out++ = '\\';
+        *out++ = to;
+
+        *dst = out;
+        *osz -= 2;
+
+        return 1;
+}
+
+static int escape_null(unsigned char c, char **dst, size_t *osz)
+{
+        char *out = *dst;
+
+        if (*osz < 2)
+                return -ENOMEM;
+
+        if (c)
+                return 0;
+
+        *out++ = '\\';
+        *out++ = '0';
+
+        *dst = out;
+        *osz -= 2;
+
+        return 1;
+}
+
+static int escape_octal(unsigned char c, char **dst, size_t *osz)
+{
+        char *out = *dst;
+
+        if (*osz < 4)
+                return -ENOMEM;
+
+        *out++ = '\\';
+        *out++ = ((c >> 6) & 0x07) + '0';
+        *out++ = ((c >> 3) & 0x07) + '0';
+        *out++ = ((c >> 0) & 0x07) + '0';
+
+        *dst = out;
+        *osz -= 4;
+
+        return 1;
+}
+
+static int escape_hex(unsigned char c, char **dst, size_t *osz)
+{
+        char *out = *dst;
+
+        if (*osz < 4)
+                return -ENOMEM;
+
+        *out++ = '\\';
+        *out++ = 'x';
+        *out++ = hex_asc_hi(c);
+        *out++ = hex_asc_lo(c);
+
+        *dst = out;
+        *osz -= 4;
+
+        return 1;
+}
+
+/**
+ * string_escape_mem - quote characters in the given memory buffer
+ * @src:        source buffer (unescaped)
+ * @isz:        source buffer size
+ * @dst:        destination buffer (escaped)
+ * @osz:        destination buffer size
+ * @flags:      combination of the flags (bitwise OR):
+ *      %ESCAPE_SPACE:
+ *              '\f' - form feed
+ *              '\n' - new line
+ *              '\r' - carriage return
+ *              '\t' - horizontal tab
+ *              '\v' - vertical tab
+ *      %ESCAPE_SPECIAL:
+ *              '\\' - backslash
+ *              '\a' - alert (BEL)
+ *              '\e' - escape
+ *      %ESCAPE_NULL:
+ *              '\0' - null
+ *      %ESCAPE_OCTAL:
+ *              '\NNN' - byte with octal value NNN (3 digits)
+ *      %ESCAPE_ANY:
+ *              all previous together
+ *      %ESCAPE_NP:
+ *              escape only non-printable characters (checked by isprint)
+ *      %ESCAPE_ANY_NP:
+ *              all previous together
+ *      %ESCAPE_HEX:
+ *              '\xHH' - byte with hexadecimal value HH (2 digits)
+ * @esc:        NULL-terminated string of characters any of which, if found in
+ *              the source, has to be escaped
+ *
+ * Description:
+ * The process of escaping byte buffer includes several parts. They are applied
+ * in the following sequence.
+ *      1. The character is matched to the printable class, if asked, and in
+ *         case of match it passes through to the output.
+ *      2. The character is not matched to the one from @esc string and thus
+ *         must go as is to the output.
+ *      3. The character is checked if it falls into the class given by @flags.
+ *         %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any
+ *         character. Note that they actually can't go together, otherwise
+ *         %ESCAPE_HEX will be ignored.
+ *
+ * Caller must provide valid source and destination pointers. Be aware that
+ * destination buffer will not be NULL-terminated, thus caller have to append
+ * 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.
+ */
+int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
+                      unsigned int flags, const char *esc)
+{
+        char *out = *dst, *p = out;
+        bool is_dict = esc && *esc;
+        int ret = 0;
+
+        while (isz--) {
+                unsigned char c = *src++;
+
+                /*
+                 * Apply rules in the following sequence:
+                 *      - the character is printable, when @flags has
+                 *        %ESCAPE_NP bit set
+                 *      - the @esc string is supplied and does not contain a
+                 *        character under question
+                 *      - the character doesn't fall into a class of symbols
+                 *        defined by given @flags
+                 * In these cases we just pass through a character to the
+                 * output buffer.
+                 */
+                if ((flags & ESCAPE_NP && isprint(c)) ||
+                    (is_dict && !strchr(esc, c))) {
+                        /* do nothing */
+                } else {
+                        if (flags & ESCAPE_SPACE) {
+                                ret = escape_space(c, &p, &osz);
+                                if (ret < 0)
+                                        break;
+                                if (ret > 0)
+                                        continue;
+                        }
+
+                        if (flags & ESCAPE_SPECIAL) {
+                                ret = escape_special(c, &p, &osz);
+                                if (ret < 0)
+                                        break;
+                                if (ret > 0)
+                                        continue;
+                        }
+
+                        if (flags & ESCAPE_NULL) {
+                                ret = escape_null(c, &p, &osz);
+                                if (ret < 0)
+                                        break;
+                                if (ret > 0)
+                                        continue;
+                        }
+
+                        /* ESCAPE_OCTAL and ESCAPE_HEX always go last */
+                        if (flags & ESCAPE_OCTAL) {
+                                ret = escape_octal(c, &p, &osz);
+                                if (ret < 0)
+                                        break;
+                                continue;
+                        }
+                        if (flags & ESCAPE_HEX) {
+                                ret = escape_hex(c, &p, &osz);
+                                if (ret < 0)
+                                        break;
+                                continue;
+                        }
+                }
+
+                ret = escape_passthrough(c, &p, &osz);
+                if (ret < 0)
+                        break;
+        }
+
+        *dst = p;
+
+        if (ret < 0)
+                return ret;
+
+        return p - out;
+}
+EXPORT_SYMBOL(string_escape_mem);
diff --git a/lib/test-string_helpers.c b/lib/test-string_helpers.c
index ac44c9245dcf..ab0d30e1e18f 100644
--- a/lib/test-string_helpers.c
+++ b/lib/test-string_helpers.c
@@ -5,6 +5,7 @@
 
 #include <linux/init.h>
 #include <linux/kernel.h>
+#include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/string.h>
@@ -62,10 +63,14 @@ static const struct test_string strings[] __initconst = {
 static void __init test_string_unescape(const char *name, unsigned int flags,
                                         bool inplace)
 {
-        char in[256];
-        char out_test[256];
-        char out_real[256];
-        int i, p = 0, q_test = 0, q_real = sizeof(out_real);
+        int q_real = 256;
+        char *in = kmalloc(q_real, GFP_KERNEL);
+        char *out_test = kmalloc(q_real, GFP_KERNEL);
+        char *out_real = kmalloc(q_real, GFP_KERNEL);
+        int i, p = 0, q_test = 0;
+
+        if (!in || !out_test || !out_real)
+                goto out;
 
         for (i = 0; i < ARRAY_SIZE(strings); i++) {
                 const char *s = strings[i].in;
@@ -100,6 +105,223 @@ static void __init test_string_unescape(const char *name, unsigned int flags,
 
         test_string_check_buf(name, flags, in, p - 1, out_real, q_real,
                               out_test, q_test);
+out:
+        kfree(out_real);
+        kfree(out_test);
+        kfree(in);
+}
+
+struct test_string_1 {
+        const char *out;
+        unsigned int flags;
+};
+
+#define TEST_STRING_2_MAX_S1            32
+struct test_string_2 {
+        const char *in;
+        struct test_string_1 s1[TEST_STRING_2_MAX_S1];
+};
+
+#define TEST_STRING_2_DICT_0            NULL
+static const struct test_string_2 escape0[] __initconst = {{
+        .in = "\f\\ \n\r\t\v",
+        .s1 = {{
+                .out = "\\f\\ \\n\\r\\t\\v",
+                .flags = ESCAPE_SPACE,
+        },{
+                .out = "\\f\\134\\040\\n\\r\\t\\v",
+                .flags = ESCAPE_SPACE | ESCAPE_OCTAL,
+        },{
+                .out = "\\f\\x5c\\x20\\n\\r\\t\\v",
+                .flags = ESCAPE_SPACE | ESCAPE_HEX,
+        },{
+                /* terminator */
+        }},
+},{
+        .in = "\\h\\\"\a\e\\",
+        .s1 = {{
+                .out = "\\\\h\\\\\"\\a\\e\\\\",
+                .flags = ESCAPE_SPECIAL,
+        },{
+                .out = "\\\\\\150\\\\\\042\\a\\e\\\\",
+                .flags = ESCAPE_SPECIAL | ESCAPE_OCTAL,
+        },{
+                .out = "\\\\\\x68\\\\\\x22\\a\\e\\\\",
+                .flags = ESCAPE_SPECIAL | ESCAPE_HEX,
+        },{
+                /* terminator */
+        }},
+},{
+        .in = "\eb \\C\007\"\x90\r]",
+        .s1 = {{
+                .out = "\eb \\C\007\"\x90\\r]",
+                .flags = ESCAPE_SPACE,
+        },{
+                .out = "\\eb \\\\C\\a\"\x90\r]",
+                .flags = ESCAPE_SPECIAL,
+        },{
+                .out = "\\eb \\\\C\\a\"\x90\\r]",
+                .flags = ESCAPE_SPACE | ESCAPE_SPECIAL,
+        },{
+                .out = "\\033\\142\\040\\134\\103\\007\\042\\220\\015\\135",
+                .flags = ESCAPE_OCTAL,
+        },{
+                .out = "\\033\\142\\040\\134\\103\\007\\042\\220\\r\\135",
+                .flags = ESCAPE_SPACE | ESCAPE_OCTAL,
+        },{
+                .out = "\\e\\142\\040\\\\\\103\\a\\042\\220\\015\\135",
+                .flags = ESCAPE_SPECIAL | ESCAPE_OCTAL,
+        },{
+                .out = "\\e\\142\\040\\\\\\103\\a\\042\\220\\r\\135",
+                .flags = ESCAPE_SPACE | ESCAPE_SPECIAL | ESCAPE_OCTAL,
+        },{
+                .out = "\eb \\C\007\"\x90\r]",
+                .flags = ESCAPE_NP,
+        },{
+                .out = "\eb \\C\007\"\x90\\r]",
+                .flags = ESCAPE_SPACE | ESCAPE_NP,
+        },{
+                .out = "\\eb \\C\\a\"\x90\r]",
+                .flags = ESCAPE_SPECIAL | ESCAPE_NP,
+        },{
+                .out = "\\eb \\C\\a\"\x90\\r]",
+                .flags = ESCAPE_SPACE | ESCAPE_SPECIAL | ESCAPE_NP,
+        },{
+                .out = "\\033b \\C\\007\"\\220\\015]",
+                .flags = ESCAPE_OCTAL | ESCAPE_NP,
+        },{
+                .out = "\\033b \\C\\007\"\\220\\r]",
+                .flags = ESCAPE_SPACE | ESCAPE_OCTAL | ESCAPE_NP,
+        },{
+                .out = "\\eb \\C\\a\"\\220\\r]",
+                .flags = ESCAPE_SPECIAL | ESCAPE_SPACE | ESCAPE_OCTAL |
+                         ESCAPE_NP,
+        },{
+                .out = "\\x1bb \\C\\x07\"\\x90\\x0d]",
+                .flags = ESCAPE_NP | ESCAPE_HEX,
+        },{
+                /* terminator */
+        }},
+},{
+        /* terminator */
+}};
+
+#define TEST_STRING_2_DICT_1            "b\\ \t\r"
+static const struct test_string_2 escape1[] __initconst = {{
+        .in = "\f\\ \n\r\t\v",
+        .s1 = {{
+                .out = "\f\\134\\040\n\\015\\011\v",
+                .flags = ESCAPE_OCTAL,
+        },{
+                .out = "\f\\x5c\\x20\n\\x0d\\x09\v",
+                .flags = ESCAPE_HEX,
+        },{
+                /* terminator */
+        }},
+},{
+        .in = "\\h\\\"\a\e\\",
+        .s1 = {{
+                .out = "\\134h\\134\"\a\e\\134",
+                .flags = ESCAPE_OCTAL,
+        },{
+                /* terminator */
+        }},
+},{
+        .in = "\eb \\C\007\"\x90\r]",
+        .s1 = {{
+                .out = "\e\\142\\040\\134C\007\"\x90\\015]",
+                .flags = ESCAPE_OCTAL,
+        },{
+                /* terminator */
+        }},
+},{
+        /* terminator */
+}};
+
+static __init const char *test_string_find_match(const struct test_string_2 *s2,
+                                                 unsigned int flags)
+{
+        const struct test_string_1 *s1 = s2->s1;
+        unsigned int i;
+
+        if (!flags)
+                return s2->in;
+
+        /* Test cases are NULL-aware */
+        flags &= ~ESCAPE_NULL;
+
+        /* ESCAPE_OCTAL has a higher priority */
+        if (flags & ESCAPE_OCTAL)
+                flags &= ~ESCAPE_HEX;
+
+        for (i = 0; i < TEST_STRING_2_MAX_S1 && s1->out; i++, s1++)
+                if (s1->flags == flags)
+                        return s1->out;
+        return NULL;
+}
+
+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);
+        char *in = kmalloc(256, GFP_KERNEL);
+        char *buf = out_real;
+        int p = 0, q_test = 0;
+
+        if (!out_test || !out_real || !in)
+                goto out;
+
+        for (; s2->in; s2++) {
+                const char *out;
+                int len;
+
+                /* NULL injection */
+                if (flags & ESCAPE_NULL) {
+                        in[p++] = '\0';
+                        out_test[q_test++] = '\\';
+                        out_test[q_test++] = '0';
+                }
+
+                /* Don't try strings that have no output */
+                out = test_string_find_match(s2, flags);
+                if (!out)
+                        continue;
+
+                /* Copy string to in buffer */
+                len = strlen(s2->in);
+                memcpy(&in[p], s2->in, len);
+                p += len;
+
+                /* Copy expected result for given flags */
+                len = strlen(out);
+                memcpy(&out_test[q_test], out, len);
+                q_test += len;
+        }
+
+        q_real = string_escape_mem(in, p, &buf, q_real, flags, esc);
+
+        test_string_check_buf(name, flags, in, p, out_real, q_real, out_test,
+                              q_test);
+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)
@@ -112,6 +334,16 @@ static int __init test_string_helpers_init(void)
         test_string_unescape("unescape inplace",
                              get_random_int() % (UNESCAPE_ANY + 1), true);
 
+        /* Without dictionary */
+        for (i = 0; i < (ESCAPE_ANY_NP | ESCAPE_HEX) + 1; i++)
+                test_string_escape("escape 0", escape0, i, TEST_STRING_2_DICT_0);
+
+        /* With dictionary */
+        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);