s390/zcrypt: Use scnprintf() for avoiding potential buffer overflow

Since snprintf() returns the would-be-output size instead of the
actual output size, the succeeding calls may go beyond the given
buffer limit.  Fix it by replacing with scnprintf().

Message-Id: <20200311090915.21059-1-tiwai@suse.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/drivers/s390/crypto/zcrypt_cex4.c b/drivers/s390/crypto/zcrypt_cex4.c
index 9a9d02e..6fc1ea7 100644 (file)
--- a/drivers/s390/crypto/zcrypt_cex4.c
+++ b/drivers/s390/crypto/zcrypt_cex4.c
@@ -128,16 +128,18 @@ static ssize_t cca_mkvps_show(struct device *dev,
                n = snprintf(buf, PAGE_SIZE, "AES NEW: - -\n");
 
        if (ci.cur_mk_state >= '1' && ci.cur_mk_state <= '2')
-               n += snprintf(buf + n, PAGE_SIZE - n, "AES CUR: %s 0x%016llx\n",
-                             cao_state[ci.cur_mk_state - '1'], ci.cur_mkvp);
+               n += scnprintf(buf + n, PAGE_SIZE - n,
+                              "AES CUR: %s 0x%016llx\n",
+                              cao_state[ci.cur_mk_state - '1'], ci.cur_mkvp);
        else
-               n += snprintf(buf + n, PAGE_SIZE - n, "AES CUR: - -\n");
+               n += scnprintf(buf + n, PAGE_SIZE - n, "AES CUR: - -\n");
 
        if (ci.old_mk_state >= '1' && ci.old_mk_state <= '2')
-               n += snprintf(buf + n, PAGE_SIZE - n, "AES OLD: %s 0x%016llx\n",
-                             cao_state[ci.old_mk_state - '1'], ci.old_mkvp);
+               n += scnprintf(buf + n, PAGE_SIZE - n,
+                              "AES OLD: %s 0x%016llx\n",
+                              cao_state[ci.old_mk_state - '1'], ci.old_mkvp);
        else
-               n += snprintf(buf + n, PAGE_SIZE - n, "AES OLD: - -\n");
+               n += scnprintf(buf + n, PAGE_SIZE - n, "AES OLD: - -\n");
 
        return n;
 }
@@ -251,11 +253,11 @@ static ssize_t ep11_card_op_modes_show(struct device *dev,
                if (ci.op_mode & (1 << ep11_op_modes[i].mode_bit)) {
                        if (n > 0)
                                buf[n++] = ' ';
-                       n += snprintf(buf + n, PAGE_SIZE - n,
-                                     "%s", ep11_op_modes[i].mode_txt);
+                       n += scnprintf(buf + n, PAGE_SIZE - n,
+                                      "%s", ep11_op_modes[i].mode_txt);
                }
        }
-       n += snprintf(buf + n, PAGE_SIZE - n, "\n");
+       n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
 
        return n;
 }
@@ -305,21 +307,21 @@ static ssize_t ep11_mkvps_show(struct device *dev,
                             cwk_state[di.cur_wk_state - '0']);
                bin2hex(buf + n, di.cur_wkvp, sizeof(di.cur_wkvp));
                n += 2 * sizeof(di.cur_wkvp);
-               n += snprintf(buf + n, PAGE_SIZE - n, "\n");
+               n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
        } else
                n = snprintf(buf, PAGE_SIZE, "WK CUR: - -\n");
 
        if (di.new_wk_state == '0') {
-               n += snprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s -\n",
-                             nwk_state[di.new_wk_state - '0']);
+               n += scnprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s -\n",
+                              nwk_state[di.new_wk_state - '0']);
        } else if (di.new_wk_state >= '1' && di.new_wk_state <= '2') {
-               n += snprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s 0x",
-                             nwk_state[di.new_wk_state - '0']);
+               n += scnprintf(buf + n, PAGE_SIZE - n, "WK NEW: %s 0x",
+                              nwk_state[di.new_wk_state - '0']);
                bin2hex(buf + n, di.new_wkvp, sizeof(di.new_wkvp));
                n += 2 * sizeof(di.new_wkvp);
-               n += snprintf(buf + n, PAGE_SIZE - n, "\n");
+               n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
        } else
-               n += snprintf(buf + n, PAGE_SIZE - n, "WK NEW: - -\n");
+               n += scnprintf(buf + n, PAGE_SIZE - n, "WK NEW: - -\n");
 
        return n;
 }
@@ -346,11 +348,11 @@ static ssize_t ep11_queue_op_modes_show(struct device *dev,
                if (di.op_mode & (1 << ep11_op_modes[i].mode_bit)) {
                        if (n > 0)
                                buf[n++] = ' ';
-                       n += snprintf(buf + n, PAGE_SIZE - n,
-                                     "%s", ep11_op_modes[i].mode_txt);
+                       n += scnprintf(buf + n, PAGE_SIZE - n,
+                                      "%s", ep11_op_modes[i].mode_txt);
                }
        }
-       n += snprintf(buf + n, PAGE_SIZE - n, "\n");
+       n += scnprintf(buf + n, PAGE_SIZE - n, "\n");
 
        return n;
 }