kdb: Use strscpy with destination buffer size

gcc 8.1.0 warns with:

kernel/debug/kdb/kdb_support.c: In function ‘kallsyms_symbol_next’:
kernel/debug/kdb/kdb_support.c:239:4: warning: ‘strncpy’ specified bound depends on the length of the source argument [-Wstringop-overflow=]
     strncpy(prefix_name, name, strlen(name)+1);
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/debug/kdb/kdb_support.c:239:31: note: length computed here

Use strscpy() with the destination buffer size, and use ellipses when
displaying truncated symbols.

v2: Use strscpy()

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Jonathan Toppins <jtoppins@redhat.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Daniel Thompson <daniel.thompson@linaro.org>
Cc: kgdb-bugreport@lists.sourceforge.net
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>

3 files changed, 15 insertions, 12 deletions

diff --git a/kernel/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c
index ed5d34925ad0..6a4b41484afe 100644
--- a/kernel/debug/kdb/kdb_io.c
+++ b/kernel/debug/kdb/kdb_io.c
@@ -216,7 +216,7 @@ static char *kdb_read(char *buffer, size_t bufsize)
         int count;
         int i;
         int diag, dtab_count;
-        int key;
+        int key, buf_size, ret;
 
 
         diag = kdbgetintenv("DTABCOUNT", &dtab_count);
@@ -336,9 +336,8 @@ poll_again:
                 else
                         p_tmp = tmpbuffer;
                 len = strlen(p_tmp);
-                count = kallsyms_symbol_complete(p_tmp,
-                                                 sizeof(tmpbuffer) -
-                                                 (p_tmp - tmpbuffer));
+                buf_size = sizeof(tmpbuffer) - (p_tmp - tmpbuffer);
+                count = kallsyms_symbol_complete(p_tmp, buf_size);
                 if (tab == 2 && count > 0) {
                         kdb_printf("\n%d symbols are found.", count);
                         if (count > dtab_count) {
@@ -350,9 +349,13 @@ poll_again:
                         }
                         kdb_printf("\n");
                         for (i = 0; i < count; i++) {
-                                if (WARN_ON(!kallsyms_symbol_next(p_tmp, i)))
+                                ret = kallsyms_symbol_next(p_tmp, i, buf_size);
+                                if (WARN_ON(!ret))
                                         break;
-                                kdb_printf("%s ", p_tmp);
+                                if (ret != -E2BIG)
+                                        kdb_printf("%s ", p_tmp);
+                                else
+                                        kdb_printf("%s... ", p_tmp);
                                 *(p_tmp + len) = '\0';
                         }
                         if (i >= dtab_count)
diff --git a/kernel/debug/kdb/kdb_private.h b/kernel/debug/kdb/kdb_private.h
index 1e5a502ba4a7..2118d8258b7c 100644
--- a/kernel/debug/kdb/kdb_private.h
+++ b/kernel/debug/kdb/kdb_private.h
@@ -83,7 +83,7 @@ typedef struct __ksymtab {
                 unsigned long sym_start;
                 unsigned long sym_end;
                 } kdb_symtab_t;
-extern int kallsyms_symbol_next(char *prefix_name, int flag);
+extern int kallsyms_symbol_next(char *prefix_name, int flag, int buf_size);
 extern int kallsyms_symbol_complete(char *prefix_name, int max_len);
 
 /* Exported Symbols for kernel loadable modules to use. */
diff --git a/kernel/debug/kdb/kdb_support.c b/kernel/debug/kdb/kdb_support.c
index 987eb73284d2..b14b0925c184 100644
--- a/kernel/debug/kdb/kdb_support.c
+++ b/kernel/debug/kdb/kdb_support.c
@@ -221,11 +221,13 @@ int kallsyms_symbol_complete(char *prefix_name, int max_len)
  * Parameters:
  *      prefix_name     prefix of a symbol name to lookup
  *      flag    0 means search from the head, 1 means continue search.
+ *      buf_size        maximum length that can be written to prefix_name
+ *                      buffer
  * Returns:
  *      1 if a symbol matches the given prefix.
  *      0 if no string found
  */
-int kallsyms_symbol_next(char *prefix_name, int flag)
+int kallsyms_symbol_next(char *prefix_name, int flag, int buf_size)
 {
         int prefix_len = strlen(prefix_name);
         static loff_t pos;
@@ -235,10 +237,8 @@ int kallsyms_symbol_next(char *prefix_name, int flag)
                 pos = 0;
 
         while ((name = kdb_walk_kallsyms(&pos))) {
-                if (strncmp(name, prefix_name, prefix_len) == 0) {
-                        strncpy(prefix_name, name, strlen(name)+1);
-                        return 1;
-                }
+                if (!strncmp(name, prefix_name, prefix_len))
+                        return strscpy(prefix_name, name, buf_size);
         }
         return 0;
 }