misc/e4defrag: fix -Wstringop-truncation warnings

Fix two -Wstringop-truncation warnings in is_ext4() by simplifying how
how mnt_type is handled and by using the correct bound for mnt_fsname.

Fix a -Wstringop-truncation warning in main() by replacing the fragile
pattern 'strncpy(dst, src, strnlen(src, N))', which doesn't
null-terminate the destination string, with a standard string copy.  (It
happened to work anyway because dst happens to be zero-initialized.)

These warnings showed up when building with -Wall with gcc 8 or later.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/e4defrag.c b/misc/e4defrag.c
index 9ec265f2e1b29a5c5bb704190f5e18b4cf4957e7..33bd05d2c9bdbeec338cebf53bb32175206bb3c8 100644 (file)
--- a/misc/e4defrag.c
+++ b/misc/e4defrag.c
@@ -258,12 +258,12 @@ static int get_mount_point(const char *devname, char *mount_point,
  *
  * @file:              the file's name.
  */
-static int is_ext4(const char *file, char *devname)
+static int is_ext4(const char *file, char devname[PATH_MAX + 1])
 {
        int     maxlen = 0;
        int     len, ret;
+       int     type_is_ext4 = 0;
        FILE    *fp = NULL;
-       char    *mnt_type = NULL;
        /* Refer to /etc/mtab */
        const char      *mtab = MOUNTED;
        char    file_path[PATH_MAX + 1];
@@ -307,26 +307,16 @@ static int is_ext4(const char *file, char *devname)
 
                maxlen = len;
 
-               mnt_type = realloc(mnt_type, strlen(mnt->mnt_type) + 1);
-               if (mnt_type == NULL) {
-                       endmntent(fp);
-                       return -1;
-               }
-               memset(mnt_type, 0, strlen(mnt->mnt_type) + 1);
-               strncpy(mnt_type, mnt->mnt_type, strlen(mnt->mnt_type));
+               type_is_ext4 = !strcmp(mnt->mnt_type, FS_EXT4);
                strncpy(lost_found_dir, mnt->mnt_dir, PATH_MAX);
-               strncpy(devname, mnt->mnt_fsname, strlen(mnt->mnt_fsname) + 1);
+               strncpy(devname, mnt->mnt_fsname, PATH_MAX);
        }
 
        endmntent(fp);
-       if (mnt_type && strcmp(mnt_type, FS_EXT4) == 0) {
-               FREE(mnt_type);
+       if (type_is_ext4)
                return 0;
-       } else {
-               FREE(mnt_type);
-               PRINT_ERR_MSG(NGMSG_EXT4);
-               return -1;
-       }
+       PRINT_ERR_MSG(NGMSG_EXT4);
+       return -1;
 }
 
 /*
@@ -1865,11 +1855,9 @@ int main(int argc, char *argv[])
                        /* fall through */
                case DEVNAME:
                        if (arg_type == DEVNAME) {
-                               strncpy(lost_found_dir, dir_name,
-                                       strnlen(dir_name, PATH_MAX));
+                               strcpy(lost_found_dir, dir_name);
                                strncat(lost_found_dir, "/lost+found/",
-                                       PATH_MAX - strnlen(lost_found_dir,
-                                                          PATH_MAX));
+                                       PATH_MAX - strlen(lost_found_dir));
                        }
 
                        nftw64(dir_name, calc_entry_counts, FTW_OPEN_FD, flags);