Fix "fuser" command to properly deal with an invalid argument

The man page of the "fuser" command suggests that the argument can be a
full pathname or inode address. However, the "fuser" command accepts an
invalid argument and prints a bogus result as below:

  crash> fuser x
   PID         TASK        COMM             USAGE
  100507  ffff9914431f4c80  "packagekitd"    fd
  100508  ffff991574e59980  "gmain"          fd
  100509  ffff9914431f3300  "gdbus"          fd
  102020  ffff991574400000  "sshd"           fd
  102043  ffff991441d19980  "sshd"           fd

The current fuser command has no checking mechanism to determine if an
argument is valid or not. Let's add it to handle such cases.

With the patch:
  crash> fuser x
  fuser: invalid argument: x

In addition, also add a note that fuser does not expect an argument other
than an inode address and full pathname, and if others are specified, the
output can be an unexpected result.

Reported-by: Buland Kumar Singh <bsingh@redhat.com>
Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
Signed-off-by: Kazuhito Hagio <k-hagio-ab@nec.com>

filesys.c

@@ -3398,6 +3398,7 @@ cmd_fuser(void)
 	char fuser_header[BUFSIZE];
 	int doing_fds, doing_mmap, len;
 	int fuser_header_printed, lockd_header_printed;
+	ulong spec_addr;
 
         while ((c = getopt(argcnt, args, "")) != EOF) {
                 switch(c)
@@ -3421,7 +3422,12 @@ cmd_fuser(void)
 
 	doing_fds = doing_mmap = 0;
 	while (args[optind]) {
-                spec_string = args[optind];
+		spec_string = args[optind];
+		spec_addr = htol(spec_string, RETURN_ON_ERROR|QUIET, NULL);
+		if ((spec_addr == BADADDR || !IS_KVADDR(spec_addr)) &&
+		    spec_string[0] != '/')
+			error(FATAL, "invalid argument: %s\n", args[optind]);
+
 		if (STRNEQ(spec_string, "0x") && hexadecimal(spec_string, 0))
 			shift_string_left(spec_string, 2);
 		len = strlen(spec_string);

help.c

@@ -7990,6 +7990,10 @@ char *help_fuser[] = {
 "  listed.\n",
 "    pathname  the full pathname of the file.",
 "    inode     the hexadecimal inode address for the file.",
+"",
+"  NOTE: This commmand does not expect arguments other than inode address",
+"  or full pathname.  If others are specified, the command may accept them,",
+"  but an unexpected output can be displayed.",
 "\nEXAMPLES",
 "  Display the tasks using file /usr/lib/libkfm.so.2.0.0\n",
 "    %s> fuser /usr/lib/libkfm.so.2.0.0",