From 53c78143c411170cef79f75938ac0051c59cafa7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A1draig=20Brady?= <address@hidden>
Date: Sun, 10 Jun 2018 23:02:58 -0700
Subject: [PATCH] rm: add --preserve-root=all to protect mount points

* src/remove.c (rm_fts): With the --preserve-root=all extension,
skip command line arguments that are mount points.
---
 src/mv.c     |  2 ++
 src/remove.c | 35 +++++++++++++++++++++++++++++++++++
 src/remove.h |  4 ++++
 src/rm.c     | 14 +++++++++++++-
 4 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/src/mv.c b/src/mv.c
index edc1e73..b6dd72d 100644
--- a/src/mv.c
+++ b/src/mv.c
@@ -99,6 +99,8 @@ rm_option_init (struct rm_options *x)
       die (EXIT_FAILURE, errno, _("failed to get attributes of %s"),
            quoteaf ("/"));
   }
+
+  x->preserve_all_root = false;
 }
 
 static void
diff --git a/src/remove.c b/src/remove.c
index eafb964..6ff837c 100644
--- a/src/remove.c
+++ b/src/remove.c
@@ -24,6 +24,7 @@
 #include "system.h"
 #include "error.h"
 #include "file-type.h"
+#include "filenamecat.h"
 #include "ignore-value.h"
 #include "remove.h"
 #include "root-dev-ino.h"
@@ -459,6 +460,40 @@ rm_fts (FTS *fts, FTSENT *ent, struct rm_options const *x)
               fts_skip_tree (fts, ent);
               return RM_ERROR;
             }
+
+          /* If a command line argument is a mount point and
+             --preserve-root=all is in effect, diagnose and skip it.
+             This doesn't handle "/", but that's handled above.  */
+          if (x->preserve_all_root)
+            {
+              bool failed = false;
+              char *parent = file_name_concat (ent->fts_accpath, "..", NULL);
+              struct stat statbuf;
+
+              if (!parent || lstat (parent, &statbuf))
+                {
+                  error (0, 0,
+                         _("failed to stat %s: skipping %s"),
+                         quoteaf_n (0, parent),
+                         quoteaf_n (1, ent->fts_accpath));
+                  failed = true;
+                }
+
+              free (parent);
+
+              if (failed || fts->fts_dev != statbuf.st_dev)
+                {
+                  if (! failed)
+                    {
+                      error (0, 0,
+                             _("skipping %s, since it's a mount point"),
+                             quoteaf (ent->fts_path));
+                      error (0, 0, _("and --preserve-root=all is in effect"));
+                    }
+                  fts_skip_tree (fts, ent);
+                  return RM_ERROR;
+                }
+            }
         }
 
       {
diff --git a/src/remove.h b/src/remove.h
index 2ce3a16..8fc6171 100644
--- a/src/remove.h
+++ b/src/remove.h
@@ -56,6 +56,10 @@ struct rm_options
      and preserving '/'.  Otherwise NULL.  */
   struct dev_ino *root_dev_ino;
 
+  /* If true, do not traverse into (or remove) any directory that is
+     the root of a file system.  I.E. a mount point.  */
+  bool preserve_all_root;
+
   /* If nonzero, stdin is a tty.  */
   bool stdin_tty;
 
diff --git a/src/rm.c b/src/rm.c
index dbc0cb7..82cf132 100644
--- a/src/rm.c
+++ b/src/rm.c
@@ -67,7 +67,7 @@ static struct option const long_opts[] =
 
   {"one-file-system", no_argument, NULL, ONE_FILE_SYSTEM},
   {"no-preserve-root", no_argument, NULL, NO_PRESERVE_ROOT},
-  {"preserve-root", no_argument, NULL, PRESERVE_ROOT},
+  {"preserve-root", optional_argument, NULL, PRESERVE_ROOT},
 
   /* This is solely for testing.  Do not document.  */
   /* It is relatively difficult to ensure that there is a tty on stdin.
@@ -192,6 +192,7 @@ rm_option_init (struct rm_options *x)
   x->remove_empty_directories = false;
   x->recursive = false;
   x->root_dev_ino = NULL;
+  x->preserve_all_root = false;
   x->stdin_tty = isatty (STDIN_FILENO);
   x->verbose = false;
 
@@ -294,6 +295,17 @@ main (int argc, char **argv)
           break;
 
         case PRESERVE_ROOT:
+          if (optarg)
+            {
+              if STREQ (optarg, "all")
+                x.preserve_all_root = true;
+              else
+                {
+                  die (EXIT_FAILURE, 0,
+                       _("unrecognized --preserve-root argument: %s"),
+                       quoteaf (optarg));
+                }
+            }
           preserve_root = true;
           break;
 
-- 
2.9.3