patch 8.0.0493: crash with cd command with very long argument

Problem:    Crash with cd command with very long argument.
Solution:   Check for running out of space. (Dominique pending, closes #1576)

src/Makefile

@@ -2096,6 +2096,7 @@ test_arglist \
 	test_backspace_opt \
 	test_breakindent \
 	test_bufwintabinfo \
+	test_cd \
 	test_cdo \
 	test_changedtick \
 	test_channel \

src/misc2.c

@@ -4636,14 +4636,24 @@ vim_findfile(void *search_ctx_arg)
 		/* if we have a start dir copy it in */
 		if (!vim_isAbsName(stackp->ffs_fix_path)
 						&& search_ctx->ffsc_start_dir)
+		{
+		    if (STRLEN(search_ctx->ffsc_start_dir) + 1 < MAXPATHL)
 		    {
 			STRCPY(file_path, search_ctx->ffsc_start_dir);
 			add_pathsep(file_path);
 		    }
+		    else
+			goto fail;
+		}
 
 		/* append the fix part of the search path */
+		if (STRLEN(file_path) + STRLEN(stackp->ffs_fix_path) + 1 < MAXPATHL)
+		{
 		    STRCAT(file_path, stackp->ffs_fix_path);
 		    add_pathsep(file_path);
+		}
+		else
+		    goto fail;
 
 #ifdef FEAT_PATH_EXTRA
 		rest_of_wildcards = stackp->ffs_wc_path;
@@ -4660,7 +4670,10 @@ vim_findfile(void *search_ctx_arg)
 			if (*p > 0)
 			{
 			    (*p)--;
+			    if (len + 1 < MAXPATHL)
 				file_path[len++] = '*';
+			    else
+				goto fail;
 			}
 
 			if (*p == 0)
@@ -4688,7 +4701,10 @@ vim_findfile(void *search_ctx_arg)
 		     */
 		    while (*rest_of_wildcards
 			    && !vim_ispathsep(*rest_of_wildcards))
+			if (len + 1 < MAXPATHL)
 			    file_path[len++] = *rest_of_wildcards++;
+			else
+			    goto fail;
 
 		    file_path[len] = NUL;
 		    if (vim_ispathsep(*rest_of_wildcards))
@@ -4749,9 +4765,15 @@ vim_findfile(void *search_ctx_arg)
 
 			/* prepare the filename to be checked for existence
 			 * below */
+			if (STRLEN(stackp->ffs_filearray[i]) + 1
+				+ STRLEN(search_ctx->ffsc_file_to_search) < MAXPATHL)
+			{
 			    STRCPY(file_path, stackp->ffs_filearray[i]);
 			    add_pathsep(file_path);
 			    STRCAT(file_path, search_ctx->ffsc_file_to_search);
+			}
+			else
+			    goto fail;
 
 			/*
 			 * Try without extra suffix and then with suffixes
@@ -4924,9 +4946,15 @@ vim_findfile(void *search_ctx_arg)
 	    if (*search_ctx->ffsc_start_dir == 0)
 		break;
 
+	    if (STRLEN(search_ctx->ffsc_start_dir) + 1
+		    + STRLEN(search_ctx->ffsc_fix_path) < MAXPATHL)
+	    {
 		STRCPY(file_path, search_ctx->ffsc_start_dir);
 		add_pathsep(file_path);
 		STRCAT(file_path, search_ctx->ffsc_fix_path);
+	    }
+	    else
+		goto fail;
 
 	    /* create a new stack entry */
 	    sptr = ff_create_stack_element(file_path,
@@ -4940,6 +4968,7 @@ vim_findfile(void *search_ctx_arg)
     }
 #endif
 
+fail:
     vim_free(file_path);
     return NULL;
 }

src/testdir/test_alot.vim

@@ -3,6 +3,7 @@
 
 set belloff=all
 source test_assign.vim
+source test_cd.vim
 source test_changedtick.vim
 source test_cursor_func.vim
 source test_delete.vim

src/testdir/test_cd.vim

@@ -0,0 +1,13 @@
+" Test for :cd
+
+func Test_cd_large_path()
+  " This used to crash with a heap write overflow.
+  call assert_fails('cd ' . repeat('x', 5000), 'E472:')
+endfunc
+
+func Test_cd_up_and_down()
+  let path = getcwd()
+  cd ..
+  exe 'cd ' . path
+  call assert_equal(path, getcwd())
+endfunc

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    493,
 /**/
     492,
 /**/