tar: fix interaction of delayed symlink and hardlink creation

function                                             old     new   delta
create_or_remember_link                                -     106    +106
create_links_from_list                                 -      93     +93
find_applet_by_name                                  124     128      +4
unzip_main                                          2724    2726      +2
data_extract_all                                     891     873     -18
create_symlinks_from_list                             64       -     -64
create_or_remember_symlink                            94       -     -94
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 2/1 up/down: 205/-176)           Total: 29 bytes

Signed-off-by: Harald van Dijk <harald@gigawatt.nl>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

archival/cpio.c

@@ -508,7 +508,7 @@ int cpio_main(int argc UNUSED_PARAM, char **argv)
 	while (get_header_cpio(archive_handle) == EXIT_SUCCESS)
 		continue;
 
-	create_symlinks_from_list(archive_handle->symlink_placeholders);
+	create_links_from_list(archive_handle->link_placeholders);
 
 	if (archive_handle->cpio__blocks != (off_t)-1
 	 && !(opt & OPT_QUIET)

archival/libarchive/data_extract_all.c

@@ -122,13 +122,10 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
 
 	/* Handle hard links separately */
 	if (hard_link) {
-		res = link(hard_link, dst_name);
+		create_or_remember_link(&archive_handle->link_placeholders,
-		if (res != 0) {
+				hard_link,
-			/* shared message */
+				dst_name,
-			bb_perror_msg("can't create %slink '%s' to '%s'",
+				1);
-				"hard",	dst_name, hard_link
-			);
-		}
 		/* Hardlinks have no separate mode/ownership, skip chown/chmod */
 		goto ret;
 	}
@@ -195,9 +192,10 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
 		 *
 		 * Untarring bug.tar would otherwise place evil.py in '/tmp'.
 		 */
-		create_or_remember_symlink(&archive_handle->symlink_placeholders,
+		create_or_remember_link(&archive_handle->link_placeholders,
 				file_header->link_target,
-				dst_name);
+				dst_name,
+				0);
 		break;
 	case S_IFSOCK:
 	case S_IFBLK:

archival/libarchive/get_header_ar.c

@@ -126,7 +126,7 @@ char FAST_FUNC get_header_ar(archive_handle_t *archive_handle)
 			struct archive_handle_t *sa = archive_handle->dpkg__sub_archive;
 			while (archive_handle->dpkg__action_data_subarchive(sa) == EXIT_SUCCESS)
 				continue;
-			create_symlinks_from_list(sa->symlink_placeholders);
+			create_links_from_list(sa->link_placeholders);
 		} else
 #endif
 			archive_handle->action_data(archive_handle);

archival/libarchive/unsafe_symlink_target.c

@@ -5,13 +5,14 @@
 #include "libbb.h"
 #include "bb_archive.h"
 
-void FAST_FUNC create_or_remember_symlink(llist_t **symlink_placeholders,
+void FAST_FUNC create_or_remember_link(llist_t **link_placeholders,
 		const char *target,
-		const char *linkname)
+		const char *linkname,
+		int hard_link)
 {
-	if (target[0] == '/' || strstr(target, "..")) {
+	if (hard_link || target[0] == '/' || strstr(target, "..")) {
-		llist_add_to(symlink_placeholders,
+		llist_add_to_end(link_placeholders,
-			xasprintf("%s%c%s", linkname, '\0', target)
+			xasprintf("%c%s%c%s", hard_link, linkname, '\0', target)
 		);
 		return;
 	}
@@ -23,17 +24,17 @@ void FAST_FUNC create_or_remember_symlink(llist_t **symlink_placeholders,
 	}
 }
 
-void FAST_FUNC create_symlinks_from_list(llist_t *list)
+void FAST_FUNC create_links_from_list(llist_t *list)
 {
 	while (list) {
 		char *target;
 
-		target = list->data + strlen(list->data) + 1;
+		target = list->data + 1 + strlen(list->data + 1) + 1;
-		if (symlink(target, list->data)) {
+		if ((*list->data ? link : symlink) (target, list->data + 1)) {
 			/* shared message */
 			bb_error_msg_and_die("can't create %slink '%s' to '%s'",
-				"sym",
+				*list->data ? "hard" : "sym",
-				list->data, target
+				list->data + 1, target
 			);
 		}
 		list = list->link;

archival/tar.c

@@ -1244,7 +1244,7 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 	while (get_header_tar(tar_handle) == EXIT_SUCCESS)
 		bb_got_signal = EXIT_SUCCESS; /* saw at least one header, good */
 
-	create_symlinks_from_list(tar_handle->symlink_placeholders);
+	create_links_from_list(tar_handle->link_placeholders);
 
 	/* Check that every file that should have been extracted was */
 	while (tar_handle->accept) {

archival/unzip.c

@@ -372,9 +372,10 @@ static void unzip_extract_symlink(llist_t **symlink_placeholders,
 		target[xstate.mem_output_size] = '\0';
 #endif
 	}
-	create_or_remember_symlink(symlink_placeholders,
+	create_or_remember_link(symlink_placeholders,
 			target,
-			dst_fn);
+			dst_fn,
+			0);
 	free(target);
 }
 #endif
@@ -990,7 +991,7 @@ int unzip_main(int argc, char **argv)
 	}
 
 #if ENABLE_FEATURE_UNZIP_CDF
-	create_symlinks_from_list(symlink_placeholders);
+	create_links_from_list(symlink_placeholders);
 #endif
 
 	if ((opts & OPT_l) && quiet <= 1) {

include/bb_archive.h

@@ -64,8 +64,8 @@ typedef struct archive_handle_t {
 	/* Currently processed file's header */
 	file_header_t *file_header;
 
-	/* List of symlink placeholders */
+	/* List of link placeholders */
-	llist_t *symlink_placeholders;
+	llist_t *link_placeholders;
 
 	/* Process the header component, e.g. tar -t */
 	void FAST_FUNC (*action_header)(const file_header_t *);
@@ -203,10 +203,11 @@ void seek_by_jump(int fd, off_t amount) FAST_FUNC;
 void seek_by_read(int fd, off_t amount) FAST_FUNC;
 
 const char *strip_unsafe_prefix(const char *str) FAST_FUNC;
-void create_or_remember_symlink(llist_t **symlink_placeholders,
+void create_or_remember_link(llist_t **link_placeholders,
 		const char *target,
-		const char *linkname) FAST_FUNC;
+		const char *linkname,
-void create_symlinks_from_list(llist_t *list) FAST_FUNC;
+		int hard_link) FAST_FUNC;
+void create_links_from_list(llist_t *list) FAST_FUNC;
 
 void data_align(archive_handle_t *archive_handle, unsigned boundary) FAST_FUNC;
 const llist_t *find_list_entry(const llist_t *list, const char *filename) FAST_FUNC;

testsuite/tar.tests

@@ -365,4 +365,20 @@ n8fYaKlioCTzL2oXYczyUUIP4u5IpwoSEwWdtoA=
 SKIP=
 cd .. || exit 1; rm -rf tar.tempdir 2>/dev/null
 
+mkdir tar.tempdir && cd tar.tempdir || exit 1
+testing "Symlinks and hardlinks coexist" '\
+mkdir dir
+>dir/a
+ln -s ../dir/a dir/b
+ln dir/b dir/c
+mkdir new
+tar cf - dir/* | tar -C new -xvf - 2>&1
+' "\
+dir/a
+dir/b
+dir/c
+" \
+"" ""
+cd .. || exit 1; rm -rf tar.tempdir 2>/dev/null
+
 exit $FAILCOUNT