tar: fix a bug where autodetection messes up -z on extract

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 6 insertions, 4 deletions

diff --git a/archival/libarchive/get_header_tar_gz.c b/archival/libarchive/get_header_tar_gz.c
index b09f8691c..889fed0d9 100644
--- a/archival/libarchive/get_header_tar_gz.c
+++ b/archival/libarchive/get_header_tar_gz.c
@@ -9,7 +9,7 @@
 char FAST_FUNC get_header_tar_gz(archive_handle_t *archive_handle)
 {
 #if BB_MMU
-        unsigned char magic[2];
+        uint16_t magic;
 #endif
 
         /* Can't lseek over pipes */
@@ -21,7 +21,7 @@ char FAST_FUNC get_header_tar_gz(archive_handle_t *archive_handle)
 #if BB_MMU
         xread(archive_handle->src_fd, &magic, 2);
         /* Can skip this check, but error message will be less clear */
-        if ((magic[0] != 0x1f) || (magic[1] != 0x8b)) {
+        if (magic != GZIP_MAGIC) {
                 bb_error_msg_and_die("invalid gzip magic");
         }
 #endif
diff --git a/archival/tar.c b/archival/tar.c
index e9dc41fe1..1e3cecf44 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -1060,8 +1060,10 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
                         tar_handle->src_fd = tar_fd;
                         tar_handle->seek = seek_by_read;
                 } else {
-                        if (ENABLE_FEATURE_TAR_AUTODETECT && flags == O_RDONLY) {
-                                get_header_ptr = get_header_tar;
+                        if (ENABLE_FEATURE_TAR_AUTODETECT
+                         && flags == O_RDONLY
+                         && get_header_ptr == get_header_tar
+                        ) {
                                 tar_handle->src_fd = open_zipped(tar_filename);
                                 if (tar_handle->src_fd < 0)
                                         bb_perror_msg_and_die("can't open '%s'", tar_filename);