xz: Fix a crash in progress indicator when in passthru mode.

"xz -dcfv not_an_xz_file" crashed (all four options are
required to trigger it). It caused xz to call
lzma_get_progress(&strm, ...) when no coder was initialized
in strm. In this situation strm.internal is NULL which leads
to a crash in lzma_get_progress().

The bug was introduced when xz started using lzma_get_progress()
to get progress info for multi-threaded compression, so the
bug is present in versions 5.1.3alpha and higher.

Thanks to Filip Palian <Filip.Palian@pjwstk.edu.pl> for
the bug report.

src/xz/coder.c

@@ -902,16 +902,19 @@ coder_run(const char *filename)
 				mytime_set_start_time();
 
 				// Initialize the progress indicator.
+				const bool is_passthru = init_ret
+						== CODER_INIT_PASSTHRU;
 				const uint64_t in_size
 						= pair->src_st.st_size <= 0
 						? 0 : pair->src_st.st_size;
-				message_progress_start(&strm, in_size);
+				message_progress_start(&strm,
+						is_passthru, in_size);
 
 				// Do the actual coding or passthru.
-				if (init_ret == CODER_INIT_NORMAL)
+				if (is_passthru)
-					success = coder_normal(pair);
-				else
 					success = coder_passthru(pair);
+				else
+					success = coder_normal(pair);
 
 				message_progress_end(success);
 			}

src/xz/message.c

@@ -56,6 +56,11 @@ static bool progress_active = false;
 /// Pointer to lzma_stream used to do the encoding or decoding.
 static lzma_stream *progress_strm;
 
+/// This is true if we are in passthru mode (not actually compressing or
+/// decompressing) and thus cannot use lzma_get_progress(progress_strm, ...).
+/// That is, we are using coder_passthru() in coder.c.
+static bool progress_is_from_passthru;
+
 /// Expected size of the input stream is needed to show completion percentage
 /// and estimate remaining time.
 static uint64_t expected_in_size;
@@ -241,11 +246,12 @@ message_filename(const char *src_name)
 
 
 extern void
-message_progress_start(lzma_stream *strm, uint64_t in_size)
+message_progress_start(lzma_stream *strm, bool is_passthru, uint64_t in_size)
 {
 	// Store the pointer to the lzma_stream used to do the coding.
 	// It is needed to find out the position in the stream.
 	progress_strm = strm;
+	progress_is_from_passthru = is_passthru;
 
 	// Store the expected size of the file. If we aren't printing any
 	// statistics, then is will be unused. But since it is possible
@@ -507,7 +513,15 @@ progress_pos(uint64_t *in_pos,
 		uint64_t *compressed_pos, uint64_t *uncompressed_pos)
 {
 	uint64_t out_pos;
-	lzma_get_progress(progress_strm, in_pos, &out_pos);
+	if (progress_is_from_passthru) {
+		// In passthru mode the progress info is in total_in/out but
+		// the *progress_strm itself isn't initialized and thus we
+		// cannot use lzma_get_progress().
+		*in_pos = progress_strm->total_in;
+		out_pos = progress_strm->total_out;
+	} else {
+		lzma_get_progress(progress_strm, in_pos, &out_pos);
+	}
 
 	// It cannot have processed more input than it has been given.
 	assert(*in_pos <= progress_strm->total_in);

src/xz/message.h

@@ -150,7 +150,8 @@ extern void message_filename(const char *src_name);
 /// \param      strm      Pointer to lzma_stream used for the coding.
 /// \param      in_size   Size of the input file, or zero if unknown.
 ///
-extern void message_progress_start(lzma_stream *strm, uint64_t in_size);
+extern void message_progress_start(lzma_stream *strm,
+		bool is_passthru, uint64_t in_size);
 
 
 /// Update the progress info if in verbose mode and enough time has passed