input/file: detect premature end of file

A bug report (https://github.com/MusicPlayerDaemon/MPD/issues/912) suggests that on Linux, reading on `cifs` files may rarely return 0 (= end of file) before the end of the file has really been reached. But that's just a theory which I need to validate, so this runtime check shall catch this condition before the assertion in DecoderBridge::Read() crashes MPD. Let's see. Closes https://github.com/MusicPlayerDaemon/MPD/issues/912

input/file: detect premature end of file
d9f9b3df · Max Kellermann · a43ee977 · d9f9b3df · d9f9b3df
Commit d9f9b3df authored Jul 01, 2020 by Max Kellermann
Show whitespace changes
Inline Side-by-side

Showing with 8 additions and 0 deletions

NEWS NEWS +1 -0

FileInputPlugin.cxx src/input/plugins/FileInputPlugin.cxx +7 -0

No files found.
--- a/NEWS
+++ b/NEWS
@@ -2,6 +2,7 @@ ver 0.21.25 (not yet released)
 * protocol:
  - fix crash when using "rangeid" while playing
 * input
+  - file: detect premature end of file
  - smbclient: don't send credentials to MPD clients
 ver 0.21.24 (2020/06/10)

--- a/src/input/plugins/FileInputPlugin.cxx
+++ b/src/input/plugins/FileInputPlugin.cxx
@@ -26,6 +26,8 @@
 #include "system/FileDescriptor.hxx"
 #include "util/RuntimeError.hxx"
+#include <cinttypes> // for PRIu64 (PRIoffset)
 #include <sys/stat.h>
 #include <fcntl.h>
@@ -94,6 +96,11 @@ FileInputStream::Read(void *ptr, size_t read_size)
 		nbytes = reader.Read(ptr, read_size);
 	}
+	if (nbytes == 0 && !IsEOF())
+		throw FormatRuntimeError("Unexpected end of file %s"
+					 " at %" PRIoffset " of %" PRIoffset,
+					 GetURI(), GetOffset(), GetSize());
 	offset += nbytes;
 	return nbytes;
 }