Check for IO stream failures in various format's truncate/seek operations

For the formats that support seek and/or truncate operations, many of
the C library calls used to determine or set the current position indicator
in the file stream were not being checked.  In some situations, if an error 
occurred, a negative value would be returned from the library call.  This
could then be interpreted inappropriately as positional data.

This patch checks the return values from these library calls before
using them in subsequent operations.

(issue ASTERISK-19655)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/1863/
........

Merged revisions 362151 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 362152 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@362153 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 12 insertions, 3 deletions

diff --git a/formats/format_h264.c b/formats/format_h264.c
index 155f46975..25ba54a77 100644
--- a/formats/format_h264.c
+++ b/formats/format_h264.c
@@ -140,10 +140,19 @@ static int h264_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 
 static int h264_trunc(struct ast_filestream *fs)
 {
-	/* Truncate file to current length */
-	if (ftruncate(fileno(fs->f), ftell(fs->f)) < 0)
+	int fd;
+	off_t cur;
+
+	if ((fd = fileno(fs->f)) < 0) {
+		ast_log(AST_LOG_WARNING, "Unable to determine file descriptor for h264 filestream %p: %s\n", fs, strerror(errno));
 		return -1;
-	return 0;
+	}
+	if ((cur = ftello(fs->f) < 0)) {
+		ast_log(AST_LOG_WARNING, "Unable to determine current position in h264 filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+	/* Truncate file to current length */
+	return ftruncate(fd, cur);
 }
 
 static off_t h264_tell(struct ast_filestream *fs)