vcs-svn: cap number of bytes read from sliding view

Introduce a "max_off" field in struct sliding_view, roughly
representing a maximum number of bytes that can be read from "file".
If it is set to a nonnegative integer, a call to move_window()
attempting to put the right endpoint beyond that offset will return
an error instead.

The idea is to use this when applying Subversion-format deltas to
prevent reads past the end of the preimage (which has known length).
Without such a check, corrupt deltas would cause svn-fe to block
indefinitely when data in the input pipe is exhausted.

Inspired-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/vcs-svn/sliding_window.h b/vcs-svn/sliding_window.h
index ed0bfdd65c..b43a825cba 100644
--- a/vcs-svn/sliding_window.h
+++ b/vcs-svn/sliding_window.h
@@ -7,10 +7,11 @@ struct sliding_view {
 	struct line_buffer *file;
 	off_t off;
 	size_t width;
+	off_t max_off;	/* -1 means unlimited */
 	struct strbuf buf;
 };
 
-#define SLIDING_VIEW_INIT(input)	{ (input), 0, 0, STRBUF_INIT }
+#define SLIDING_VIEW_INIT(input, len)	{ (input), 0, 0, (len), STRBUF_INIT }
 
 extern int move_window(struct sliding_view *view, off_t off, size_t width);